Exercise Biology - The Science of Exercise,  Nutrition & building muscle

Main Menu

The Cause of Obesity

December 23 2011

Are obese people fat because they are lazy or because of their life style or their genes?

Now there is more and more evidence to suggest that obesity has a powerful genetic component and the cause of obesity is largely genetic.  Apparently, there is a powerful unconscious biological system that is constantly trying to keep your body weight within a certain range, say with 10-15 lbs.

the cause of obesity

What is the evidence that obesity is largely genetic?

Animal Studies: Animals which are tube fed, voluntarily eat less. When the tube is taken off, they voluntarily eat more and get back to the previous body weight. Animals that are restricted food, lose weight. But they quickly get back to their previous weight when food is re-introduced. Why?

It appears as if the animals were looking in the mirror and badly wanted to get back to their previous weight.

Adoption Studies: Obesity is said to run in the family. The usual retort for this case is that kids brought up in the same obese family are exposed to the same environment and hence not an example for the genetics for obesity. However, adoption studies clearly show that the adopted children's weight more closely resembles the biological parent than the adopted parent.

Twin Studies: Identical and non-identical twin studies are mainly used to study the genetic contribution for a particular trait like height, cancer, heart disease and so forth. Identical twins (Monozygote) have almost exactly the same genetic make-up. Non-identical twins (Dizygote), on the other hand, share about 50% of the genetic traits. It has been shown from twin studies that percentage of heritability of obesity ranges between 70 % to 80% - the only trait being higher than obesity is your height! See the picture below.

twin studies in obesity

Hormones: The recent discovery of leptin, ghrelin, bombesin and other appetite regulating hormones now offer a mechanistic explanation for how our body weight is so tightly regulated.
leptin treatment for leptin deficiency

  • Leptin: The discovery of Leptin is one of the greatest discoveries in the field of nutrition. Leptin is primarily secreted from fat. When you lose weight, leptin levels goes down and signals the hypothalamus to increase appetite and decrease metabolic rate. When you gain weight, leptin levels increase and in turn suppresses appetite. The picture shows leptin defiency treated with leptin administration. 
  • Ghrelin: Ghrelin is another hormone secreted mainly from the stomach. Ghrelin is a short term modulator of hunger; food intake decreases ghrelin, while starvation increases ghrelin.
  • There are other hormones like CCK, choleskylin, amylin and so forth that are part of a complicated network evolved to maintain the homeostatic control over your body weight.

Leptin Gene: Mutations in leptin gene, leptin receptor have shown to result in massive obesity. Mice with mutations in ob gene (leptin gene)  fail to produce leptin and show a fivefold increase in body fat compared with normal mice.  An as expected, these are remedied with leptin treatment. Unfortunately, majority of obese seems to be resistant to leptin. So injecting leptin to treat obesity didn't live up to the hype.

  • Other Genes: Mutations of other genes involved in energy balance has also shown to cause massive obesity.  Leptin receptors are located in the hypothalamus and lesions in these areas have shown to cause massive obesity and thinness in both animals and humans.

Stability of Weight: As most of us have experienced, our body weight tends to be pretty stable throughout the year. According to the laws of thermodynamics, you will stay at the same weight if you match your energy intake to energy expenditure.   That means, you somehow managed to spend exactly a million calories to match the million calories you ate throughout the year! 

Over a decade, people gain 10 pounds or so. This small increase means that you have precisely balanced tons of calorie intake and output to a precision level of 99.6%. This is almost impossible for even the most ardent calorie counter since most calorie count on food labels are off by 10% or more!

Extreme Variations: Environment is always blamed for obesity. If that is the case, why are extreme variations in fatness within the same fattening environment? Are all the lean people who live in the same environment watching their diet throughout their life?

In twin studies, it is very clear that for the same calorie intake and expenditure, people lose different weight. In one study where identical twins ate the same amount of calories in a controlled environment, the variation ranged from 12llb to 28 lb! So it is not always obese people eating more food.

Dieting: It is now pretty clear that 75-90% of the people who lose massive amount of weight (50-100lb) gain most of it back within 1-2 years.  It has been shown that when people lose weight, they not only feel hungry but that they also burn fewer calories than a person who is lean. The more you lose weight, the more the biological drive to gain the weight back.

Bariatric Surgery: Bariatric surgery is the most successful weight loss treatment. Bariatric surgery results in 20-40% initial weight loss; the majority of which is maintained for 15 years. It is now clear that bariatric surgery do not just work by making the stomach smaller. If that was the case, people could easily eat small frequent meals and get back to their weight; but they don't.

It has been now shown that bariatric surgery cures most people of diabetes. This cure happens a few days after surgery and even before they lose substantial amount of weight.  Bariatric surgery seems to change the gut biology to the extent that it somehow resets the homeostatic mechanism that controls body weight.

If it is mainly genetics, why is obesity on the rise?

And this is the main arguement against how obesity is largely genetics. Genes don't change so fast so how can obesity prevalanace increase? So it is mainly the environment - they say.

BMI: Obesity is classified based on Body Mass Index. BMI is measure of body fat based on your height and weight. If you are above 25, you are over-weight; 30 and above,  you are obese. This means that a small shift in bodyweight is enough to push a lot of people over the BMI category of obesity.

In 1999 a 33% increase in obesity was reported compared to the previous decade. In terms of body weight this just means a 3-5 kg increase in body weight. The 3-5 kg increase in bodyweight gives an entirely different picture than when you hear about a 33% increase in obesity!

Also the BMI of people between 15 & 30 hasn't changed much. What is going up is the BMI of people who are around 30BMI & over. The obese people are gettng more fat and making it look like everyone is getting obese, when it is clearly not the case.

What about the role of environment?

Gene-Environment Interactions: There are certain high risk groups such as the pima Indians and Pacific Islanders who have genes that are very susceptible to obesity. Pima Indians have an extremly high rate of obesity. For people who already have the obese genes, environment plays a permissive role. Environment is necessary, but not sufficient for obesity.

Overweight: For people who are moderately overweight like the majority, environment does play a role in the 5-10 lbs they gain over decades.

What about people who lose a lot of weight and keep it off?

These folks are clearly the minority, around 5-10%. It is not exactly clear how they do it. There might be a subset of people whose conscious motivation can override their biological drive in the long run. Majority of the people can’t.

Practical recommendations

1. We should focus more on health than weight or the cosmetic aspects.
2. It is clear than moderate weight loss of 10-15 lbs of weight loss in obese people can have dramatic improvements in their health.
3. It is also very clear that eating healthy and exercising has a beneficial effect on health independent of the change in body weight. 
4. The major cause for obesity is your genes and not the lack of will power or lifestyle.
5. Obesity is not the fault of obese people. So treat them with respect.

Here is part 2: The cause of Obesity- Part 2

If you like it, please share it:

Related Articles

Karky | Fri December 23, 2011  

I think the whole genes vs environment debate going on everywhere is a bit misplaced. We should focus more on the interaction between the two than one or the other. Obese people are probably genetically predisposed to obesity and since we have a surplus of food many places in the world those genes shine through on more people. Also, you could say genes play a premissive role since the environment needs to be obesity inducing and the genes just lie there in the background. IE, that argument can be used both ways.

I think another interesting debate on the cause of obesity is the whole energy expenditure vs energy intake. For example, it has long been known that obesity correlates with inactivity, but longditudional studies actually showed that obesity came before inactivity!

On another interesting note. I was just at a conference where Stephen Blair (renowned epidemiologist) was speaking and he had some interesting studies showing fitness to be more important than fatness.

I’ve heard the argument with obesity rates being misleading before. Some actually say there is no increase or obesity epidemic since an x% increase in obesity doesn’t have to be a big change in body mass (say if a lot of people in the overweight group gained a few kgs and ended up in the obese group) and another argument that when looking at the obese you’re just looking at the end of the normal distribution and even if that doubled it still wouldn’t be a lot of people.

