The purpose of a fat cell is to store small droplets of fat molecules. These fat molecules are formed as the concentrations of fatty acids in the blood rises, such as after a big meal. An increase in concentrations within the blood triggers lipase enzymes located in fat tissue, to grab the fatty acids and convert them into a fat molecule (triacylglycerols) for storage.
As we gain weight and become fatter, the fat cell numbers do not multiply, rather they just store more fat molecules – they expand.
Fat cells in the human can multiply, but only if fat storage cells “run out”.
The majority of stored fat on the human body is present under the skin, or as subcutaneous body fat. A human can have anywhere between 50 – 200 billion fat cells.
There is also fat storage around the kidneys, liver and even inside muscle. In fact, as we age, fat storage within muscle tends to increase and means we don’t notice an increase in this area like we do when it’s placed around the waist.