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Which Equation to Calculate My Daily Maintenance Calories?

June 21 2008

Understanding how to find daily maintenance calories and Resting Metabolic Rate (RMR/BMR) is vital if you are trying to lose weight. After reading the whole article, you will have a better understanding of calculating daily maintenance calories (and RMR) and the issues revolving around it.

What are maintenance calories?

Maintenance calories are the number of total calories you burn during a day or your daily caloric requirement. 

As shown in the pie chart 1, It can be broken down to three pieces:
Daily Caloric Expenditure= Resting Metabolic rate (RMR) + Thermogenic effect of food + Activity thermogenisis

image

As shown below in pie chart 2, activity thermogenisis can be further divided into two: Exercise activity thermogenisis + Nonexercise activity thermogenisis.

image

Why is calculating RMR so important?

From the first pie chart it is pretty clear that Resting Metabloic Rate (RMR) forms a big chunk of your daily maintenance calories (60 -70%). If that’s clear, then the importance of accurately calculating RMR to find your maintenance calories becomes easily clear.

Why is measuring or estimating RMR a problem?

RMR or Resting Metabolic Rate is the number of calories you burn to maintain your vital functions such as breathing, pumping blood, maintaining muscle and nervous system at resting conditions.

Measuring RMR:Measuring RMR accurately requires the use of an apparatus called indirect calorimetry. It’s not just you, but most can’t afford that expensive piece of equipment.  So forget about the measurement option of RMR.

Estimating RMR:The second and our last option is to estimate RMR. Fortunately, different equations have been developed to estimate or predict your RMR. Unfortunately, there are problems associated with each of them.

  • Equation Errors: As is the case for any estimation or prediction equation, it comes with a load of errors.
  • Number of equations: Over 138 different equations have been developed by over 40 different authors to estimate or predict RMR.
  • Population specific: Population specific means these equations will only stay valid if they are applied to populations for whom these equations were developed in the first place. So an equation developed for obese will give large errors if used on a normal healthy individual. Or an equation developed for younger folks for RMR can result in different numbers for an older person.

So which RMR equation should I use?

Normal healthy individuals:Harris-Benedict equation was the first equation to be developed and still is used widely for normal healthy individuals, even in clinical settings. I must add that though it reads BMR (instead of RMR), the measurement conditions were for RMR and hence it is technically RMR.

Harris Benedict formula

Table 1.Harris-Benedict equation

Overweight & Obese Individuals:

Mifflin / Bernstein/Robertson & Reid equations

Mifflin is also used for normal individuals and sometimes believed to better than Harris - Benedict (established in 1919) since it is relatively recent and hence it represents our current life style. That been said, there is no single best one as each has shown to better than the other in different studies. So pick the name you like the most.

Mifflin equation for calculating maintenance calories

Table 2. Mifflin’s equation

Athletes & active individuals

Cunningham equation

Studies have shown fat-free mass to account for almost 80% of the variation seen in RMR. So it makes a lot of sense to calculate RMR based on fat free mass (FFM). And guess what, Cunningham uses FFM as the predictor variable to estimate RMR. Cunningham used the data from the Harris-Benedict study to formulate the equation.

Cunningham equation for calculating maintenance calories

Table 3. Cunningham’s equation

Though both used non athletes in the Cunnigham study, considering the life styles in those days the participants (year1919) could easily represent active individuals. This was kind of confirmed by a study done on endurance athletes (active individuals): In the study, only Cunningham, predictions (followed by Harris-Benedict equation) fell within the accepted range.

However, again I remind that these equations are population specific. And a specific equation to calculate RMR for weight lifters or bodybuilders (greater FFM and less fat mass) is yet to be formulated. 

NOTE: Lest you forget, along with RMR, you have to calculate the thermic effect of food and activty thermogenesis to get your Total Caloric intake.

Conclusion

I hope now it is clear that there is no single best equation to estimate Resting Metabolic Rate or RMR. For most, the Harris Benedict or Mifflin would work just fine. If you know your body fat percentage and if you are quite active, Cunningham should be your first choice to find your RMR.

Reference 1
Reference 2

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Sundar | Sun August 03, 2008  

Anoop dude, this is Sundar from SIUE. Your website is awesome man. I love it.

Great work dude, very helpful. Call me at 618-334-6141.

Take Care,
Sundar.

Anoop | Sun August 03, 2008  

Thanks bro for chiming in!! Hope you are doing good.

True Blood | Fri April 16, 2010  

Great article. I really like it. Thanks for information a lot.

Ali | Thu May 27, 2010  

My maintenance is 8250 kJ (or 1969 calories). How much extra calories do you think is adequate for muscle gain with minimal fat gain?

An extra 300-400 calories?

Forum | Thu May 27, 2010  

Thank you

martin | Wed June 02, 2010  

Great article. I really like it. Thanks for information a lots. My Gizlesene site.

Andy Walsh | Sat June 05, 2010  

There’s also the Katch McArdle formula which Tom Venuto, Author of “Burn the Fat, Feed the Muscle” talks about in that book and presumably uses.

When I got my personal trainer qualification, my teacher (who trained Charles Clairemont among other decent athletes), taught us the Cunningham method.

Both methods differ by a good 10% total expenditure. Very hard to know which to use. It’s all esitmations.

I say to use any of these figures (bodyfat %, lean mass, daily expenditure) as something to aim at so you’re in that ballpark.  Then adjust from there.

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