Fat cells never go away once you get more of them. That’s why it’s so easy to gain weight for people who have been overweight before!
When you “lose” body fat, the fat cell (also called an adipocyte) does not go anywhere or “move into the muscle cell to be burned. The fat cell itself, (unfortunately) stays right where it was – under the skin in your thighs, stomach, hips, arms, etc., and on top of the muscles – which is why you can’t see muscle “definition” when your body fat is high.
It was once believed that the number of fat cells could not increase after adulthood, only the size of the fat cells could increase (or decrease). We now know that fat cells can indeed increase both in size (hypertrophy) and in number (hyperplasia) and that they are more likely to increase in number at certain times and under certain circumstances, such as 1) during late childhood and early puberty, 2) During pregnancy, and 3) During adulthood when extreme amounts of weight are gained
Some people are genetically predisposed to have more fat cells than others and women have more fat cells than men. An infant usually has about 5 – 6 billion fat cells. This number increases during early childhood and puberty, and a healthy adult with normal body composition has about 25 to 30 billion fat cells. A typical overweight adult has around 75 billion fat cells. But in the case of severe obesity, this number can be as high as 250 to 300 billion!
The average size (weight) of an adult fat cell is about 0.6 micrograms, but they can vary in size from 0.2 micograms to 0.9 micrograms. An overweight person’s fat cells can be up to three times larger than a person with ideal body composition.
Remember, body fat is basically just a reserve source of energy and fat cells are the like the storage tanks. Unlike a gas tank in your car which is fixed in size, however, fat cells can expand or shrink in size depending on how “filled” they are.