Burning fat or burning muscle?
by Jake
(Cincinnati, OH)
So as far as I know the body can use three things for fuel: fat, glycogen, and muscle. It usually uses glycogen, and will use fat when there is no glycogen to use.
But I hear all the time that if you don't get enough protein constantly throughout the day then your body will begin to break down muscle tissue for energy.
This has never made any sense to me, because if your body has a steady supply of carbohydrates then it would never have the need to break down muscle tissue for energy. This also goes for things like distance running and sleeping; your body burns calories/goes without calories for an extended period of time, so it will start to break down muscle tissue for energy even though it has a ready supply of glycogen from either carbohydrates or burning fat.
But other times it's okay to go without protein when exercising, such as right after lifting in order to burn fat and whatnot.
Using the logic from before, though, that would break down muscle tissue for energy. It seems like we have to follow these arbitrarily-imposed guidelines that so-called “experts” tell us in order to belong in the ‘exclusive' club of bodybuilders.
My question is how/why/when does the body decide to burn glycogen/protein/fat for energy, and is it in accordance with what the dogmatic, self-proclaimed internet-gurus tell us we need to do to lose fat/build muscle?
Bill's take: Ah, the Billion Dollar Question!
In short, it's hard to say. Or, put another way, “It depends.”
I know, not very concrete. Here's my view: The body hoards fat. This much we know. If faced with the specter of starvation, the body will use any other available source of fuel, including muscle, over fat, in order to keep vital organs functioning. This is a product of thousands of years of survival.
I will say that the body also will use only whatever protein it needs. Get “enough” in your diet and you won't lose muscle tissue. But take in too much and your body converts the protein to fat.
Let's take this to the extreme, on both sides.
Too little protein: Since our muscles are constantly being broken down, if we eat NO PROTEIN, our muscles will shrink.
Too much protein: It gets converted to fat.
In fact, too much of anything gets turned into fat.
So there's a fine line between too little and too much. We in the bodybuilding world want insurance and since we're trying to build muscle, we take too much, knowing that if we watch our body fat levels, we can adjust.
So you really can work out very hard and shrink if you don't eat enough protein.
The discussion becomes more complicated when talking about when the body uses glycogen versus muscle versus fat.
Too little carb, too few overall calories, the body goes into starvation mode and will “eat” the muscle. Low carb, but not zero, and good protein and fat intake, the body, if you exercise, will burn fat.
Same goes for too little fat and too few overall calories, but the results may be even more harmful.
The body can — and does — convert protein into fuel if it needs to. It's just really expensive!
This is why low carb/high protein diets (with exercise) works for fat-burning.
There's a good article about this dietary balancing act here.
Here's a fantastic article about high protein diets.
All in all, if you eat a relatively balanced diet (50/30/20 or 60/20/20 carbs/protein/fat) and exercise (both strength-training and cardio), you will burn equal levels of fat and carb calories.
However, if you eat too much (more than maintenance at your given activity level), you will get fatter. Eat just a little less than maintenance level and you'll lose fat.
I hope this helps!
