The adipocyte, which is the cellular basis for obesity, may be increased in size or number in obese persons. Hypertrophic obesity, characterized by enlarged fat cells, is typical of android abdominal obesity. Hypercellular obesity is more variable than hypertrophic obesity; it typically occurs in persons who develop obesity in childhood or adolescence, but it is also invariably found in subjects with severe obesity.

Hypertrophic obesity usually starts in adulthood, is associated with increased cardiovascular risk, and responds quickly to weight reduction measures. In contrast, patients with hypercellular obesity may find it difficult to lose weight through non-surgical interventions.