PURPOSE: To examine the association between young adulthood obesity and long-term risk of ischemic heart disease (IHD) and nonischemic congestive heart failure (CHF).METHODS: We conducted a population-based cohort study of 12,850 male conscripts whose fitness for military service was examined by Draft Boards in Northern Denmark. Outcomes were obtained from the Danish National Patient Registry, covering all Danish hospitals since 1977. Follow-up began on the 22nd birthday of each subject and continued until occurrence of an outcome, emigration, death, or on December 31, 2012, whichever came first. We used Cox regression to compute hazard ratios (HRs).RESULTS: The 36-year risk was 7.3% for IHD and 0.8% for CHF without pre-existing IHD among men of normal weight and 11.1% and 4.0% among obese men, respectively. Comparing obese men with men of normal weight, the adjusted HR was 1.63 (95% confidence interval [CI], 0.98-2.73) for IHD overall, 2.86 (95% CI, 1.56-5.25) for myocardial infarction, 5.52 (95% CI, 2.38-12.82) for unstable angina, 1.29 (95% CI, 0.69-2.41) for stable angina, and 6.68 (95% CI, 2.85-15.66) for CHF without pre-existing IHD.CONCLUSIONS: Young adulthood obesity was an important risk factor for IHD but also for CHF without pre-existing IHD.