At what age does your body start increasing the size of existing fat cells?

During infancy and adolescence, adipose tissue is growing by a combination of the increase in fat cell size (to a lesser extent) and (above all) the number of these cells. In adults, fat cell number is constant over time in spite of a large turnover (about 10% of the fat cells per year) when body weight is stable.

answer: our bodies are made up of mostly water, we rely on it to regulate our body funtions.