However, a few kgs can probably play a pretty big role in health and we don’t only see movement from overweight to obese, we see it from normal to overweight as well, so I think the raise is pretty alarming. And for the second argument I’ve heard thrown around: the obese portion of the normal distribution is no longer small. so an x% increase is actually quite a lot of people..

As for obesity not being their own fault, I kind of disagree. Sure they can be genetically predisposed, but very few people have 100% determined obesity (leptin receptor mutations, etc). We have to remember that when we look at heredibility we look at the percentage of obesity explained by genes in the study sample. If you changed the environment, the results would be different. If you study twins, the variation in a trait will be due to the environment, if you study (hypothetically) individuals with the exact same environment all of the variation will be due to genetics. If you study a trait in Norway, a lot of it will probably be due to genetics, because we have a pretty similar environment, we don’t have a huge difference between the rich and the poor, etc. However, if you added any 3d world country to the sample, the heredability would probably go down, because you are introducing a larger environmental variation in the sample. I think that as a population gets more and more equal rights, you are no longer born into your station, etc, more and more of any trait will be explained by genetics, because people pretty much have equal opportunities to get education, buy proper food, etc
If two subjects with the exact same environment (hypothetically) were both fat and it was 100% explained by genetics, one of them could still change his/hers environment and lose weight while the other did not.

Now obviously, some people are probably more genetically predisposed to changing their own environment by changing their diet, physical activity level, etc. But I don’t think we are just gene controlled machines.

Another long and messy post, hope it makes somewhat sense :p

Mark | Fri December 23, 2011  

Don’t rat studies show that if they’re fed pellets they’ll maintain weight, whereas if they’re fed “highly palatable” foodstuffs (more akin to our human environment) they’ll gain…?  Think this was mentioned in the book “The end of overeating” by David Kessler.

Fast, cheap, comfort food plus increasingly sedentary lifestyle is the main driver here.


Anoop | Fri December 23, 2011  

Hi Karky,

Thanks for the good comments.

I don’t think I am saying environment doesn’t play a role at all and it is all genetics. The question is what is the largest contributor: And it is clear that it is your genes.

Your height has an interaction with the environment too. The average height has gone from 5 8 till 5 10 from the 1800 too the 1900.  Nutrition and other factors determine how tall you get. But still nobody doubts the heritability of height, do they?. The heritability of height is 90%. Of all the heritable traits, obesity is the highest recorded heritable trait - only second to height!

Sure the environment do play a role in the 10-15 lb gain people experience. And most people are thinking about this and just casually extrapolating to the obese. This is completely different for an obese person who is 50-100 lbs overweight. I am just below being overweight and I have to gain 45 lbs to be obese!

Of course, nobody will gain weight if you stop feeding them. Environment is a necassary condition for obesity, but not sufficient. What explains the 150lb guy and the 350lb guy within the same environment?

Single gene mutations account for 5-10% of the massive obesity and are pretty rare. The rest could be due to due to a single gene mutations of genes that are unidentified or/and complex interactions involving several genes and environment.

And your genes doesn’t just sit there in the background silently waiting for you to eat. There is a powerful unconscious biological drive to get to your pre-determined body weight that is not under your conscious control. And this is what happens when obese people lose 50-60 lbs. The hunger they experience is unimaginable. Dr. Friedman who discovered leptin writes that the drive to eat for someone who lost a lot of weight is “analogous to consciously holding your breath; inevitably, your basic drive to breath dominates your conscious motivation”.

Karky | Sat December 24, 2011  

Genetics is the larges contributor to the variance in body weight seen in todays world with todays environment. If the environment changes, those numbers will also change (or rather if the variability in the environment changes)

Is that 90% of height explained by genetics in industrialized nations, developing nations, or both combined? Because those 3 would probably have a bit different numbers since the variance in the environment probably differs quite a bit. For example, in wealthy countries most citizens probably get what they need to reach their “genetic height”, while in other countries fewer people might get what they need, leading to a lesser part of the variation being explained by genetics.

Of course the environment plays a role in those gaining 45lbs becoming obese, if they didn’t have food, they wouldn’t get obese, you said this yourself.

“What explains the 150lb guy and the 350lb guy within the same environment?”
- genetics, since they have the same environment. Now what explains the adopted twins with different body weight?

All these questions can be posed both ways, because genes and environment work together.

The drive to eat probably is the genes that drive some people to get overweight in an environment that allows it. However, those genes can also be said to be what allows some people to get obese when they are introduced to an environment that has a surplus of easy to access food. Environment is necessary, but not sufficient for obesity, but that goes for genetics too.. necessary, but not sufficient, because if your environment doesn’t have easy to access food, you still won’t get fat. You could even argue that some people can become obese in a food surplus environment even without having genes that are particularly predisposing.

All this being said, I’m kind of playing the devils advocate here. I completely agree that getting people to go around being hungry can’t be done, choosing to eat less is really difficult, at least for most people. Also, one person can’t actually change the environment they are in that much, food will still be easy to get, even if you know you shouldn’t eat it. Maybe if you isolated yourself on a secluded island somewhere, you’d manage to drop weight :p but the truth is, we live in an environment with a lot of food and there’s nothing we can do about it.

I just think that people blame the genes way too easily without knowing or thinking about the points I’ve brought up in this discussion.

Randy | Sat December 24, 2011  

Anoop and Karky,

I believe you guys are bringing up the same points from different perspective.  I agree with both of the sentiments here.

What is most important thought is what is the solution?

Anoop gave a basic framework of understanding obesity.

It’s apparent that one of the solutions is not get overweight/obese in the first place and create a “set point” for your body to maintain <—-This goes for people who are on that border of normal to overweight, etc.

Now what do we do with people who are overweight or obese already?

That in itself is a huge debate from cognitive psychotherapy to extreme measures like bariatric surgery.

However, the first thing which you guys have done so well is provide education in understanding what people are up against.

The second things is to teach people to control what they can. Exercise, physical activity, food intake etc etc.  Genes are gene, unless we die and get reincarnated we can’t do anything about it.

But like Marky said, we could do things as to not have the genes be fully expressed. 

This is a huge dilemma and understanding and education is key.  In America to many people are concerned with the cosmetic appearance like Marky said.  For obese individuals we have to focus on the health benefits of proper eating and activity.  The cosmetic things will take care of itself just not at the rate and expectations that people have.

Nice job guys,
Randy Gruezo

P.S. Nice job on summarizing research out there as I read Mark Young’s series on obesity that was comprehensive.  Your post is like the “cliff note” version of Mark’s grin

Hristo | Sat December 24, 2011  


the general figure of 5-10% weight loss success is misleading. I know a few trainers who get at least 50% or more success rate with their overweight clients.

It is all about how you sell what needs to be done, finding the right approach to limit food (calorie counting, intermittent fasting, low carbing, whatever is likely to work best for that specific client), the environment (train with ex-fatsos), the mindset you have. I think it has nothing to do with genes.

A little off topic. We have a well-known professor here in Bulgaria, who in the 80s gathered groups of elder people and trained them with deadlifts, squats and bench presses. All of them trained in groups with other older people and the professor. They got remarkable improvements in health, fixed a host of illnesses, got their backs straightened and what not. The drop-out rate was remarkably low (as long as the subjects lived in town and could come to the sessions, they didn’t miss workouts). They got the correct environment (train with other old people, some of them used to be national level sportsmen in their youths). They got to see the results and improvements from other people. There was even a 96 year old man squatting, deadlifting and benching a few times per week. Now, try to sell that idea to a “general” population of over the 60 and the success rate would be close to 0. Bad genes, I know wink

We, Bulgarians, have long ago accepted that environment is close to 100% of importance and used that in our educational system (sports schools, math schools, early specialization, frequent tests/exams/competitions and whatnot).

Karky | Sat December 24, 2011  

A lot of people manage to lose weight, the success rate is really who manages to keep it off. So a trained can probably get 50% of his clients to lose weight, but you need to come back 5 years later and see how many kept it off.

