Obesity is associated with the development of some of the most prevalent diseases of modem society. The greatest risk is for diabetes mellitus where a body mass index above 35 kg/m 2 increases the risk by 93-fold in women and by 42-fold in men. The risk of coronary heart disease is increased 86% by a 20% rise in weight in males, whereas in obese women the risk is increased 3.6-fold. Elevation of blood pressure, hyperlipidaemia and altered haemostatic factors are implicated in this high risk from coronary heart disease. Gallbladder disease is increased 2.7-fold with an enhanced cancer risk especialty for colorectal cancer in males and cancer of the endometrium and biliary passages in females. Endocrine changes are associated with metabolic diseases and infertility, and respiratory problems result in sleep opnoea, hypoventilation, arrhythmias and eventual cardiac failure. Obesity is not a social stigma but an actual disease with a major genetic component to its aetiology and a financial cost estimated at $69 billion for the USA alone.