11/04/2025
The Science of Fat — Here's What Happens to Your Body When Lose Weight
When you lose weight, your fat cells do not burn or disappear. They simply shrink in size.
When you consume more calories than your body needs for its daily activities, the excess calories are stored in fat cells.
As these cells store more fat, they expand in size, leading to weight gain. However, when you consume fewer calories than your body uses, it starts to use stored fat for energy. This causes fat cells to release their stored fat content, leading to a reduction in their size.
The number of fat cells remains relatively constant. The process of gaining or losing weight typically involves changes in the size of fat cells, not the number. While it's possible to increase the number of fat cells (a process known as hyperplasia), this is less common and usually occurs under specific conditions, such as extreme and prolonged excess calorie intake. In adults, the number of fat cells is relatively stable.
Even after significant weight loss, the number of fat cells tends to remain constant; they just become smaller. There are certain medical procedures, like liposuction, that can physically remove fat cells from the body. However, these procedures do not affect the body's overall tendency to store fat, and new fat cells can form if the underlying causes of weight gain are not addressed.
If you lose fat quickly with crash diets or intensive weight-loss regimes, your fat cells will become more prone to regaining that fat later on. This may explain why some people regain a substantial portion, if not all, of the weight they initially lost.
