Fat is not readily stored in the body freely. Fat is stored in specialized cells known as adipocytes which enlarge in response to the fat content present. When fat is needed for energy, the adipocytes release their fat content to supply additional energy to the body.
When we gain weight, we don’t increase the number of adipocytes in the body. Rather, the adipocytes increase in size and volume in response to the amount of energy needed to be stored. It is the same mechanism when we lose weight, but the opposite. We reduce their size and volume by burning off the stored fats inside the adipocytes.
Lipolytic or fat dissolving injections break down fat cells. The obliterated fat cells will not grow back and, subsequently, will not recur. The remaining adipocytes will be the ones that will grow in response to certain conditions (also, depending on genetics and other factors, some areas are privileged for fat storage). The treated site will have less capacity for fat storage, which will result in the long-term efficacy of the treatment.
This means that treatment is expected to last indefinitely once you reach the desired results unless there is a tremendous increase in body weight and fat mass.