Obesity is associated with metabolic disorders and cardiovascular diseases. This study investigated the relationship between overweight and obese status and the incidence of type 2 diabetes, hypertension, hyperlipidemia and hyperuricemia. Methods: This prospective cohort study comprised 1749 hospital employees who received baseline health check-ups in 1993. Data from the 1027 participants (832 women, 195 men; mean age, 36 ± 7 years) who repeated check-ups in 2003 were used in the analysis. Relative risks (RRs) for development of metabolic disorders during follow-up associated with different body mass index (BMI) categories at baseline as defined by Asia-Pacific recommendations and the Department of Health in Taiwan were calculated after adjustment for covariates. Results: The prevalence of overweight and obesity at baseline check-up were 17.6% and 14.5%, respectively. Obese subjects with baseline BMI ≥ 25 kg/m2 had a significant multivariate-adjusted RR of 2.7 for hypertension, 14.8 for type 2 diabetes, 3.2 for hypertriglyceridemia, and 2.8 for hyperuricemia, compared to subjects with baseline BMI < 23.0 kg/m2. RR for diabetes was higher in women than in men, but RR for hypertriglyceridemia was higher in men. The risks of hypertension and hyperuricemia significantly increased for subjects with baseline BMI ≥ 23 kg/m2, while RRs for type 2 diabetes increased significantly for baseline BMI ≥ 24 kg/m2 and hypertriglyceridemia increased for baseline BMI ≥ 25 kg/m2. The risks attributable to obesity (baseline BMI ≥ 25 kg/m2) were 23.0% for hypertension, 70.8% for diabetes, 27.9% for hypertriglyceridemia, and 24.1% for hyperuricemia. Conclusion: This study revealed that a high prevalence of overweight and obesity was associated with significantly increased risk of development of type 2 diabetes, hypertension, hypertriglyceridemia and hyperuricemia in hospital employees, suggesting the need for programs to improve weight management.