| The heavy consumption of high-sugar/fat foods, especially sugar-rich items, is important in the
establishment of a binge episode and maintenance of a pattern of binge eating. Recurrent sugar
and fat exposure, whether from frequent binging or daily diet, has been shown to alter executive
function and reinforcement processes that affect self-regulation. Reinforcement processes can be
examined through delay discounting (DD)—a pattern of preferences for smaller more immediate
reinforcers over larger delayed reinforcers. Delay discounting is associated with obesity and
binge eating in humans, but the role of diet has not been examined experimentally. The present
study systematically examined the extent to which high-sugar diets combine with bingeproneness in rats to affect DD. Female Sprague Dawley rats (N = 32) served as subjects. Bingeproneness was determined by examining consumption of Oreo Double Stuf® cookies in 4-hour
periods; rats that reliably consumed the highest and lowest kilocalories were classified as bingeeating prone (BEP) and binge-eating resistant (BER), respectively. Rats were then randomly
assigned to one of two diet conditions: chow-only or an Oreo-plus-chow (high-sugar) diet.
Baseline DD was measured by presenting rats with choices between one sucrose pellet delivered
immediately versus three sucrose pellets delivered after a systematically increasing delay. Rats
then completed a cookie-morsel exposure condition in which they consumed one gram of Oreo
cookie immediately before a second DD session. Results showed the cookie morsel induced
higher DD compared to baseline for all subjects. There were no significant main effects of bingeproneness nor diet on DD. However, a significant binge-proneness × diet interaction was
observed. Binge-eating prone rats given the chow-only diet exhibited significantly higher DD
than BEP rats given the Oreo-plus-chow diet. This diet-based effect was not detected for BER rats. These findings indicate, consistent with a binge episode, that exposure to highly palatable
food induces DD. These findings also suggest that limited but consistent access to sugar may
serve as a protective factor that decreases food DD for organisms prone to binge eating, lending
support for flexible dieting rather than rigid dieting for these individuals.
Keywords: binge eating; binge-eating prone rats; delay discounting; highly palatable food; highsugar diet |