Have you ever heard fitness pros and mainstream media claim that this or that exercise program will turn your fat into muscle? Well, we regret to inform you this claim — as good as it sounds — is simply false.
The process of burning fat is completely separate from the process of building muscle, though the two processes are related to each other, says Lauren Shroyer, MS, director of product development for the American Council on Exercise (ACE). “The phrase of turning your fat into muscle likely came from that relationship, and was a huge oversimplification of the process that actually happens,” she adds
To help clarify the relationship — and how you can use it to your advantage — we explain the process of building muscle and burning fat in more detail.
HOW YOU BUILD MUSCLE
To build muscle, you first have to break your muscles down. The best way to do this is to place more stress on your muscles than they’re accustomed to.
“Your body is adapting to any of the stresses that you put upon it, so if you are exercising and you are increasing the amount of weight you lift or the distance you run, you are providing an environment for your muscles to become stronger in one way or another,” Shroyer says.
More specifically, when you lift weights or otherwise stress your body, you cause damage to your muscle fibers. Once damaged, your muscle sends out an SOS signal for unique cells known as satellite cells to come to rescue and repair or replace those damaged fibers. When paired with the right amount of each macronutrient (i.e., protein, carbs and fat), you can ultimately build muscle mass.
What’s more, your damaged muscles are especially receptive to the recovery-boosting effects of protein and glycogen (carbs your muscles use for energy) immediately after your strength or exercise session, which can help you build new muscle — so long as you refuel properly.
HOW YOU BURN FAT
Burning fat, on the other hand, is a matter of creating a calorie deficit: “When your body is in a situation where you’re using more calories for energy than you’re taking in through food, then it has to turn to other forms of stored energy to fuel life’s activities,” Shroyer says. Often — though not always — this means burning fat for fuel.
You can achieve a calorie deficit in a few different ways:
Cut calories from your daily diet. (Experts typically recommend cutting no more than 500 calories per day.)
Burn calories via exercise while keeping your daily caloric intake the same.
Eat slightly fewer calories per day and burn a small amount via exercise. (Example: Cut 250 calories from your diet and burn 250 calories during your exercise session.)
HOW TO BURN MORE FAT
Doing a combination of diet and exercise will likely be your best option for burning fat. Exercise in general — and strength training in particular — offers plenty of benefits, both in terms of overall health and burning fat. “It’s really the simultaneous shifts of healthy eating habits and increasing activity that will get quick results,” Shroyer says.
Granted, you probably won’t burn a ton of fat during exercise unless you’re doing something low-intensity (Think: an easy jog, walk or bike ride). Strength training and moderate-to-high-intensity forms of exercise (Think: moderate-intensity cardio and HIIT) tend to burn more glycogen (the storage form of carbs) than fat.
However, increasing muscle mass via strength training is a great way to boost your daily calorie burn. Unlike fat, muscle is a metabolically active tissue, which means it burns calories, even at rest. As you add more muscle to your body, you’ll raise your basal metabolic rate, or the number of calories your body burns in a resting state.
Low-intensity, fat-burning exercise isn’t necessarily the best way to burn fat. Sure, you’ll burn a greater proportion of calories from fat (approximately 60%) when you work at a lower intensity, but higher-intensity exercise usually burns more calories overall (though it may depend on the length of your workout). If you burn more calories overall during moderate- and high-intensity exercise, you could wind up burning more calories from fat.
Here’s an example from the American Council on Exercise: Assume you burned 200 calories during a 30-minute, low-intensity workout; roughly 120 of those calories came from fat. Now assume you burned 400 calories from a 30-minute HIIT workout; roughly 140 of those calories (35%) came from fat. Not only did you burn twice as many calories during HIIT, but you also burned slightly more calories from fat in the same amount of time.