Hristo | Sat December 24, 2011  


I am talking about long term weight loss success rate.
btw. Out of all the people who try to lose weight, no many manage to lose a lot and from them not many manage to keep it off, generally.

I think at this moment in time, it is becoming easier and easier to lose weight and keep it off. That’s because the environment is becoming more friendly to the task with so many people training, dieting, reaching goals, serving as inspiration etc.

Or maybe I don’t live in the real world, as most of my friends train hard and know what to do. My experience may not apply to other people.

Anoop | Sun December 25, 2011  

Hi Randy,

Thanks for the comment!

Most people think that obesity is treatable. But the studies show otherwise. People who say it is about about self control and environment are always the ones who were born lean.

As I said 15-20 lb losses are attainable and have tremendous health benefits.


I wrote in the article about why some seem to lose a lot of weight and keep it off.The national weight control registry is a good example.


I am not sure where you are going with this.

Even if obesity is 100% heritable as seen in the leptin deficient kid, are you going to still argue that it is because of environment that they ate and got fat?

Karky | Sun December 25, 2011  

If they didn’t have food they wouldn’t eat, even if they have some mutation dealing with leptin. However, that’s pretty extreme. I think I’ve explained pretty well where I’m going with this. The whole x% explained by genetics is often oversimplified. If you look at a population who live in a similar environment, then a lot of the variation in traits must be explained by the genes, because the environment doesn’t vary. In order for the independent to actually explain the dependent, it must vary.

Anoop | Mon December 26, 2011  

If they didn’t have food they wouldn’t eat, even if they have some mutation dealing with leptin. However, that’s pretty extreme. I think I’ve explained pretty well where I’m going with this.

You haven’t explain much. All you have only said environment is required, and I don’t think anybody is disagreeing with it. Just saying that they wouldn’t have gained 45lbs, if they didn’t have food to eat doesn’t add anything sensible to the argument.  It is as senseless to say if there was not soil, no seed would grow, if Michael Jordan was born in Mars, he wouldn’t have been this great! This is not an example of gene-environment interaction, it is an example of a complete lack of environment. There is no environment to interact.

When we say gene-environment interaction, you look at the same genes in different environments and dissimilar genes in the same environment.  And this is what MZ Tins and DZ twins are used to study these.

I agree that contributions would be different in developed and developing countries. But the variations still exist within the same populations. You still find obese and lean people in developing and developed countries. Heritability is always looked at within the same population and not across.

And the second problem: You said obesity will not be manifest if the environment doesn’t have easy access to food. This is the fundamental difference between traits like obesity and height or IQ. As I said, there is a powerful unconscious drive that comes out as a voracious appetite to eat. Genes are not sitting there silently until they see food. These people cannot help but eat. People always think genetics for obesity means a “slow metabolism”. We know from the leptin deficiency cases studies that the first thing that happens with leptin injections is a tremendous drop in hunger. They lose weight by not eating food because they are not hungry. The same happens with bariatric surgery. An example is the with Prader-Willi  syndrome where they eat even from the garbage cans. Their families have to keep the refrigerator and cupboards locked because these kids cannot control. We also now that people can eat the same amount of food and can gain different amounts of weight.  We also know that people can do the same amount of exercise and calorie restriction and lose dissimilar weights.

I just think that people blame the genes way too easily without knowing or thinking about the points I’ve brought up in this discussion.

I think you are just completely and totally wrong.

I have been working in this field for 10 years and I have never heard someone say it is their genetics. Usually they say they have ‘hypothyroidism’ . There is complete lack of the understanding of heritability in the discussion of obesity. Even obese people think it’s a personal failing and have no clue it could be a heritable trait. They lack self esteem and confidence because all they hear from these smart trainers and dieticians is it about lifestyle changes and bla blah. They are discriminated at every walk of their life because people wrongly assume that obese people are lazy, undisciplined,and lack restraint and moral choices.  I know some of my clients lie to me because they are embarrassed and humiliated to reveal that they failed again.

What you see is the endless list of diet and workout books which argue that you were fat because you had too much fructose or sugar or fat or carbs or the missed breakfast or your lifestyle. Obese people are fat because they eat too much and do less activity.  All these articles say is how they can they eat less and be more active than why they are eating more and being less active in the first place!

Karky | Tue December 27, 2011  

that must be some difference between our contries then, because here everyone assumes it’s all genetics. At least that’s what it seems. And you’re not getting my arguments at all, I was just trying to make a point, but I give up.

Anoop | Wed December 28, 2011  

Hi Karky,

Some of the points you make are the ones everyone make: Environment is required and both environment and genetics play a role. I don’t think anyone is disagreeing with it. The usual response to questions like these “they all contributes”.If anything else, we are asking which contributes the most.

Most people from what I have seen takes personal examples of how they or other people gained 5-10lb or how they lost 5-10lbs and just casually extrapolates it to obese people. The degree of comparisons is just completely off here.

As I wrote I am slightly below of being overweight. If I want to be obese, I have to gain around 50 lbs! I eat a lot more than I would to maintain muscle, but I forever can’t imagine eating to gain 50lbs.  Now think eating like that for the rest of my life! Now think about people who are 100-150lbs overweight. Obesity just don’t happen by accident.

And to be honest, you have brought up good points about twin studies that most people never seems to think of about obesity. Everyone thinks about their personal life and comes up with some strange scenarios to explain obesity. WE clearly know that THE BEST way to study heritable traits is to look at twin studies. So why not look at them and try to explain obesity? And you have done that very well. And I am sorry if my post sounded a bit harsh.

If anyone argues that it is not heritable when the twin studies shows otherwise, we have a bigger problem here. They will have to explain why these classic twin studies employed by scientists for decades to study heritabilty are wrong!

I hope you see where I am coming from.

Hristo | Wed December 28, 2011  

Let me put it this way.

If you lift weights, you build muscle. Genetics play a good part in how much and how quickly you can build muscle.

Now, are genetics the *cause* of being pencilneckish?

Isn’t the focus on genetics as a “cause” just an excuse to be fat? Hey, my genes make me obese. I can’t do anything. Isn’t it better to have a mindset of “Hey, my genes may be crap, but I can workout and diet and do a damn good job of looking decent”.

Which is the more productive way of looking at it? And how about the question: “What is the cause of being lean and in shape?”.

Guillermo Chussir | Thu December 29, 2011  

What about people who lose a lot of weight and keep it off?
These folks are clearly the minority, around 5-10%. It is not exactly clear how they do it .There might be a subset of people whose conscious motivation can override their biological drive in the long run. Majority of the people can’t.

I don’t think most people fail to keep the weight off just because they feel a biological drive to get fat. I think most people just diet and exercise until they get lean and then they just go back to their original bad habits.

Mark | Thu December 29, 2011  

“I think most people just diet and exercise until they get lean and then they just go back to their original bad habits.”


Anoop | Thu December 29, 2011  

H Hristo,

Did you read my practical considerations? This a really great article in the New york Times just posted yesterday:
The Fat Trap

I have the conclusion of the article here. Here is your answer.

So where does that leave a person who wants to lose a sizable amount of weight? Weight-loss scientists say they believe that once more people understand the genetic and biological challenges of keeping weight off, doctors and patients will approach weight loss more realistically and more compassionately. At the very least, the science may compel people who are already overweight to work harder to make sure they don’t put on additional pounds. Some people, upon learning how hard permanent weight loss can be, may give up entirely and return to overeating. Others may decide to accept themselves at their current weight and try to boost their fitness and overall health rather than changing the number on the scale.

For me, understanding the science of weight loss has helped make sense of my own struggles to lose weight, as well as my mother’s endless cycle of dieting, weight gain and despair. I wish she were still here so I could persuade her to finally forgive herself for her dieting failures. While I do, ultimately, blame myself for allowing my weight to get out of control, it has been somewhat liberating to learn that there are factors other than my character at work when it comes to gaining and losing weight. And even though all the evidence suggests that it’s going to be very, very difficult for me to reduce my weight permanently, I’m surprisingly optimistic. I may not be ready to fight this battle this month or even this year. But at least I know what I’m up against.

