Do Your Muscles Actually Turn To Fat If You Stop Training?

When you start exercising and weight training, your body slowly builds muscle mass. While this won't suddenly happen overnight, you can gradually help strengthen your muscles and increase your muscle mass in just a matter of weeks. But what happens when you stop training altogether? Although it's commonly said that muscle turns into fat when you stop exercising and adopt a more sedentary lifestyle, that's not exactly the case. That's because turning muscle into fat is physically impossible. According to Piedmont, fat and muscle tissue have completely different cellular makeups.

"Fat cells and muscle cells are different structures and are not interchangeable. It would be like an orange turning into an apple. It's not possible," Hahns Petty, an exercise physiologist, told Piedmont. "A lot of people feel and look less tight and toned when they stop working out. It's more of a cosmetic thing." So, if that's the case, why does your body appear less toned when you're not working out regularly?

As it turns out, your body loses muscle mass when you stop exercising and weight training regularly. If you're used to a fairly active lifestyle, becoming more sedentary can reduce the size and strength of your muscles, according to Livestrong. That's because inactivity causes blood flow to be directed away from your muscles. Without this fuel, your muscles will start to shrink and decrease in mass. Surprisingly, this doesn't take as long as it does to build strength and muscle mass in the first place.

"Strength goes down almost immediately," Dr. Michael R. Deschenes, professor of kinesiology and chair of Kinesiology and Health Sciences at The College of William & Mary, told Eat This, Not That. In just one week, men can lose up to 16% of their strength, while women can lose as much as 29%. However, after three weeks of inactivity, both men and women will start to lose muscle mass.