This is relatively common in all populations enjoying an affluent lifestyle. The four major determinants are increasing age, obesity, ethnicity and family history. Large differences in prevalence exist based on these characteristics. In poor countries diabetes is a disease of the rich, but in rich countries it is a disease of the poor. The disease may be present in a subclinical form for years before diagnosis. The onset may be accelerated by the stress of pregnancy, drug treatment or intercurrent illness. Estimates of prevalence using the WHO criteria would suggest an overall prevalence of around 2% within the UK. Within the UK, type 2 diabetes is three to four times as prevalent in people of South Asian, African and Caribbean ancestry. High rates have also been found in people of middle Eastern or Hispanic American origin living western lifestyles. Unfortunately, people in westernized countries gain on average nearly 1 gram in weight every day of their adult life between the ages of 25-55 years. This gain, due to a tiny excess in energy intake over expenditure – 90 kcal or one chocolate-coated digestive biscuit per day – is the result of reduced exercise in a population rather than of increased food intake. Further, our sedentary lifestyle means that the proportion of obese young adults is rising rapidly, and epidemic obesity will create a huge public health problem for the future. The increasing numbers of obese adolescents presenting with type 2 diabetes is already a matter for concern in the USA and other parts of the world. Diabetes prevalence increases with age and 10% of people of Northern European stock will develop diabetes by the age of 70. This proportion rises towards 30% in those with a family history of diabetes and in those from some ethnic groups.

The insulin resistant state seen in type 2 diabetes tends to cluster with other conditions which increase cardiovascular risk. These include: hypertension, obesity, hypertriglyceridaemia, a decreased HDL-cholesterol, and the skin condition acanthosis nigricans. High insulin levels are characteristic. This has been called the insulin resistance syndrome, syndrome X or the metabolic syndrome. It seems likely that this is not a distinct entity but one end of a continuum in the relationship between exercise, lifestyle and bodyweight on the one hand, and individuals’ genetic make-up on the other – resulting in a state associated with adverse clinical consequences. About a third of the adult population have features of the syndrome, not necessarily associated with diabetes.