Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
10 Aug

How Many Calories Does Muscle Really Burn? (and Why It’s Not About Calories Anyway)

The hallowed halls of the Academy of Broscience contain untold tomes of knowledge, wisdom, and recipes for “sick” pump stacks. Over the years, their scholars have elucidated the arcane esoterica of muscle confusion, thereby making it palatable for the layman. They discovered that any gram of carbohydrate eaten after dusk turns immediately to fat, and that curling in the squat rack engages more muscle fibers than curling elsewhere. Their field researchers are reportedly close to confirming the existence of spot reduction. But perhaps their greatest contribution to modern physical culture has been the establishment of the unassailable fact that muscle burns fifty times more calories than fat, at fifty calories per pound per day. (Even Dr. Oz says it, so it must be true.) As they have so painstakingly shown, adding twenty pounds of muscle increases your resting metabolic rate by 1000 calories. With that kind of leeway, you could eat a delicious twenty egg-white microwaved omelet with low-fat cheese and a side of plain oats and never worry about body fat accumulation!

This, of course, is complete nonsense. Broscience is not even peer-reviewed and their application for accreditation is still in administrative limbo.

No, but seriously: the idea that muscle significantly boosts resting metabolic rate is pretty much nonsense. Now, don’t get me wrong. I like muscle. Love it, even. Nothing I like more than a bit of lean mass, but I don’t like how this notion of “muscle burning fat at rest” has taken hold in the collective psyche. It leads to lofty expectations that come thundering down to shatter to pieces. It gets people on a single, obsessive fitness track where all they want to do is lift, lift, and lift (and eat, eat, eat) some more to the exclusion of other, perhaps more enjoyable pursuits. And, it can even negatively impact one’s health or progress toward desired body composition, either via overtraining the heavy lifting and undertraining the other stuff, like sprints, walks, hikes, and simple play.

Anyway, I came across an article several months ago detailing the author’s discovery that muscles don’t actually burn that many more calories than body fat. He doesn’t cite any specific studies, but he does cite Claude Bouchard, an obesity researcher from the Pennington Biomedical Research Center, who revealed that a pound of muscle, at rest, burns about six calories per day (and a pound of fat burns about two). That’s a far cry from the 50 calories per day figure “cited” by others. This number isn’t available in the abstract of some specific study. It’s drawn from extensive reading of the “biochemical and metabolic literature”. If you have literature to suggest otherwise I’m all ears. For the purposes of this post, though, I’ll take Claude at his word.

So, straight from the guy that studies this stuff for a living, muscle doesn’t burn a significant number of calories at rest. To illustrate the point let me quote the author of the LA Times article:

The 20 pounds of muscle I’ve gained through years of hard work equate to an added 120 calories to my RMR. Not insignificant, but substantially less than 1,000. However, I also engaged in a lot of aerobic activity and dietary restriction to lose 50 pounds of fat, which means I also lost 100 calories per day of RMR. So, post-physical transformation, my net caloric burn is only 20 calories higher per day, earning me one-third of an Oreo cookie. Bummer.

Or a single macadamia nut as the case may be. But that doesn’t mean having more muscle isn’t good for body composition and overall leanness, because it definitely is. Let’s look at some of the metabolic and other benefits of having more muscle mass.

Recent epidemiology (13,644 participating subjects) reveals that skeletal muscle mass strongly correlates with improved insulin sensitivity. With each 10% increase in skeletal muscle index (a measure of how much muscle is on one’s body), HOMA-IR (a measure of insulin resistance) saw a relative reduction of 11%. Folks with higher insulin sensitivity have better glucose control (carbs don’t destroy them) and lower rates of diabetes. Another study looked at the relationship between sarcopenia, or muscle wastage, and insulin resistance. There was a distinct relationship between sarcopenia and insulin resistance, independent of obesity, which can also exacerbate insulin resistance. So, based on epidemiology, a lack of muscle is linked to increased insulin resistance and poor glucose regulation. This should go without saying, but sarcopenia was also linked to obesity.

How does one get increased muscle mass? Why, by lifting heavy things. And what does lifting heavy things do to insulin sensitivity in addition to its effects on muscle mass? It improves it. To show this, a study placed older Hispanic adults with type 2 diabetes on a 16-week resistance training regimen and measured their baseline and post-treatment muscle mass and markers of insulin sensitivity. Folks in the strength training group got stronger, leaner, built more muscle mass, and developed more type 1 and type 2 muscle fibers. They also became more insulin sensitive. The increase in type 1 fibers, in fact, was strongly associated with the improvements in insulin sensitivity, as this graph shows. Note how the sedentary group didn’t do so hot in either department (increasing muscle mass or decreasing insulin resistance). That looks like a pretty strong link between increased muscle mass and insulin sensitivity to me.

Why is this important? Being insulin sensitive means you handle glucose well, which means less dietary glucose becomes body fat and less insulin is required to handle your business. This is far better than the idea of having a rumbling muscular engine idly burning calories as you watch TV, mostly because while the latter is a fun story to tell your bros at the gym, it’s not really true.

Having greater muscle mass also acts as metabolic reserve in times of trauma. I’m not talking about famine or starvation. I’m talking about car accidents, internal damage to organs, severe burns, cancer, sepsis, and catastrophic injury. A great review article (PDF) from five years ago summarizes the role skeletal muscle plays in recovery from and survival of trauma. In these unfortunate but very real instances, protein requirements shoot up to repair damage, and muscle protein breakdown increases. More muscle mass means you have more reserves to keep the amino acids flowing. When healing from burns, dietary protein needs increase to 3 grams per kg of bodyweight. If you can’t stomach that much or dietary protein isn’t available to you, it comes from existing muscle. And, if you don’t have much muscle to spare, you’re going to recover more slowly from severe burns. Same goes for cancer patients; those who have the greatest muscle mass tend to suffer fewer recurrences and live longer. Think of skeletal muscle mass as a buffer for hard times.

