The application of magnetic resonance imaging and computed tomography to obesity research has changed the focus from body mass and skinfold thickness to abdominal fat mass and visceral adiposity. Intra-abdominal fat constitutes less than 20% of total body fat but is a major determinant of fasting and postprandial lipid availability because of its physiological (lipolytic rate and insulin resistance) and anatomical (portal drainage) properties. High levels of serum free fatty acids, as a result of abdominal obesity, cause excessive tissue lipid accumulation and contribute to dyslipidaemia, beta cell dysfunction, and hepatic and peripheral insulin resistance. An individual's risk of non-insulin dependent diabetes mellitus and cardiovascular disease relates closely to the inheritance of central obesity and susceptibility to tissue lipotoxicity.