Muscles do not turn to fat, nor does fat turn into muscle. They are two separate entities and are not interchangeable. Perhaps you have noticed a fat layer on roast beef or pork chops. A similar fat layer occurs with humans. The fat tissue is a layer of fat-filled cells that covers the muscles.
Muscle is the protein-rich tissue that performs exercise.
When you exercise, you build up muscle tissue. When you consume fewer calories than you expend, you reduce the fat layer. If, due to injury or illness, you are unable to exercise your muscles may lose their tone, but they won t turn to fat. Unexercised muscle issue actually shrinks in size. For example, Joe, a skier, broke his leg and was shocked to see how scrawny his calf looked when the cast was removed five weeks later.