OBJECTIVES: To examine prevalence of chronic comorbid diseases among obese adults in the United States METHODS: Medical Expenditure Panel Survey Data from 2005 – 2007 was used for the analysis. Adults with age ≥ 20 years and BMI ≥ 30, were defined obese. Unadjusted age-specific prevalence of hypertension, diabetes, dyslipidemia, CHD, osteoarthritis and asthma were obtained among obese, non-obese and entire population using descriptive analysis. Adjusted prevalence estimates were obtained using regression analysis after controlling for socio-demographic factors. Age-specific prevalence ratios (relative risk) were obtained by taking ratios of predicted prevalence rates for obese versus non-obese individuals. Bootstrapped 95% confidence intervals were generated for prevalence ratios.  RESULTS: Among obese adults the unadjusted prevalence of hypertension was (34.40%), followed by dyslipidemia (21.87%), diabetes (16.34%) and asthma (6.92%). Adjusted prevalence of chronic diseases was always higher among obese as compared to non-obese and the entire population. The prevalence ratio for diabetes was 3.06 (95% C.I: 2.82 – 3.30) at the age of 20 and was 2.20 (95% C.I: 2.09 – 2.31) at 70 years. At any age, obesity increases the likelihood of these conditions by at least 50% as compared to non-obese individuals.  CONCLUSIONS: Prevalence ratios indicate that obesity has highest impact on prevalence of diabetes; followed by hypertension, osteoarthritis, dyslipidemia. Study findings suggest that obesity is not only a disease, but may also be a cause for other chronic disorders. There is a need to develop effective interventions to combat obesity and thus minimize its impact on other diseases in United States.