Myth.
Muscle tissue does not turn into fat when you stop exercising. Instead, when you stop exercising, your muscle mass can decrease due to atrophy, while fat mass may increase if you consume more calories than you burn. Muscles and fat are different types of tissue, and one cannot convert into the other. However, a decrease in physical activity can lead to a decrease in muscle mass and an increase in body fat over time if lifestyle factors such as diet are not managed.