When it comes to weight training and gaining muscle, there are plenty of topics which generate debate among lifters in the gym and on the web. Hardly any of those arguments are as heated or passionate as the one surrounding which type of muscle fuel is best for growing big muscles: carbohydrates or fats.
Let’s take a look at both sides of the argument and try to figure out what’s right, or at least closer to right.
The Case for Carbohydrates
Muscle contractions (and other bodily functions for that matter) rely on adenosine triphosphate, or ATP, for immediate energy needs. Your local stores of ATP are exhausted pretty quickly, though, and then your body must turn to stored energy for additional power. While you CAN break down muscle for this purpose, those needed calories will be pulled from fats or carbohydrates most of the time. Those nutrients can come from stored bodyfat, stored glycogen (carbs in the muscle), blood sugar (glucose), or circulating fatty acids.
Most experts agree that when you have both carbs and fat available from digestion, your body will preferentially burn the carbs and store the fat, not the other way around.
What’s more, studies like this one from the University of New Mexico in 1999 show that most of the energy used during endurance training comes from glycogen. A significant portion of the energy required for high-intensity activities, like weight lifting, also comes from glycogen.
The Case for Fats
On the other hand, that same study showed that resistance training yields a roughly equal depletion in the carbs and fatty acids stored in muscles — about 30% each for a bout lasting 30 minutes or so.
This suggests that, while glycogen is important for muscular contractions, it is not the only energy substrate involved.
Proponents of ketogenic diets and other relatively low-carb approaches like Paleo point to these types of results as evidence that the body prefers to burn fat rather than carbs. It’s also true that cardiac muscle — your heart — runs primarily on fat power and that your body does, indeed, shift to burning fats as its primary fuel in the absence of sufficient carbohydrates.
And the Winner Is …
The bottom line is that, while both high-fat and high-carbohydrate diets can provide fuel for intense workouts, most people will do just fine using carbs as their primary muscle fuel.
Now, excessive carbohydrates CAN make you sluggish and cause your blood sugar to yo-yo, particularly if you’re eating a lot of simple carbs with high glycemic indexes. If you focus on fresh fruits and vegetables, whole grains (unless you have an allergy or intolerance), and certain tubers and legumes, however, then you should be able to keep those swings in check and have plenty of energy for training.
Of course, there ARE people who need to keep their carbohydrate levels well-controlled due to health issues like diabetes. As always, you should work with health professionals to come up with the eating plans that fit you best.
In general, though, eat whole, unprocessed foods, get plenty of protein, and include some healthy fats in your diet. This type of simple, balanced approach will keep you feeling good and gaining, and you’ll most likely fall toward the carb-burning end of the energy spectrum.