Can muscle turn into fat?

“If you stop exercising, your muscles will turn to fat!” This is commonly heard everywhere from gyms to late-night infomercials. It may be considered a figure of speech on one level, but in fact many people seem to believe that this is an accurate description.

If your activity level decreases, and especially if your calorie consumption increases, you will see your muscles slowly shrink away and be seemingly replaced with fat. Although your muscle cells are shrinking with disuse and your fat cells are growing larger to store the extra calories, you still have the same number of muscle cells and fat cells as before.

The human body is comprised of hundreds of different types of cells, each with their own distinct purpose. There are cells in the eye that are photoreceptive, cells on your tongue that detect taste, and cells in your brain that process thoughts. But, one type of cell cannot turn into another.

Muscle and fat cells are often grouped together but are in fact very different; muscle cells, known as myocytes, are long and fibrous while fat cells, known as adipocytes and lipocytes, are globular.

While some will welcome the news that muscle cells cannot turn into fat, there is one unpleasant additional fact: if fat cells reach their maximum capacity – they just make more fat cells.