Fat and muscle are two different types of tissue; It is physiologically impossible for a tissue to be converted into another type of tissue. Fat cells are called adipose tissue. This tissue will store fats from the diet if the fats being consumed are not needed as an energy source. Thus, the fat cells increase in size. Your body makes fat from excess food not just fat in the body. It is important to note, it’s not only dietary fat that becomes body fat: Extra nutrients of any kind has the potential to become “new” fat through a complex process called fat synthesis. According to Dr. John Berardi of Precision Nutrition, fat synthesis typically occurs with a high sugar diet versus a fatty diet.