Answer:
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.