Swapna Mazumder | Thu December 29, 2011  

Hi Anoop, 

Great article that supports what I experienced this year.  I started off this year with a lifestyle change in fitness and diet as my BMI was in the obese range.  I managed to lose 15 lbs over the year with many ups and downs.  Although I fell short of my goal of wanting to lose 25 lbs, or more importantly reduce % body fat from 26% to ~15%.  I am happy with my weight loss since I realized that inherited genetic traits such as hypothyroidism had a huge effect on how successful I was.  My goal for next year is to do everything I can to reduce waist size(visceral fat) as that has great health implications in the South Asian population.  Basically the key for me was to completely focus on nutrition, cardiovascular fitness and strength, btw the article on pain perception helped greatly in overcoming some of the barriers I had to exercise.

Thank you, the information you put out is so helpful.  Best wishes for the new year.

Anoop | Fri December 30, 2011  

Hi Gullermo and Mark,

It is crystal clear in studies that dieting or exercise or whatever 1s not working for obesity. The majority of the people gain almost most of their weight (90%). Exceptons don’t change the generality.

It s not that they oneday they all decided that they are happy to look fat again that they stoped exercising and dietng. It is because they CAN’T. 

Here is an experiment: Try losing 30 pounds and keep it off for 2 years. If you think that was hard, think about dong it for your whole life. Ask bodybuilders who lose 10-20 lbs for a few weeks and who clearly know this is only for a few weeks and they will tell you how hard it is.

Guillermo Chussir | Fri December 30, 2011  

I understand that most people end up regaining most of the weight they lost. But, I don’t think all those people regain all that weight just because of genetics.
I understand genetics makes it harder to stay lean for these people. We can’t change genetics, but I believe we can change habits. Of course It’s still posible to overeat on a good diet (like, with lots of veggies, whole foods and some cheat meals) and some exercise, but It’s gonna be harder than just returning the bad habits that made you fat in the first place.

I would like to know how many people try to keep a good diet and a good exercise routine after reaching their target weight. I don’t know any statistics about this. But personally, I don’t know many people that do that.

Anoop | Fri December 30, 2011  

You know that there are a lot of people who eat bad and don’t exercise, but are not obese right?

And as I said, genes are’nt silently sitting in the background. These genes do their work by increasing appetite , slowing down your metabolism, making you think about food and so forth. The system is protected by multiple ways. Genes are driving behaviors.

Or do you think obese people are just lazy, incapable of changing habits and behaviors unlike the leaner ones. If that’s the case, this would be one heck of a discovery in the field of human psychology.

Guillermo Chussir | Fri December 30, 2011  

I don’t think obese people are lazy or incapable of changing habits. I think most of them they don’t even try to change their habits. But I don’t think It’s their fault, propably no one told them that the best way to get lean and stay lean is to gradually change your habits. Probably the only thing they read or hear about is short-term solutions.

I understand the power of genes, but I still believe we can ‘trick them’ to a certain degree.

Anoop | Fri December 30, 2011  

There are 100’s of studies which have looked at diet, exercise, behavioral strategies, medications and they all combined.So we have tried it all.I am not looking around and making these statements.

The question is how do you trick them? Or even better how much weight loss do you need in the first place? Are your goals dictated by cosmetic apsects or health?

Guillermo Chussir | Fri December 30, 2011  

We know that some foods satiate better than others, and that kind of stuff. But, well. You said we have tried it all.

Let’s see if I fully understand what you are saying:
- Obesity is largely genetic. So, most obeses can’t get lean without herculean willpower.
- Obeses shouldn’t get so fixated in getting lean or ripped. Instead they should focus on being more healthy.

If so, I guess you are right.

I have one question. How much weight an obese can expect to lose permanently?

Anoop | Fri December 30, 2011  

Obesity is largely genetic. So, most obeses can’t get lean without herculean willpower.
- Obeses shouldn’t get so fixated in getting lean or ripped. Instead they should focus on being more healthy.

Exactly. As I wrote, you can move 10-15 and still be in your set point zone. These are just rough estimates. The number usually quoted in research is 10%. But this has been shown to be hard to maintain. Most gain it back within 3-5 years. If you can maintain it without a problem, you can always lose more.

We should stop saying that obese people can only be called normal if they come back to normal BMI. This takes people to acknowledge the fact that there are things beyond our control. That is not going to happen I think. You seem to get it though.

Anthony | Sun January 01, 2012  

Watched a show one night covering an experiment.  The details of which are just from my memory.

They took about 10 people from what looked liked a university environment.  Ages less than 30 years.  These people fit the category of those who said that they don’t put on weight no matter what they eat.

The experiment lasted 4 weeks.  These people had to eat double the calories they would normally eat. That was monitored, as well as their weight, girth and percent fat. They were also forbidden to exercise.

Results according to me; was that different people had different strategies to deal with the extra calories.

First strategy: Some people converted the extra energy into fat. Those who did added 4 kg per week, each week for 4 weeks.

Second strategy: One person just could not keep the food down.  This guy physically could not eat the amount of food needed and may have even been sick. He did not put on any fat at all.

Thirds strategy: Two girls ate all of the calories but did not add any weight at all.  The scientists didn’t know why but guessed that the reason why may have been that their bodies increased their fidgeting to burn off the extra calories.

Fourth strategy: A Chinese guy added weight but no fat.  The weight was muscle.  muscle costs more than fat, so the strategy his body used was to add muscle.

Four weeks after the completion of the research; the team went back to look at the 3-4 people that added body fat.  These people had lost all of the added fat without doing any exercise.  They just returned to their normal diet.

At the end of the show, they looked at one anonymous obese person why was held in hospital.  They restricted his calories until he lost 10% of his body weight. Then they put him in some kind of scanner to look at his brain waves.  What they said was, that he was still obese but according to his brain, he was starving.

Anoop | Sun January 01, 2012  

H Anthony,

Thanks for the comment. And I have seen that documentary just can’t remember. Where did you see it?

In fact it is shown in MS twins that there a wide variation in body weight gain for the SAME caloric intake and expenditure. In on study, the variability ranged from 13 lbs to 28 lbs! SO this is the reason some find it hard to lose and some find it easy. So it is not just that people are eating too much food.

GChussir | Sun January 01, 2012  

That happens in identical twins?
So weird. One would expect them to have the same reaction to overeating.

Anoop | Sun January 01, 2012  

No, it is between pairs and not within pairs. In fact one study showed a 13 times more variability between pairs than within pairs.

If it was within, then we could say it is due to unshared environment(intrauterine) and not genes.

Anthony | Mon January 02, 2012  

Hi Anoop,

It was just a show on TV one night here in Australia. It might have been on 3 months ago.

Personally I have no problem believing that the main cause is genetic. A lot of people say that the main cause is diet.  I am sure diet plays a large role as well. To refer to genetics though seems taboo. 

On the point of diet; sugar seems to be something a lot of people agree on.

One observation I have seen here in Australia is with Chinese people. They love to eat sweet breads and the result is a very big increase in body fat. I lived in China for 2 years traveling to many regions. Those there working in the local governments entertain a lot and drink a lot.  They too are fat.

Personally I can’t seem to influence my weight or fat levels with diet and exercise. Neither a reduction or an increase.

A related topic, perhaps, I would like to ask you about Anoop. Here in Australia at least, the government is trying to reduce the incidence of obesity through encouraging diet and exercise involvement. I think they should be encouraging people to build muscle rather than lose fat. I think that advice would achieve all of the same benefits as the weight lose message but have additional benefits.  I would like to ask what your thoughts are on this.

Anoop | Mon January 02, 2012  

Hi Anthony,

It is not about personal opinions. It is what science shows.

And as I wrote, what people think is an obesity epidemic is 10-15lbs increase in weight. But is enough to push a lot of people over the 30BMI mark. And from 2000, the increase has plateaued. Most people think of population data and extrapolate it to individuals. If you think about it, how many people who you know have gained 50lbs? Obese people were always obese and lean always lean.

