OBJECTIVE: To examine the relationship between body mass index (BMI) and health-related quality-of-life (HRQL), in the presence of dietary controls and/or exercise in a national sample in the United States. METHODS: BMI and its association with HRQL domains ( physical, mental and activity limitations) were examined using the Centers' for Disease Control and Prevention's 2000 Behavioral Risk Factor Surveillence System (BRFSS) data, after adjusting for various sociodemographic factors, self-reported health-status, and diet/exercise behavior. RESULTS: Based on World Health Organization's ( WHO) classification of obesity, the study sample (N = 182 372) included approximately 43.7% nonoverweight, 36% overweight, 14% obese, and 7% severely obese respondents. Exercise and dietary modifications were used by 17.5% of overweight, 15.2% of obese, and 12.5% of severely obese individuals. Logistic regression results using nonoverweight BMI as the reference category showed that severely obese (OR = 1.87, 95% CI 1.64 - 2.12) and obese (OR = 1.21, 95% CI 1.09 - 1.33) were more likely to experience greater than 14 unhealthy days affecting the physical health domain. Severely obese (OR = 1.41, 95% CI 1.26 - 1.59) and obese (OR = 1.17, 95% CI 1.07 - 1.28) were also more likely to experience greater than 14 unhealthy days affecting the mental health domain. Similarly, severely obese (OR = 1.73, 95% CI 1.50 - 1.99) and obese (OR = 1.22, 95% CI 1.08 - 1.37) were more likely to experience greater than 14 days with activity limitations. Exercise and dietary controls were associated with better HRQL across all three domains. CONCLUSION: The study highlights the relationship between BMI and HRQL in the United States. The study also underlines the positive correlation of exercise and dietary modifications with HRQL.