How many calories does muscle tissue really burn?
It has become widely known that the more muscle tissue you have, the easier it will be for you to keep your weight (body fat levels) where you want it to be. The reason behind this is that your muscle tissue is constantly burning calories (even at rest or while you are asleep), while your body fat tissue just "sits" there (doing nothing except spoiling your looks). A common belief has formed that each additional pound (0.45 kilograms) of muscle mass means you will be burning 50 extra calories per day. If you hit the gym real hard and put on 10 pounds (4.5 kilograms) of muscle, you could be burning an additional 500 calories on a daily basis. If you ever make it to 20 pounds (9 kilograms) of muscle, you will be burning an additional 1,000 calories every single day (before actually even doing anything with all that muscle). Let's not rush out to get a gym membership just yet. First, I will take a closer look at whether or not these numbers are actual facts or just another example of bro-scientific guesstimates (which would definitely be a first in the entire weight loss industry).
Which body tissue burns the most calories?
According to this study, some of the relevant calorie-burning furnaces in our bodies are:
- our internal organs (brain, liver, heart and kidneys) together account for almost 60% of our resting energy expenditure (the calories we burn even without actually doing anything)
- muscle tissue is responsible for about 22% of calories we burn during rest
- body fat tissue contributes only around 4% to the resting energy expenditure
From this, we can already clarify one thing. Our body fat tissue does not just "sit" there, but it actually does help to burn some calories. While 4% is not something to write home about, I didn't want to leave you with the impressions that your body fat stores are a COMPLETELY evil thing. Another hot topic in the weight loss industry right now is the metabolically active (calorie-burning) form of body fat tissue, the so-called brown adipose tissue, but this is a story for another (colder) day.
How many calories does a pound of muscle burn?
The next thing we need to estimate is how much calories muscle tissue can actually burn. The fact that it only contributes to around 22 percent to our resting metabolic rate was an immediate red flag for the commonly known burn rate of 50 calories for each pound of muscle tissue. Let's do a simple calculation on an example resting metabolic rate of 1,700 calories (a number close to the rates actually measured in the study). This means that the muscle tissue accounted for only about 350-400 calories of the 1,700 calories burned. According to the measurements of the study, participants had approximately 63 pounds (29 kilograms) of muscle tissue on average. This means that each pound of muscle contributed about 6 calories (each kilogram of muscle provided about 13 additional calories per day) to daily resting energy expenditure, which is far from the promised 50 additional calories.
The myth that gaining a pound of muscle tissue can lead to a 50-calorie increase of our calorie burn rate was completely busted by science. While muscle tissue will actually contribute more to the calorie-burn rate than your body fat tissue, you can only expect a relatively small boost. Don't get me wrong, I am not against putting on more muscle mass since there are plenty of other reasons why walking around with more muscle tissue beats being stuck with excessive body fat. But as far as calorie balance is concerned, you will probably be much better off relying on the good old diet & exercise combo than on your muscles.