MUSCLES DON'T TURN INTO FAT IF YOU DON'T USE THEM

From THE WISE GEEK

MUSCLES DON'T TURN INTO FAT IF YOU DON'T USE THEM

Despite the popular misconception, muscles won't actually turn into fat if you don't use them. The reason for this common misconception is likely, because as you stop using muscles, they get smaller. At the same time, if you keep eating the same amount of food, you'll usually gain fat since you decreased your energy output. The new fat often appears in the space provided by the shrinking muscles, leading to the appearance of muscles turning into fat.