That is a good point.  There is some evidence of increasing muscle is what accounts for the decrease in mortality in obese people. We know that waist circumference is also good indicator. Hence BMI is usually combined with waist circumference because people with LOW BMI can have a large circumference.

The hard part is how to measure muscle mass in thousands of people. These prospective studies need thousands of people to measure mortality and such. If we find a correlation, then we have to do a RCT’s which s super expensive. Just to give an example the diabetic prevention trial which was run for 3 years with 4000 people cost 182 million!! Then we will have to make sure this is not confined to one ethnic group and gender and such.

And that’s how science works.

Note: You can register in the forums Anthony. It also lets you post comments without waiting for moderation.

FullDeplex | Tue January 03, 2012  

‘Note: You can register in the forums Anthony. It also lets you post comments without waiting for moderation.’

I commented in this article, but my comment did not show (after moderation).

Anoop | Wed January 04, 2012  

Hi Depelex,

When did you post? Did you post after the I posted the reply to Anthony? I don’t remember deleting anything. Can you post again?

carey waiand | Wed January 04, 2012  

how come obesity genetics turn on so late in life?i started to get fat in my early 30,s,this has slowly increased to where i am now obese.i,m currently47 and about 90lbs over weight.
my experience was gaining weight as my activity went down.more sitting ,less moving more eating.i don,t think i had a “genetic shift” in my early thirties.i think i got lazy and ate more.

if i think back to how active i used to be and how little i ate or thought about food,man what a change.but becoming obese does drive apetite because you are larger,more to maintain.

i,m in the sloth and gluttony group for sure.i don,t buy that my lean body of 30 years suddenly switched on some"you will now be obese"gene.

Viktor | Wed January 04, 2012  


Been following your blog for quite some time and I generally like it. However, and if you posted it I am sory, what are your sources for genes bearing the biggest impact on obesity? As a student of molecular biology, with genetics as my major, I would appreciate a scientific source for that claim.

Anoop | Thu January 05, 2012  

H Carey,

Thanks for the comment. There are always exceptions. Exceptions, as the name suggests, are just exceptions. They don’t change the generality. 

Hi Viktor,

Thanks for the comment.

I hope you read the article. It is largely from the twin studies which looks at the heritability of a trait. I can get you the studies if you want to.

Sheay | Thu January 05, 2012  

Anoop- So would you say it’s a safe bet that around 90% of the next generation (in the US) is going to be obese? Genetic information can be altered from diets and fitness regimens. If you’re saying inactivity and calorie intake are not the largest contributors to obesity I’m going to disagree. I can provide citations to the sources for the reasons I disagree. Again I think it’s important to consider that our diet and exercise choices effect our DNA so it’s misleading to say genetics is the largest contributor. I don’t remember the US having an obesity problem until somewhat recently. 

If you (or anyone for that matter) sat in your house and ate McDonalds for a month, refused to exercise, and only got up and moved around to get more food or go to the bathroom-There would be weight gain, (due to energy imbalance) no genetic predisposition required. The largest contributor to obesity is when the calories consumed exceeds the calories expended. It is not unrealistic to suggest that we are among a population (in the US) that is perfectly capable of taking this epidemic the other direction. Since you are familiar with how “science works” the saying correlation does not imply causation should hold some weight with consideration to this topic.

Anoop | Thu January 05, 2012  

Hi Sheay,

Thanks for the comment.

So would you say it’s a safe bet that around 90% of the next generation (in the US) is going to be obese?

No. In fact, the recent 2007-2008 obesity prevalence rates are showing that the trends are leveling off and are plateauing. This is the same for children and adolescent obesity. here is the reference: http://jama.ama-assn.org/content/303/3/235.full

Did you even bother reading the article?

When people say that the obesity rates have gone up, it is a population statistic. We are taking about 10-15lb per decade increase.But if you are just below that 29 BMI mark, it is enough to push a lot of over the obese mark.That does’t mean that people just became 50 lb heavier!

Viktor | Thu January 05, 2012  

Yes, I would appreciate that Anoop. I will then elaborate on why I do not think you’re entirely right.

FullDeplex | Thu January 05, 2012  

Hi Anoop,

I posted when there were only about 10 comments, so well before Anthony.

I did not copy it anywhere…

FullDeplex | Thu January 05, 2012  

I am also not getting the “someone responded to your comment” -emails for this article.

Mark | Thu January 05, 2012  

Anoop: “Try losing 30 pounds and keep it off for 2 years.”

Done and done.

Mark | Thu January 05, 2012  

This may be the show you’re thinking of:

Anoop | Thu January 05, 2012  

Hi Viktor,

Here you go: I am linking some of the well known studies whch are referenced a lot.


And look at all the other evidence i talked about in the article. The only counter arguement is the increase in obesity seen in the last decade. And I have explained the reasons why this may not be the case.

Sheay | Thu January 05, 2012  

Anoop—Yes, I read your article, enjoyed it, agreed with the majority of it, except that genetics are the largest contributing factor to obesity. I made that clear in my post. Since you seem to have made an astounding discovery through existing data you might want to shoot a letter to the CDC to let them know what the new largest contributing factor to obesity is. Your article portrays information contrary to what is currently widely accepted (scientific communities, medical, etc.) as the largest contributor to obesity. I’m not saying that genetic information does not play a large role in obesity. If the article portrayed that genetics predisposes a person to be more at risk of becoming obese I would agree. But that predisposition would require the correct environment (sedentary unhealthy lifestyle) for it to surface.

Obesity is a complex and incompletely understood disease. When you consider all the contributors to obesity (sleep debt, stress, inactivity, poor diet, genetic predisposition, economic, geographic, ethnicity, etc. etc.) it’s silly to single one out, put your finger on it, and say “I’ve got it!” I could quote stats all day making it appear that poverty and obesity go hand in hand, but both of us know that it’s more complicated than that.

Last I checked the most effective way combat obesity was through a life decision to make a healthy change by slowly adapting a healthy diet combined with adequate exercise. Which is something I think both of us will agree that most Americans don’t get enough of.

Do you relay information like this to your clients before you train them? Do you tell them that there’s nothing you can do to help them because they have a genetic affliction that is keeping you from training them? I sincerely doubt it.

Sheay | Fri January 06, 2012  






Some experts believe that as much as 80 percent of obesity is genetically linked. That doesn’t mean the genes cause obesity directly; rather, individuals who carry these genes are more susceptible to becoming obese.

“You need both the gene and an environment where plenty of food exists,” explains Kahn. “If these people lived in famine conditions, they probably couldn’t get fat.”

The excerpt is from the last link given. I think it highlights the crux of our disagreement. It also shows how a minor misunderstanding or a misplay with words can lead to a trivial false representation of the big picture. Obesity will most likely overtake smoking as the #1 preventable (key word there) disease in the coming years. I think what the data you posted warrants is more exploration into something previously considered fairly insignificant; which is what is happening.

The biggest issue I have with this article is when I consider how someone who is overweight or obese will react when reading this. It’s not absurd to consider that people could become fatalistic in their approach to weight loss upon reading the article.

Anthony | Fri January 06, 2012  

Hi Anoop,

I would like to respond to your comment (if you have time):

“It is not about personal opinions. It is what science shows.”

I think we can and probably should look at science but I think it is a big mistake to rely on science exclusively.  As a layman; here are a few reasons I believe this.

1. Science is more often wrong than right.  How often do we see research conducted on the same topic by different people with different results?

2. Good science depends on good scientists.  Just as in any field there are scientist strewn across the continuum of bad to good.  Who are the people conducting this research?

3. As we have seen in the areas of global warming and pharmaceutical research; there is corruption in the scientific research.


4. Research appears to me at least; restricted in it’s scope. We don’t often see enough research surrounding a topic that would allow development of a system? 

Also I would like to add a few links to what appears to be another reason for weight gain.


