The increased risk of diabetes as weight increases has been shown by prospective studies in Norway(7), the United States (8), Sweden (9), and Israel (10). More recently, the Nurses' Health Study, using data based on self-reported weights, found that the risk of developing type 2 diabetes increases as BMI increases from a BMI as low as 22 (81). Since women in particular tend to under-report weight, the actual BMI values associated with these risks are likely to be higher than the Nurses' Health Study data would suggest. An association between type 2 diabetes and increasing relative weight is also observed in populations at high risk for obesity and diabetes, such as in American Indians (153, 154).
In recent studies, the development of type 2 diabetes has been found to be associated with weight gain after age 18 in both men (82) and women (81). The relative risk of diabetes increases by approximately 25 percent for each additional unit of BMI over 22 kg/m2 (83). Additionally, in a prospective study representative of the U.S. population, it was recently estimated that 27 percent of new cases of diabetes were attributable to weight gain in adulthood of 5 kg (11 lb) or more (84). Both cross-sectional (85-87) and longitudinal studies (82, 88, 89) show that abdominal obesity is a major risk factor for type 2 diabetes (82, 87).