Impact of dietary protein and gender on food reinforcement

Authors: Casperson, Shanon; Roemmich, James

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2017
Publication Date: 8/30/2017
Publication URL: http://handle.nal.usda.gov/10113/5832842
Citation: Casperson, S.L., Roemmich, J.N. 2017. Impact of dietary protein and gender on food reinforcement. Nutrients. doi:10.3390/nu9090957.

Interpretive Summary: Recent evidence suggests that increasing dietary protein may alter reward-driven eating behavior. Our research project focus was to determine if increasing protein intake alters the reinforcing value (RRV), an objective measure of food reinforcement, of high calorie snack foods. Healthy adults were given meals with either a typical amount of protein (15%) or a high amount of protein (30%). We then measured how hard they were willing work for a small serving of their most liked sweet (e.g. candy) and savory (e.g. chips) snack foods using a computer-based choice game. We found that for women eating a high protein meal significantly decreased their wanting (RVV) of savory snack foods. This effect was not seen in men. We also found that increasing protein intake does not change the wanting of sweet snack foods. One implication of this research is that eating more protein can change eating behavior in women. Another implication of this research is that the highly reinforcing properties of sugar are difficult to overcome.

Technical Abstract: Recent evidence suggests that increasing dietary protein may alter reward-driven eating behavior. However, the link between protein and food reinforcement is not known. We sought to determine the extent to which increasing dietary protein alters food reinforcement in healthy adults. In a randomized crossover study, 11 women (age = 25 ± 7y; BMI = 21 ± 2kg/m2) and 10 men (age = 22 ± 2y; BMI = 24 ± 2kg/m2) consumed normal (15%) and high (30%) protein meals. Food reinforcement was assessed using a computer-based choice task (operant responding with concurrent log2(x) reinforcement schedules) 4h after lunch. We found that food reinforcement was greater in men than women (p < 0.05) and greater for sweet than savory snack foods (p < 0.02). Gender interacted with dietary protein level (p = 0.03) and snack food type (p < 0.0001). Specifically, we found that increasing dietary protein decreased the reinforcing value of savory foods in women. The reinforcing value for sweet foods did not interact with dietary protein or gender. These results demonstrate the differential effects of dietary protein on the reinforcing value for energy-dense, highly palatable snack foods.