FALSE: This is just a common figure of speech that we have adopted when it comes to working out or losing weight. Muscle and fat are two completely different types of tissue. One cannot “turn into” another. When you stop weight training for a period of time, you may begin to lose muscle mass and the muscle tissue degenerates to be metabolized for energy. Your metabolism also may begin to slow down from lack of exercise which may cause a increase in fat gain.
VICE VERSA: You cannot turn fat into muscle. Through a series of periodized aerobic and anaerobic exercise, you will start metabolizing fat which leads to decreased body fat. And at the same time you are increasing your muscle mass. The more you workout the more muscle you will get. The more muscle you have, the more calories your body needs to burn to support your new muscle tissue. And the more calories you burn, the more fat you burn! But at no point in time does muscle “turn into” fat, or fat into muscle. It’s just a figure of speech.