Sometimes things get repeated enough times by enough people that they are simply assumed to be true.
For instance, how many of you ever had your mother tell you not to go swimming for an hour after you eat? Why do mothers everywhere tell their kids this? Who the hell knows?
But it's been repeated so often that people just blindly accept that if you don't wait 60 minutes after eating before jumping in the pool, you'll be overcome with cramps, flail around for a while, and drown. This will of course happen while your mother stands by, wagging a finger in your general direction, and with a stern tone stating that she told you so, and by the way you better have clean underwear on young man.
I'm calling bullshit on that.
Next time you go swimming, bring a sandwich IN the pool with you and eat it. Let me know if you drown. I'm betting you don't.
Another thing I'm calling bullshit on is the oft-repeated claim that a pound of muscle burns 50 calories per day, even at rest.
In the past two days I've not only seen two fitness pros (who should know better) parroting this, but I did a quick search and found this figure in articles all over the internet. Truth be told, I've probably been guilty of saying it at some point in the past. Probably even followed that up with a quote about waiting an hour before going for a swim.
But, the reality is that this is bullshit. I know some of you out there are already looking up some study that purportedly backs up the claim.
Don't waste your time. Instead, just do some simple math.
An average 200 pound male is made up of about 42% muscle(1). 200 x .42 = 84 pounds of muscle. 84 lbs x 50 cals = 4200 calories burned by muscle mass, every day.
Bullshit. Plain and simple.
The number of calories you burn in a day before factoring in your activity level is your resting metabolic rate, or RMR. There is an equation used to determine the resting metabolic rate of a person called the Cunningham Equation(2). The basic equation is
RMR = 500 + 22(fat free mass in kg)
So, let's say our 200 lb male has 18% bodyfat. That would mean his fat free mass is 200 x .82 = 164 lbs. (remember, fat free mass includes muscle, bones, organs, blood, water, etc.)
164lbs is roughly 75kg, so his RMR = 500 + 22(75) = 2150 calories per day. That includes calories burned not only by muscle, but metabolic processes and organs, which actually makes up a larger percentage of RMR than muscle does.
So, obviously, this guy's 84lbs of muscle mass isn't burning anywhere near 4200 calories per day at rest.
In fact, skeletal muscle only accounts for about 20% - 25% of your RMR, far less than your organs and metabolic processes(3). At 25%, in our theoretical 200lb guy, that would be 2150 cals x .25 = 538 calories burned by skeletal muscle. That works out to a little less than 6.5 calories per pound of skeletal muscle. That's not quite 50 where I come from.
So why the hell do people keep saying that adding a pound of muscle increases your metabolic rate by 50 calories per day? Most likely because they are just parroting what they heard someone else say, they believe everything they read, or they're just too lazy to actually do some math to see if what they're saying makes any f'g sense.
It's probably a combination of the three.
Now, I know that this number is probably a big disappointment to a lot of you. After all, it's commonly preached (yes, that includes by me) that resistance training (the type of exercise that builds muscle) is an important component of a comprehensive exercise program. But if another pound of muscle is only going to burn 6 or 7 calories per day, and it's so hard to pack on muscle, why the hell is it worth it?
Well, you need to look at the bigger picture.
The goal of adding muscle isn't simply to burn more calories at rest, though that is a nice benefit. More muscle on your body, even if your weight doesn't go down, means you're carrying less fat. Muscle is what gives your body an appealing shape. Being strong is a good thing. The more muscle you have as you age, the better off you will be. Who wants to be a tired, weak, frail 65 year old? Plus, if you have more muscle, you can work harder when you exercise, thus burning more calories.
So, while the 50 calories per day number is bullsh*t, you still want to have more muscle and less fat. Forget the numbers and just focus on eating right and exercising regularly, and yes, keep including resistance training in your program.
So, what do you think? Disappointed in the numbers? Upset that you've been misled? Think my math is bullshit? Have some better math to share? Feel free to add to the discussion in the comments.
(1) Marieb, Elaine; Katja Hoehn (2007). Human Anatomy & Physiology (7th ed.). Pearson Benjamin Cummings. p. 317.
(2) Cunningham, J.J. Body Composition and Resting Metabolic Rate: The Myth of Feminine Metabolism. Am. J. Clin. Nutr. 36:721 1982.
(3) Exercise Physiology. McArdle, William D. 2nd edition. 1986. Lea & Febigier, Philadelphia.