The medical complications of obesity

The prevalence of overweight and obesity is increasing worldwide. 1 A comparison of data from 1976–802 with that from 1999–2000 shows that the prevalence of overweight (defined as body mass index, BMI, of 25–29. 9 kg/m2) increased from 46% to 64. 5%, and the prevalence of obesity (BMI ⩾ 30 kg/m2) doubled to 30. 5%. The epidemic of obesity is not just isolated to the US, but is worldwide, 3, , 4 including less affluent countries. 4 Obesity and overweight have many causes, including genetic, metabolic, behavioural and environmental. The rapid increase in prevalence suggests that behavioural and environmental influences predominate, rather than biological changes. We summarize data from many studies evaluating the impact of obesity on mortality and morbidity, discuss some controversies and provide practical guidelines for managing obese patients. Direct associations between obesity and several diseases, including diabetes mellitus, hypertension, dyslipidaemia and ischaemic heart disease, are well recognized. Despite this, the relationship between body weight and all-cause mortality is more controversial. A very high degree of obesity (BMI ⩾35 kg/m2) seems to be linked to higher mortality rates, 5 but the relationship between more modest degrees of overweight and mortality is unclear. Initial data from actuarial studies of more than 4 million men and women showed a direct positive association between body weight and overall mortality rates. 6 Subsequent studies confirmed increased mortality risk above a certain threshold, but found a U-shaped association between weight and mortality. 7, , 8 In the Build study, 9 there was a higher mortality in lean subjects, but there was no adjustment for smoking. The American Cancer Society found a much stronger association between leanness and mortality, specifically cancer mortality, in the group of smokers compared to non-smokers. 10 The Harvard Alumni Study11 was a prospective cohort study of more than 19 000 middle-aged … Address correspondence to Dr S. D. H. Malnick, Department of Internal Medicine C, Kaplan Medical Centre, Rehovot 76100, Israel. email: stevashattrendline. co. il