Obesity is a rapidly growing global problem. It is not simply the result of eating too much, and not all types of obesity have the same significance. Obesity is in part genetic, and one particularly important genetic type of obesity is the tendency to ‘truncal obesity’,—that is, a raised waist-to-hip ratio. Such obesity is powerfully associated not only with a tendency to diabetes, but also to cardiovascular disease, (‘Syndrome X’). Interestingly, this is the type of obesity seen in every hunter–gatherer (HG) population around the globe. Such people are intolerant of carbohydrate, especially refined carbohydrate, especially in the excessive amounts typically consumed in affluent societies. In such pure HG communities, rates of diabetes can be as high as 50%, when the ‘Western’ lifestyle is adopted. Many of us, however, share some of their genes and their carbohydrate intolerance—perhaps as many as 20 or 30% of the world’s population. Pregnancy can uncover this characteristic, and obesity and glucose intolerance in pregnancy are rapidly burgeoning problems. Quite contrary to the common nutritional dogma of encouraging regular carbohydrates, it is suggested that pregnant women with a high waist-to-hip ratio should be strongly advised to adhere to a low-glycaemic-index diet. Additionally, many dietary interventions, some of them derived from observation of HG populations, are of proven benefit in reducing the expression of glucose intolerance and may well help in tackling the obesity epidemic.