Finally, muscle looks good when attached to a human skeleton by tendons and covered with skin. And don’t we all want to look good naked, ultimately? Heck, I’d say this last one is enough reason to lift heavy things by itself.

Now that you’ve (hopefully) ceded the “idle muscle burns fat” idea, we need to go further. Let’s stop thinking of exercise and weight loss in mechanistic terms. Let’s not think of “burning” calories by subjecting our bodies to punishment. Sure, you could grind away and, with enough volume and intensity, “burn” off calories through sheer force of will. If your only concern is that you maintain low body fat, you could eat a bad diet and run fifteen miles a day. I did, and I was skinny. It “works.” But isn’t it much more freeing to realize that 80% of your body comp will come through proper diet, meaning you don’t have to grind on the treadmill and you can instead explore the joy of movement for its own sake? Isn’t it more elegant to imagine the hormonal cascade that heavy lifting jumpstarts and which gently nudges one’s physiology toward leanness and away from adiposity? Whether you see it as science, art, or a blend of both, the way we do things is more effective and enjoyable than hammering away at your fat stores.

Some may continue to hold their peace of mind ransom for those 500 calories of donut they just ate. That’s not me. While they’re waiting for “500 cal” to pop up on the elliptical’s readout, I’ll be eating real food, lifting heavy things, and appreciating the beauty of a complex physiological system allowed to do its thing. I suggest you do the same.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Interesting data showing diabetes suffers being cured through weight training, and that muscular people can recover from severe burn or cancer better. I’d add physical blunt trauma resilience to that list. 4 years ago when I was a soft 185 lb average Joe showing my 2 year old son how to do a forward tumble, it put me in the hospital. These days my idea of fun is getting kicked in the ribs by kickboxers, and taking a 4 foot high fall onto concrete flat on my back did zero damage.

    I do not agree that muscle doesn’t burn vast amounts of calories. It made all the difference for me and many people I know. I got very lean just lifting weights 3 days a week while doing zero cardio while eating a lot more food (including lots of sugar, carbs, fat.

    George wrote on August 23rd, 2011
  2. WOW, great article.

    Antonio wrote on October 19th, 2011
  3. Wait you said that the people who lifted weights “developed more type 1 and type 2 muscle fibers.”

    You meant that the muscle hypertrophied right? We know that muscle cell hyperplasia doesn’t happen in human beings.

    Roger wrote on December 14th, 2011
  4. “When healing from burns, dietary protein needs increase to 3 grams per kg of bodyweight.”
    Do you have a source for this?

    Scott wrote on January 24th, 2012
  5. A lot of people don’t understand how building muscle works. In order to build muscle properly you must first break down the muscle fibers via lifting weights. Second, feed your muscles nutrients like protein and rest the worked muscle for 48-72 hours. It’s like building blocks, knock them down so you can build it bigger.

    John Oxnard wrote on July 9th, 2012
  6. Just wanted to share some thoughts.

    You know that the 60 calories per pound per day for skeletal muscle can’t be correct. If it were, people like me (35% skeletal muscle and 200 lbs, so 70 pounds of muscle, would have a RMR over 4,200 (60*70=4,200).

    I think what happened was that recovering muscle after a heavy work out has a very high calorie per hour burn, probably on the order of a total of 60 calories the first day.

    Another easy way to tell. There is a strict correlation between your heart rate and how much energy you are burning. So you know the “recovery” use of calories is more or less done when your resting heart rate has returned to normal.

    E.g., if i do a really heavy weight workout for an hour, my resting rate over night is 61. If i do hard cardio or nothing special it is 55. Those extra six beats per minute are the increased metabolism from repairing muscle.

    All you have to do is think about these things in a relatively disciplined way and you always get things right.

    If you look at Richard A’s comment, he too has got it right. But again notice he has not (and didn’t need to) say all other things being equal. He also didn’t say that it takes time to build the 5 lbs of muscle and burn off the 15 lbs of fat.

    Bob Mendelson wrote on February 20th, 2013
  7. Ah yes! Went hunting for studies on how many calories muscles burn and was bummed to see you cite the same James Fell article that led me to hunt for studies in the first place … but then saw your follow-up in the comments :)

    Thanks Mark!

    Shane wrote on December 3rd, 2013
  8. The figures are correct. Around 6kC per g skeletal muscle and 2kC per g adipose tissue at rest. I have read the scientific papers.

    Maybe I missed it but I think the author missed a very valid point. Skeletal muscle at rest burns hardly any more calories than adipose tissue true but WORKING muscle burns much more.

    The energy cost of adipose tissue remains fairly constant as apart from an energy store it’s (only!) main other duties are to help regulate hunger through leptin and ghrelin hormones (and some immune system functions and fertility in women) muscle on the other hand when exposed to sufficient overload partially breaks down and needs to be rebuilt.

    This rebuilding involves the breakdown of proteins into amino acids and rebuilding into other proteins, this requires a lot of ATP (energy) so the thermogenic effect of rebuilding muscle increases energy expenditure, this constitutes a large part of what has been termed ‘afterburn’.

    So, whilst a sedentary person with a higher lean body mass will not have a significantly higher BMR than a similar weighted person who has a lower lbm and higher fat percentage, a person with a higher lbm who works out regularly will have a much higher total daily energy expenditure.

    So. Increasing muscle mass CAN help you increase your TDEE significantly but not your BMR by much and only if you use it!

    Yasminsdad wrote on March 13th, 2015

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