All the best


Anoop | Fri January 06, 2012  

Hi Shay,

You are making the same argument that everyone first jumps on to: Environment is required. And none in this world is disagreeing with you.

Karky was making the same and I replied to him. Nobody will get fat if you stop feeding them or tie their hands or send them to a concentration camp . But that is an example of a lack of environment. What we are concerned is why only a few people get obese when there is free access to food or when food is not restricted to everyone.

I am copying what I replied to Karky:  You said obesity will not be manifest if the environment doesn’t have easy access to food. This is the fundamental difference between traits like obesity and height or IQ. As I said, there is a powerful unconscious drive that comes out as a voracious appetite to eat. Genes are not sitting there silently until they see food. These people cannot help but eat. People always think genetics for obesity means a “slow metabolism”. We know from the leptin deficiency cases studies that the first thing that happens with leptin injections is a tremendous drop in hunger. They lose weight by not eating food because they are not hungry. The same happens with bariatric surgery. An example is the with Prader-Willi  syndrome where they eat even from the garbage cans. Their families have to keep the refrigerator and cupboards locked because these kids cannot control. We also now that people can eat the same amount of food and can gain different amounts of weight.  We also know that people can do the same amount of exercise and calorie restriction and lose dissimilar weights.

In an environment where is free access to food, the largest contributor is your genetics. This is not my opinion; these are from twin studies which are used world wide to study heritability. If it was largely environment as it has been shown for some of the other traits and diseases, we would see that. It is as simple as that!

And you must be kidding. The reference I posted is from Kartherine Flegal about how obesity is leveling off since 2000.  She is one who showed that obesity prevalence was increasing in the 1980 & 90’s and her studies are what we use to show these trends. If you don’t agree with this study, you better don’t agree with her previous studies about obesity increasing.

You comments about how to combat obesity, how obese will react ,what I recommend are all addressed in the article or in the previous comments.

Anoop | Fri January 06, 2012  

Hi Anthony,

Thanks! Science has a lot of limitations. I can even give better ones.

But we have no better option than science.

Sheay | Fri January 06, 2012  

Anop- I’m not jumping to anything you’re the one jumping and making bold claims with the utmost certainty that genes CAUSE obesity. Here is a simple but crude analogy that will hopefully get the point across. Fire needs three things in order to exist: heat, fuel, and oxygen. Intensity can be controlled by adjusting any of these three things. We could argue all day about which is the most important or largest contributor to fire but the point would be moot.

Genes don’t cause obesity, it’s that simple. Do they make someone more susceptible to becoming obese? Of course they do…maybe more so than previously thought-but to claim that genes cause obesity is absurd.

Like I said before, you might want to send a letter to the CDC or the WHO and inform them that the information their professionals are relaying is incorrect with regard to the actual the cause of obesity.

GChussir | Fri January 06, 2012  

I think Anoop never said that genes are the ONLY cause of obesity.

Of course, enviroment is necessary. But It’s a moot point unless someone is willing to live in a desert island.

Willpower and better habits can make you leaner and stay leaner than before. But the leaner you get, the harder It’s going to be.

Anoop | Sat January 07, 2012  

Yep, what GChussir said.

Sheay here is an example for you: Imagine you plant seqouia tree (one of the tallest trees) and other trees in a plot which has the same type of soil (the same environment). After a few years, you see the Seqouia tree taller than others. Are you going to say the difference in tallness of the trees is LARGELY because of the environment or the genetics of seqouia tree?

And about your comment about CDC. And what makes you think that nobody knows about the biological basis of obesity? Do you know why the weight loss percentage recommended is a very conservative 5-10%?  And topics like these are only seen in scientific publications than publications for the lay people for obvious reasons. 

The only argument against the genetics of obesity is the increase in obesity prevalence in the 1980 and 90’s, which is valid argument. And this is argument which is always put forward by researchers in most papers . If it is largely genetics, how can obesity increase in such a short period of time? Gnes don’t change so fast, hence researchers believe that it is caused by an interaction of environment and genes.

But this increase is a modest weight gain of around 5-15 lbs in decades! That modest weight gain is enough to push a lot of people over the the 30 obese mark. This is completely different by saying there is an “obesity epidemic”. And if you look at the prvelance tables, it is not everyone gaining weight equally. It is mainly people who are obese to begin with (>30). People who are in between 25 & 30 BMI, the obesity prevalence hasn’t changed at all for 30-40 years. But people think that just about everyone is blowing up.

Sheay | Sat January 07, 2012  

Different species of trees…not gonna work. Cute try though.

Viktor | Sat January 07, 2012  

Well, of course it comes down to genes at some point. But it is absurd to think that the reason america is so obese is because of their genes. Of course it is not. It is because they eat to much unhealthy food.

You have not provided any strong support for your conclusion that the main reason for obesity is genes, and not the environment. In fact, in a genetically diversified country like the US, that is an absurd conclusion, not based on available data.

I’m not saying genes don’t matter, of course they do, but in no way can you argue that genes are the MAIN reason for obesity. You have NOT presented any scientific evidence for that conclusion, especially not in statistical terms which is the only relevant method if you are to make sweeping, big conclusions like that.

Socioeconomic status has an impact:


Epigenetic effects established in the fetus (due to overeating) effects gen-transcription in adult life (thus, environmental strictly speaking):


There is a LOT of science on this topic, and your actually quite old sources seems more like cherry-picking than an actual scientific approach to the subject.

Anoop | Sat January 07, 2012  

Different species of trees…not gonna work. Cute try though


Great! We are getting closer. Now what makes different species different in the same environment?

Hi Viktor,

So you don’t have anything specific to say about the studies? Why even ask for it then?

There is a LOT of science on this topic, and your actually quite old sources seems more like cherry-picking than an actual scientific approach to the subject.

So you don’t like the studies because they are old. Are you kidding? Are gong to say the discovery of DNA is not valid since it was in 1957 too? Look at any review paper and these are the articles they reference because they are very well done by top researchers in that field.

Some of the studies are referenced more than 1000 time in the literature!. In fact, the Wardle study in 2008 prompted even an editorial to show even now the heritability of obesity is very high. This study was specifically done to see if in the current toxic environment will the heritability do down. But it didn’t.

Will socioeconomic status change it sure. But we are talking about a 10-15 gain in decades! First,we should understand the numbers and how they come with these numbers then make statements like “why America is so obese”.

And here are the twin studies on obesity in the last 5 years for you:I have even copied the abtract for you.

These results show the great importance of genetic factors in the eating behavior of a large, unselected population of young adult male twins.

Latent growth models revealed a substantial genetic influence on BMI level at baseline in males and females

Genetic analyses showed that genetic factors are the main contributors to variation in height, weight, and BMI, within both countries

Quantitative genetic model-fitting confirmed substantial heritability for BMI and WC (77% for both).

The h(2) estimates emphasize that body fat and distribution as determined by DXA scan are under extensive genetic control. http://www.ncbi.nlm.nih.gov/pubmed/16421348

The genetic contribution to BMI is strong during adolescence, and it mainly explains BMI phenotypic correlations across adolescence. Common environmental factors have an effect on BMI during early adolescence, but that effect disappears by late adolescence.

Sheay | Sun January 08, 2012  

If you were comparing the same species of trees in the same environment your comparison would hold water, but that’s not the case. The differences of the same species of tree, in the same environment (the same growing conditions) would have minor differences. Any major differences concerning tree growth within the same species would largely be due to environmental differences i.e. amount of sun exposure, soil conditions, water, etc. Are you trying to say there are different species of humans living among us?

Here are some interesting facts about tree growth. http://www.fathom.com/course/21701736/session5.html

Anoop | Sun January 08, 2012  

99.9% of the people would say the variation of trees within the same environment is largely explained by GENES. Sequia trees is genetically different than a pirch tree.

The same way the variation of body fatness within the same environment is largely explained by genes. A severely obese person is genetically different than a lean person.

People don’t say it is because there is abudant nutrients in the soil, abudant sunlight that the sequoa tree is taller than other trees. And you are repeatedly saying the same thing about obesity: It is because they had food to eat that they got fat.

