As a person is continuously in positive energy balance and beings to deposit excess body fat, lipid gets deposited in existing adipocytes causing them to enlarge or hypertrophy. Adipocyte hypertrophy causes the formation of new adipocytes, also known as adipocyte proliferation. What happens to this person's adipocyte size and number when they are in negative energy balance and lose weight?

The adipocytes, also known as the fat cells are very large in concentration. In the negative energy balance, like when the expenditure of energy is taking place, the initial energy source is the fats accumulated in the adipocytes.

There are two enzymes taking part in the procedure, that is, the adipose glyceride lipases and the hormone-sensitive lipase. In the procedure, the fats accumulated in the adipose cells get lost. This leads to shrinkage of the adipose cells, while the number of adipose cells stays similar.