No. Muscle and fat are two different types of tissues. Muscle can never become fat or vice versa. The components the body uses in order to make fat or muscle are not the same, so while it can appear that one might be transforming into the other, it is not physically possible.
So, what’s actually happening when we see these dramatic changes in our body composition over a period of time?
The prime factor in how much or how little fat you have in your diet. The determining factor in the amount of muscle you have is your exercise regimen.
Fat is made of thousands of cells that have the ability to hold onto fluid. Fat cells respond to conditions in the body in three ways: they shrink when there is less food energy available, they stay the same when there are adequate calories, and they grow if there is an excess in caloric intake.
Food energy does not have to begin as fat in order to be stored as fat. Your body has to break everything you eat into pieces small enough to get into the individual cells, which means carbohydrates go through multiple processes in order to become glucose, protein gets broken into amino acids and fat will wind up as fatty acids. Your body does not typically lose fat cells unless you surgically remove them and will not usually make more individual cells past a certain age during puberty, although if you gain a tremendous amount of weight as an adult, your body will adapt by letting the cells divide.
Hundreds of muscle fibres work together to form each muscle cell in our body. Each individual fibre is capable of getting bigger and of packing more material into the same space. Muscle cells also become more efficient through improved coordination in the body beyond its “comfort zone”. Muscles grow bigger by experiencing stress: only the muscles being stressed can undergo these modifications. This means that muscle building can be location-specific, whereas fat storage and loss are not.
While your body will not physically transform fat to muscle or even let muscle become fat, your choices and habits dictate how much fat or muscle your body maintains. So, make good choices in your diet and exercise programs and you’ll be able to keep more muscle and shrink those fat cells!