If you cannot understand this simple analogy maybe this is not the right site for you to interact. This is my last reply to you.

GChussir | Sun January 08, 2012  

I understand this article may sound a little fatalistic and be hard to swallow.
But keep in mind that we still can make obese people lose weight.
We just have to be more realistic about how much weight.

I think it’s better to say “With a good diet and exercise routine, you’ll be stronger, healthier and happier”, than promising that they will look like Tyler Durden and watch most of them fail over and over again.

May be, the primary cause of someone’s obesity is non-genetic and he’ll be able to get the “Tyler look” without monstrous willpower. But the odds are low.

Anoop | Sun January 08, 2012  

Hi Gchussir,

The crux of your message is to make realistic goals based on health and not on cosmetic values. And if you wanna look great, go ahead and try it. Nobody is stopping you, but atleast now you will have a clear understanding of what you are up against.

I think this article will be most reassuring to obese people who are constantly blaming themselves for their failure. They are convinced that it is their fault because lean people always say it is all about “healthy lifestyle and choices”. People hopefully will look at obese people and atlast will understand their struggles and challenges for something which was never their fault. Hopefully, the obese people will realize that it not their personal failing and they are as hardworking and disciplined just alike everyone else in this world!

GChussir | Sun January 08, 2012  


You said 70%-80% of obesity cases are mainly genetic. What about the rest?
Do you know anything about psychological causes? How common are they?

Anthony | Sun January 08, 2012  

An interesting article.


Anoop | Sun January 08, 2012  

Hi Anthony,

Good question.

The rest of environment is divided into shared and unshared environment. Surprisingly, what we see is that the whole 20-30% can be explained by the unshared environment. Unshared environment means experiences which are unique to each twin. This means that either the obese twin is making choices which make them eat more food, choosing their activity patterns, or unknown factors like intrauterine differences and so forth. Genes are driving these individual choices. The same way one kid is always in the library while the other in the same family is always playing outside.

So the family or parental environment, socioeconomic status of the family, neighborhood shared by both the twins is not making a big difference. Shared environment has an effect in the early years, but this effect disappears as they reach adolescence and become independent. So not a great idea to blame parents for kids being obese.

GChussir | Sun January 08, 2012  

So the family or parental environment, socioeconomic status of the family, neighborhood shared by both the twins is not making a big difference.

That makes sense to me.
I know obese people claiming their parents made them obese. That’s nonsense. It’s not like they forced them to eat.

Viktor | Sun January 08, 2012  

Firstly, twin studies are quite controversial. And rightly so.

Secondly, are you saying the reason this is the BMI of the world: http://apps.who.int/bmi/index.jsp is because of the GENES and NOT the environment? You mean that the extreme environment in the US compared to the world is NOT the main cause of the obesity?

Are you even serious? This is bordering on pseudo-science and I will stop promoting and following your blog if you do not explain yourself.

Anoop | Sun January 08, 2012  

Hi Ghussir,

We all say that. In fact I wrote in the previous comments about how a family was about to lose their kid because the kid was severely obese and the social service group was about to take the kid away. The researchers intervened and told them that kid has a genetic disorder. t is like the Prader-willi syndrome - they have to keep the fridge and cupboards locked.

H Viktor,

I don’t think so. These twin studies are still carried out and are one of the corner stones of studying heritability. And I gave you number of reasons in the articles for the biological basis. Read the recent The Fat trap article by Tara Parker. It is very well written.

The 10-15 lb we gain in decades is due to the environment. I think you are missing the point. If you take all the population in US and plant them in a developing nation, there will be a 10-15 lbs drop in weight. But the shape of the BMI curve will still be the same. The obese people will remain obese, lean people will remain lean, albeit 10lbs lower. And I am writing an article about it soon. Also not everyone is putting on weight. It is mainly the people who are obese and severely obese category. If it is the environment, why are the 20 to 25 not gaining weight?

Sumith | Mon January 09, 2012  


VJ | Mon January 09, 2012  

great job Anoop this was the best article i have come across in my life.really enjoyed reading the comments and arguments. cant wait more to see fantastic articles like this from you .

Viktor | Mon January 09, 2012  

Well.. hmm, allright, I will look into this somewhat deeper when I have the spare time.

Sheay | Mon January 09, 2012  

I understood your analogy. You used two different species of trees to try and support what you are saying. Of course it’s genes if we are talking about two different species. We could talk about why whales and humans are different sizes, dandelions and monkeys. It is clearly differences in the genes. But within the same species? We are doing the same thing psychologists did for nearly a century with the nature vs. nurture argument. It is now widely accepted that it is nature(times)nurture. There are gene mutations that make obesity very hard to combat and gene mutations that that make it almost impossible for someone to gain weight. These mutations are exceptions to what is normal in society.

How much more sedentary have people become over the last century? How much more prevalent has unhealthy, processed calorie dense food become?

I’m sorry you don’t feel like discussing this topic any further but instead of blaming you for a lack of understanding I’ll just attribute it to a communication breakdown. The oversimplification of this topic seems to be a problem area. I am also not the only one who disagrees with you. Good day to you sir.


GChussir- Sorry I haven’t responded to any of your posts yet. The problem with something being fatalistic is that it’s just that-it’s fatalistic. You don’t explain a fatal car accident with expressions such as, “the passengers kind of died.” I used that word for a reason. I wasn’t saying that everyone that reads this article would just give up. I just pointed it out as a possible problem area. Those involved with research within the scientific community regarding obesity and genes have made the same concerned association(s) that I have.

I never claimed that Anoop said that genes were the single cause of obesity, but I do disagree that it’s the largest contributor period-especially considering how rapidly our environment has recently changed. I don’t think it’s a matter of “wanting to live on a desert island” but realizing that everyone is different and generalizations breed confusion and cause problem areas. People only being interested in weight-loss for cosmetic reasons is a problem area in itself (which Anoop covered). Deciding to live a healthy lifestyle is largely unimportant to a considerable proportion of the population, that is until those choices manifest themselves as health complications.

Gastric surgery has been successful for those who are severely obese. The largest change to obesity can be done through the adaption of a healthy lifestyle. The importance of a healthy diet and exercise during pregnancy wasn’t even mentioned. It’s kind of a big deal. Another large factor was stress.

GChussir | Mon January 09, 2012  


The CDC says:
“Recently, several independent population-based studies report that a gene of unknown function (FTO, fat mass and obesity-associated gene) might be responsible for up to 22% of all cases of common obesity in the general population. Interestingly, this gene also shows a strong association with diabetes. The mechanism by which this gene operates is currently under intense scientific investigation.”

You said:
“Dieting: It is now pretty clear that 75-90% of the people who lose massive amount of weight (50-100lb) gain most of it back within 1-2 years. “

Where does this figure comes from?

Harry | Tue January 10, 2012  

Clearly, genetic and environmental factors combine to determine if any given individual will become obese.  For some individuals with a strong genetic predisposition, even a non-obesogenic environment will provoke obesity.  For those with low genetic predisposition, only a very obesogenic environment will provoke obesity (e.g. regular cruise-ship trips).

At the population level, however, it would seem that the change in eating environments (the increasing palatability, decreasing cost, increasing social acceptability of ‘entertainment’ eating, and increasing availability of foods) is responsible for the increase in the rate and magnitude of obesity.

So, what causes obesity? For me, it may be one thing, for you another.  But at the population level, the recent increases (1980s onwards) are clearly environmental.


Anoop | Tue January 10, 2012  

Hi Sumith,

Thanks for the link! I am not sure if it was the obesity, but it is very well possible. It is just really sad. This is why it is so important understand the truth than sugar coat it.

Hi VJ,

Thanks for the comment!

Hi Ghussir,

Thanks! And now imagine how many other undiscovered genes are involved and how they all interact in different ways!

One of the frequently cited article is: http://www.ncbi.nlm.nih.gov/pubmed/2663745. Almost all reviews about obesity start with this statement.

