PURPOSE: Most studies comparing the effects of fitness and fatness on cardiovascular (CVD) risk have been done with young, healthy participants with low rates of obesity and high levels of fitness. The present study examined the association of cardiorespiratory fitness and obesity with CVD risk factors in an ethnically diverse sample of overweight/obese individuals with type 2 diabetes. METHOD: Baseline data from Look AHEAD, a study of 5145 overweight or obese individuals with type 2 diabetes, were used to examine the association of BMI categories (overweight, class I, II, or III obesity) and cardiorespiratory fitness (assessed with a maximal graded exercise test and categorized by age- and gender-specific quintiles) on cardiovascular risk factors and on the odds of having hypertension, hyperlipidemia, or HbA1c ≥ 7%. RESULTS: BMI categories and fitness quintiles were highly associated with each other (P < 0.0001), with the heaviest participants being the least fit. Only 2-3% of participants had class III obesity and were in the two fittest quintiles or, conversely, were overweight and in the two least-fit quintiles. When fitness and BMI were included in the same model (adjusting for age, smoking, diabetes duration, and race), HbA1c, ankle/brachial index (ABI), and Framingham risk score were most strongly associated with fitness. Systolic blood pressure was most strongly associated with BMI category. Similar results occurred when waist circumference and fitness were considered together. CONCLUSION: In this large, ethnically diverse sample of overweight/obese individuals with type 2 diabetes, fitness and fatness were highly related to each other but seemed to have different impact on specific CVD risk factors. ©2007The American College of Sports Medicine.