Despite evidence that weight loss improves the severity of coronary heart disease (CHD) risk factors, a direct association between weight loss and CHD incidence has not been demonstrated. In 1994-2001, the authors conducted an observational study of intentional weight loss as related to CHD incidence among patients recruited from a network of clinics in Israel who received nutritional counseling from a dietitian to support the medical recommendation to lose weight. Subjects were outpatients aged 50-75 years with a body mass index of > or =27 kg/m(2), without CHD or cancer but with at least one risk factor for CHD in addition to overweight. Outcomes were documented over 4 years by repeated weight measurements and by medical record verification. Among 1,669 patients, 224 (13.4%) incidents of CHD were recorded. For subjects who underwent at least 6 months of dietetic counseling, the risk-factor-adjusted odds ratio for CHD incidence associated with a weight loss of 4.5 kg (the median level of weight loss) was 0.57 (95% confidence interval: 0.39, 0.84). In this, the largest known study of its type reported to date, intentional weight loss from a 6-month diet predicted lower incidence of CHD over 4 years.