Hi Harris,

Thanks for the comment.

If you think, just giving free delicious food will make you gain 50 lb, watch this video. http://www.youtube.com/watch?v=_6-A0iHSdcA . This is the experiment shows how hard it is to GAIN weight in normal people even if they are given free, delicious foods. They were working very hard to gain weight!

And I would ask you to read the comments. I think we talk about the contribution of genetics and environment.

Harry | Tue January 10, 2012  

Hi Anoop,

Given that the probability of any given individual becoming obese can be expressed as a function of ‘genetic predisposition x environmental stimuli’, it is to be expected that weight gain will not result solely from the introduction of palatable foods (presumably these subjects had already been regularly exposed to palatable foods prior to the experiment, and as such, there was little novelty in the exposure).

On the other hand, when (1) we introduce hyper-palatable “Westernised” foods to indigenous cultures that were predominantly lean, or (2) we follow a cohort of lean migrants from these cultures as they enter Westernised diet environments, we find that the rates of obesity rapidly increase in both cases.

To me, these facts speak powerfully to the relative importance of environment in promoting obesity.

If, as seems to be the case, genetics is a permissive factor in obesity, and environment is a regulating factor in obesity, then we would expect to see rises in the rates of obesity correlating with rises in obesogenic environmental stimuli. This is precisely what we are seeing worldwide.

If, on the other hand, it is genetics that is the regulating factor, we would expect obesity levels to correlate with the relatively static genetic record (thus leading to very slow and/or small magnitude changes).  This is not what we are seeing worldwide.


Anoop | Tue January 10, 2012  

Hi Harris,

Just novelty? Or the genes are keeping them bodyweight within in zone though multiple mechanisms like increased energy expenditure and decreased appetite and so forth.

Agreed.  And that is what I wrote about Pima Indians and certain other aboriginal groups.

For me and most people, both cases above are an example of how genes are driving weight gain. In one group, the same environment is dong nothing, but in an other groups it is making them fat.

Also even in the 1960’s when the environment wasn’t conducive, the shape of the curve was almost the same. There were obese people and lean people.

Let me put this way: If environment was the largest contributor, then the weight gain would be similar across the population and everyone would have got fat, right? But that is not what is happening .And my next article in on that.

As you said is the weight gain slow and of small magnitude changes? YEs. When we say the obesity prevalence increased by 33% in the 1990’s, the weight gain was just a modest 6-10 lbs!An this is mainly due to the obese and severely obese people gaining weight.

GChussir | Wed January 11, 2012  


“The direct genetic effect on obesity is estimated to be 25-40%. Indirect genetic factors raises the genetic effect to approximately 70% of the cause of obesity. Over 24 genes associated with obesity have been identified.”

Any idea on what “indirect genetic factors” means?

Anoop | Wed January 11, 2012  

Hi Gchussir,

Indirect effect means how others interact. For example, if you were born in a household where they restrict how much you eat, you will not have much food to be obese. The direct effect are hunger , metabolism and so forth. And the effects of indirect effect are more when you are a kid, but it becomes smaller as you get older. It is similar to how the shared environment gets lesser and lesser as they get older and don’t need to depend on others.

It is clear that the variation in any trait within an environment is mostly genetics. The question only arises when there is sudden increase in obesity which cannot be explained by genes. And even if there is sudden increase in obesity, the shape of the curve s still the same. There are still obese people and still lean people and still normal people as were in the 1960’s!

I am writing the second part which will explain the increase in obesity.

Viktor | Wed January 11, 2012  

You clearly do not have adequate understanding of how this works, hence you are a dilettant in this area. And I just stopped following your blog.

You should consider removing the science in your name.

Anoop | Thu January 12, 2012  

Hi Viktor,

Can you for heaven sake be more specific about where am I wrong rather than just making one line comments about how I am so wrong, my studies are old, you will look deeper when you have time and so forth.

The only thing clear from your post is your are a student with genetics as your major.

Viktor | Thu January 12, 2012  

Well, you should read Harrys comment a couple of times more. Your answer to that comment is unspecific at best.

At worse, you did not understand what he’s saying.

This in particular:

“If, on the other hand, it is genetics that is the regulating factor, we would expect obesity levels to correlate with the relatively static genetic record (thus leading to very slow and/or small magnitude changes).  This is not what we are seeing worldwide.”

Anoop | Fri January 13, 2012  

H Viktor,

Didn’t you and Harry read the the subheading in the article in red “If it is genetics, why obesity is on the rise”?

For example, there was a 33% increase in obesity prevalence in the 90’s compared to the 80’s. This sounds huge, but we are talking about a modest 6-8 lb increase in the population!! And this increase is largely from a minority of people who are already heavy (over 30 BMI). What does that tell you, Viktor?

Simon | Fri March 23, 2012  

Hi Anoop,
Could you please tell me the source of picture of twins? What study or article was that picture taken from?

Paul | Fri June 01, 2012  

Hello Anoop. I love this website and I keep reading the articles here, however, this one I’ll need to question.

I am in no way attacking your views, or scientific data that you present, I am simply presenting new data before you so you may consider the odds.

I have read most of your replies on this thread and I believe this is something that hasn’t been brought up. Again, I appreciate all your work, it is great!

Our family was raised in Russia, and in Russia we were all very fit. At around 38 years old my dad moved to the United States, here in the next few years both of my parents gained around 20-30 pounds of fat. However, when we returned back to Russia for a vacation, me, my dad, and my mom all lost around 20 pounds in the two months we were there. Note this: we weren’t hungry/starving, we ate as we wanted. When we returned, all the weight came back in the next year or so.

My conclusion: it is on the environment. The healthier the food, the less obesity. Yes, you did explain the difference between fat and skinny people in the same environment - but I’m talking just about the fat people here - the fat people who have become fat because of their environment.The high amounts of sugar and other tasty ingredients of food and all the harmonically raised foods really do show effect. Our tastebuds love it - and want more, we are naturally eating more not because our body needs more, but because we are psychologically addicted to the taste. If we observe the rise of obesity in America over the past 100 years we will see a trend. Obesity increased by a TON, literally. As you said in the article - genetics can’t change that fast. People with the same exact genetics now live in Europe and aren’t as big. Maybe they got big because of the environment and food they are being served. These are real numbers, consider them.

Right now every single country where fast food is being introduces is increasing in obesity. This should tell us something…

What are your thoughts? I hope you see the bigger picture now.

Guillermo Chussir | Sun June 17, 2012  

“These folks are clearly the minority, around 5-10%. It is not exactly clear how they do it. There might be a subset of people whose conscious motivation can override their biological drive in the long run. Majority of the people can’t.”

I’ve been thinking about this and how it relates with the idea of Ego Depletion. Both ideas make sense with each other, but I wonder if there’s any specific way to avoid or decrease Ego Depletion in the context of dieting. Any ideas?

Anoop | Mon June 18, 2012  

Hi Paul,

Thanks for all the comments. Don’t worry. I love being questioned. Sometimes I am guilty of everything I accuse others of.

I am not saying environment won’t play a role. And I am not saying people won’t gain 15-25 lbs with environment. And I am not saying obesity is not increasing. It is all a matter of degrees you know. And it is just hard to say anything from personal experiences. I go home to India and gain weight. That doesn’t mean in India people are putting on weight. It could be number of other reasons. And even if I put on weight, that doesn’t mean that I will keep on putting on weight or not lose weight.

And when we talk about obesity, we are talking about people who are 50-200 lbs overweight. Maybe I shouldn’t have had that title as the ‘cause’ of obesity.

Hi Guillermo,

No clue what you are saying. Heard about glycogen depletion. Not about ego depletion though.

Anthony | Wed June 26, 2013  

Here is the BBC presentation of some research we discussed previously.


What do you think?



EMAIL *email will never be displayed

URL (optional)

Please answer the question below:

What is the first name of the owner of exercisebiology.com

Remember my personal information

Notify me of follow-up comments?