There are hundreds (probably thousands) of diet/weight loss websites that make the claim “muscle burns more calories than fat” (google) I’m curious whether this is actually true, and if it is, exactly how much more?
Since the statement as googled is a bit ambiguous, I’ll clarify. I consider the assertion to be “1 pound of muscle, at rest, burns more calories in a 1 day period than a pound of fat in the same person”.
Various searches on various health sites and google have revealed varying specific claims, from “30 to 50 calories a day” to “3000 percent more”.
Mithochondria, the workhorses of firing up the furnaces…live in muscle.
They eventually produce the enzymes needed to reduce glucose to pyruvate and pyruvate to lactate. Getting glucose burned is a good thing.
Muscles are essentially engines…powerplants with a fuel demand. Fuel demands that go down with activity, but any demand is better than none (fat being passive).
Authoritative source? Good luck, but if you can start to understand there are things cooking in the muscles around the clock, you can see that all that cooking requires calories to sustain it (so calories are being burned and won’t contribute tonfat later…or those very cals could come from the fat reserves). Whwile Fat requires calories to be moved, at rest it contributes virtually nothing to a metabolism.
AFAIK, the only calories that fat burns are the extra calories muscles have to burn in order to lug the fat around. I didn’t know that fat burns any calories at all.
I couldn’t find a good authoritative source online, either, but I did find a Web site (The British United Provident Association - www.bupa.co.uk) that provided references to print articles at the bottom of this page on their Web site: Changing your relationship with exercise and activity. They referenced the following publication to support their statement that muscle burns more calories than fat:
Food Standards Agency. Manual of Nutrition (10th Ed) 1995. Page 24. The Stationery Office, Norwich.
Hope that helps. It is true that muscle burns far more calories per pound than fat does, but few people can decide exactly how many more calories muscle burns. Some say 30-50 per pound per day while others say 100 per pound per day. Either way, most people agree that it takes 3,500 calories to burn one pound of fat and it’s better to have more lean tissue than fat.
I can’t give an authoritative answer, and my knowledge of anatomy/physiology is about the same as Philster’s so i can’t add onto it.
However i do know many people who lift weights and use muscle building drugs, and they really muscular ones (those in the 250-300lb range) tend to eat about 5500 calories a day and still be thin. The semi muscular ones eat around 4500 calories a day. None of the people i know who weight 250-300 lbs of fat come anywhere near eating 6000 calories a day.
Huh, I’ve always accepted this as fact but it’s surprising hard to find stuff supporting it.
I did find this article which midway down under “resistance exercise” discusses this issue.
This seems awful vague to me as well. How much lean body mass produces the effect?
Interestingly, none of the formulas I can find for calculating basal metabolic rate take body composition into account although most sites caution that a person who has more muscle burns more calories.
Anyway, maybe one of the medical dopers will come along with some cites…
Let me clarify my previous post and avoid some typos.
Moving fat: It takes energy to literally move fat. To move ones body through the world.
It also takes energy to move fat reserves.
But the fat ain’t do nothing except being a burden or a resource. And when at rest, it is doing nothing. Meanwhile, back in the muscles, mitochondria are busy supporting the whole muscle…and if there is more muscle, there is more to support. Support = metabolism…cals being burned.
At rest, muscle is working to sustain itself and metabolize other bits.
At work, muscle is really working. If energy is depleted, fat resources are tapped. Energy will be depleted a lot sooner with a lot of muscle mass, speeding up the rate at which muscles become dependent on fat reserves to be tapped.
Fat cells are alive, and as such do need to burn a bit of energy to carry on whatever processes that they do, like making the proteins that handle uptake/burning of fats, disposing of random junk that builds up, stuff like that. This does require energy, but very very little. Your average muscle cell is much busier, working just to maintain normal muscle tone even as you sleep (which requires using energy-storing molecules to get other proteins to pull against each other, keeping everything tight), plus keeping up readily available short-term energy stores so that you can move whenever the notion hits you, instead of having to go to the liver, breaking down some stored glycogen into glucose, shipping it over to the muscles, and burning that, which is much too slow.
Since the main purpose of fat is to store energy, you wouldn’t want to waste a lot of energy doing it. Most energy is produced by converting sugars into other acids and then into oxygen and energy (search the web for glycolosis, Kreb’s cycle or oxidative phosphorylation). This is done in mitochondria, found much more frequently in muscle than fat.
How much more frquently? I’m not sure. I lent my histology book to my sister. A lot, though. The claim is certainly true.