How Many Calories does Muscle Really Burn?

Posted: May 21, 2014 in Lifestyle, Nutrition, Training
Tags: , , , ,

The metabolic effect of adding muscle is misunderstood and greatly overstated. Most fitness professionals will tell you that each pound of muscle burns an extra 40-50 calories per day, which is just not true. The real number is about 6 calories. So you put on 10 pounds of muscle, and you’re buring an extra 60 calories a day…who cares? Thats a couple bites of a meal.

Fat cells are misunderstood as well, most people think of them as inert, but they actually burn about 2 calories per pound/per day by producing adipokines and various other tasks. So muscle is only 3x more metabolically active than fat. Not a huge difference. And if you lose 10lbs of fat, and replace it with 10lbs of muscle, that increase of 60 calories now drops to 40 extra calories burned per day due to the metabolic decline from the loss of fat cells.

That doesn’t mean that adding muscle won’t help you get lean faster, it just does so through a different mechanism than calorie burning, which, among other things, is improved nutrient partitioning. So when you eat, you’re basically giving your food Google Maps directions to your lean tissue, and away from fat tissue. As I’m sure many of you know, this is actually one of the ways steroids work their magic. There are numerous other ways adding muscle helps speed up fat loss, but that’s not what this post is about.

A recent study looked at all of the previous data on this subject, but with new testing methods. This research published in The American Journal of Clinical Nutrition affirmed the previous data regarding calories burned by various tissues and organs, summarized below, listed in calories burned per pound/per day (the study used kilograms, I’ve converted to pounds).

This study shows, for the first time to my knowledge, that calories burned are over-estimated in people over the age of 50. Although statistically significant, the numbers aren’t really worth fussing over in reality as the differences are quite small.

Daily calories burned per pound of tissue

Liver 90
Brain 110
Heart 200
Kidneys 200
Skeletal Muscle 6
Adipose Tissue (Fat) 2
Everything else (spleen, bone, adrenals, etc) 5

Here’s the new study:

Am J Clin Nutr. 2010 Oct 20.

Specific metabolic rates of major organs and tissues across adulthood: evaluation by mechanistic model of resting energy expenditure.

Wang Z, Ying Z, Bosy-Westphal A, Zhang J, Schautz B, Later W, Heymsfield SB, Müller MJ.

BACKGROUND: The specific resting metabolic rates (K(i); in kcal · kg(-1) · d(-1)) of major organs and tissues in adults were suggested by Elia (in . New York, NY: Raven Press, 1992) to be as follows: 200 for liver, 240 for brain, 440 for heart and kidneys, 13 for skeletal muscle, 4.5 for adipose tissue, and 12 for residual organs and tissues. However, Elia’s K(i) values have never been fully evaluated.

OBJECTIVES: The objectives of the present study were to evaluate the applicability of Elia’s K(i) values across adulthood and to explore the potential influence of age on the K(i) values.

DESIGN: A new approach was developed to evaluate the K(i) values of major organs and tissues on the basis of a mechanistic model: REE = Σ(K(i) × T(i)), where REE is whole-body resting energy expenditure measured by indirect calorimetry, and T(i) is the mass of individual organs and tissues measured by magnetic resonance imaging. With measured REE and T(i), marginal 95% CIs for K(i) values were calculated by stepwise univariate regression analysis. An existing database of nonobese, healthy adults [n = 131; body mass index (BMI; in kg/m(2)) 50 y (n = 37).

RESULTS: Elia’s K(i) values were within the range of 95% CIs in the young and middle-age groups. However, Elia’s K(i) values were outside the right boundaries of 95% CIs in the >50-y group, which indicated that Elia’s study overestimated K(i) values by 3% in this group. Age-adjusted K(i) values for adults aged >50 y were 194 for liver, 233 for brain, 426 for heart and kidneys, 12.6 for skeletal muscle, 4.4 for adipose tissue, and 11.6 for residuals.

CONCLUSION: The general applicability of Elia’s K(i) values was validated across adulthood, although age adjustment is appropriate for specific applications.

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For those interested, here’s a paper published 10 years ago discussing all of this, including Elia’s values from 1992. See Table 3 on E451 for the breakdown.

Click to download: Calories Oxidised per day by tissues and organs

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Comments
  1. […] The metabolic effect of adding muscle is misunderstood and greatly overstated. Most fitness professionals will tell you that each pound of muscle burns an extra 40-50 calories per day, which is just not true. The real number is about 6 calories. So you put on 10 pounds of muscle, and you're buring an extra 60 calories a day…who cares? Thats a couple bites of a meal. Fat cells are misunderstood as well, most people think of them as inert, but th … Read More […]

  2. John Stone says:

    When you say that muscle burns only 6 extra calories a day that is a muscle at rest, correct? So 45 minutes of high intensity training would affect those values. And perhaps a long day of hiking or touring through europe would make those otherwise lame fat-burning machines a little more significant? Still though it’s a far cry from the 50-100 calories mentioned by people wanting to sell their workout programs.

  3. Yes this is the resting energy expenditure of the tissues discussed. Calories burned during activity is a whole ‘nother story, and one I should probably write a blog about. Some of the traditional methods of measuring caloric expenditure of weight training are fairly flawed.

  4. Elena says:

    Am J Physiol Endocrinol Metab. 2002 Jan;282(1):E132-8.
    Body-size dependence of resting energy expenditure can be attributed to nonenergetic homogeneity of fat-free mass.

    Heymsfield SB, Gallagher D, Kotler DP, Wang Z, Allison DB, Heshka S.

    New York Obesity Research Center, St. Luke’s-Roosevelt Hospital, New York, NY 10025, USA. SBH2@Columbia.edu
    Abstract

    An enduring enigma is why the ratio of resting energy expenditure (REE) to metabolically active tissue mass, expressed as the REE/fat-free mass (FFM) ratio, is greater in magnitude in subjects with a small FFM than it is in subjects with a large FFM. This study tested the hypothesis that a higher REE/FFM ratio in subjects with a small body mass and FFM can be explained by a larger proportion of FFM as high-metabolic-rate tissues compared with that observed in heavier subjects. REE was measured by indirect calorimetry, FFM by dual-energy X-ray absorptiometry (DEXA), and tissue/organ contributions to FFM by whole body magnetic resonance imaging (MRI) in healthy adults.

    Four tissue heat-producing contributions to FFM were evaluated, low-metabolic-rate fat-free adipose tissue (18.8 kJ/kg), skeletal muscle (54.4 kJ/kg), and bone (9.6 kJ/kg); and high-metabolic-rate residual mass (225.9 kJ/kg)….

    Note that each kg is roughly 2 pounds, and each calorie is 4kj

    Note than each kg is roughly 2 pounds, and each calorie is 4kj.

    So, muscle does burn 14cal/kg or

  5. […] Once your calories have been redirected the two most important ways to continue to shed body fat and weight are nutrition and activity. Eating a low calorie, healthy and nutritious diet will provide your body with the proper fuel and increasing your bodies metabolic cost during exercise helps shovel those calories on the fire instead of allowing them to land in storage. “The metabolic effect of adding muscle is misunderstood and greatly overstated. Most fitness professionals will tell you that each pound of muscle burns an extra 40-50 calories per day, which is just not true. The real number is about 6 calories. So you put on 10 pounds of muscle, and you’re buring an extra 60 calories a day…who cares? Thats a couple bites of a meal. Fat cells are misunderstood as well, most people think of them as inert, but th …” Read More […]

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