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 (PMAXHED) and low (PMAXLED) energy dense food, and DD for $10 and $100 future rewards (DD 10, DD100) were measured in 199 adult females. Results PMAXHED (P = 0.017), DD10 (P = 0.003), and DD 100 (P = 0.003) were independent predictors of BMI. The interaction of PMAXLED × DD10 (P = 0.033) and DD100 (P = 0.039), and PMAXHED × 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. Copyright © 2013 The Obesity Society.