**Muscle Does Not Turn Into Fat When You Stop Working Out**
A common belief about fitness holds no scientific basis. Muscle and fat cannot convert into each other, says Prof Leigh Breen, a muscle physiology specialist at the University of Leicester.
"There's no known process in the human body that would support muscle turning into fat, or vice versa," Breen states. The confusion arises because people who take breaks from exercise often notice their muscles feel softer or less toned, leading them to believe the tissue itself has transformed.
What actually happens is simpler but involves two separate processes. When you stop working out, you lose muscle mass. At the same time, if your calorie intake and activity levels change, you may gain fat. These occur independently, not as a conversion of one tissue type into another.
Breen notes he hears this misconception frequently from people returning to the gym after extended time away. Their observation that muscles have "softened" reflects real physical changes, but the cause is muscle loss combined with fat gain, not a biochemical transformation between the two tissue types.