Objective: Food reinforcement and delay discounting (DD) independently predict body mass index (BMI), but there is no research studying whether these variables interact to improve prediction of BMI. Methods: BMI, the relative reinforcing value of high (PMAX(HED)) and low (PMAX(LED)) energy dense food, and DD for $ 10 and $ 100 future rewards (DD10, DD100) were measured in 199 adult females. Results: PMAX(HED) (P = 0.017), DD10 ( P = 0.003), and DD100 (P = 0.003) were independent predictors of BMI. The interaction of PMAX(LED) x DD10 (P = 0.033) and DD100 (P = 0.039), and PMAX(HED) x DD10 (P = 0.038) and DD100 (P = 0.045) increased the variance accounted for predicting BMI beyond the base model controlling for age, education, minority status, disinhibition, and dietary restraint. Based on the regression model, BMI differed by about 2 BMI units for low versus high food reinforcement, by about 3 BMI units for low versus high DD, and by about 4 BMI units for those high in PMAXHED, but low in DD versus high in PMAXHED and high in DD. Conclusion: Reducing DD may help prevent obesity and improve treatment of obesity in those who are high in food reinforcement.