Food reinforcement, motivation to obtain food, is associated with energy intake and obesity. Finding ways to decrease the reinforcing value of unhealthy foods may help with adherence to diets and weight loss. Our previous study in non-obese adults showed that daily consumption of the same snack food (food typically consumed outside of meals) for 14 days significantly decreased its reinforcing value. The purpose of this study was to replicate and extend these findings to obese individuals as well as to examine effects of different portion sizes of snack foods on food reinforcement. Thirty-one obese (body mass index > 30 kg/m2) and 27 non-obese (BMI < 30 kg/m2) women had food reinforcement and liking tested at baseline and after two weeks of daily consumption of either 0 kcal, 100 kcals, or 300 kcals daily of the same snack food.