Sex differences in exercise-mediated changes in diet preference and its associated cognitive and metabolic outcomes
The modern environment contributes to the obesity epidemic by encouraging a sedentary lifestyle and increased intake of highly processed, energy dense foods. Females are more prone to develop disordered feeding behaviors, such as binge eating, and the prevalence of obesity is greater in females than males. However, obesity-related metabolic and cognitive dysregulation is more severe in males. One mechanism by which exercise may protect against these negative outcomes and restore energy homeostasis is through changes in macronutrient selection, specifically decreasing intake of high fat (HF) food. Sex differences in the susceptibility, outcomes, and exercise as a treatment intervention for obesity, however, have not been well-characterized. Moreover, how factors including diet, cognition, and peripheral metabolic function interact to potentially perpetuate the viscous feedback loop of maladaptive eating behavior and obesity in a sex-specific fashion is poorly understood. The goal of this dissertation was to investigate sex differences in the efficacy of exercise at attenuating the adverse cognitive and metabolic outcomes associated with long-term HF feeding. To this end, our lab has established a voluntary wheel running (WR) and two-diet choice model in rats. Using this paradigm, we found that the simultaneous introduction of WR and HF diet resulted in complete HF diet avoidance in WR rats whereas sedentary (Sed) rats maintained HF diet preference. There is also a sex difference in exercise-mediated changes in diet preference where male rats maintain HF diet avoidance and females reverse their initial HF diet avoidance. Chapter 2 examines the role of gonadal hormones on the expression and maintenance of HF diet avoidance during acute exercise. Chapter 3 extends the voluntary WR and two-diet choice paradigm used in Chapter 2 to assess sex differences in peripheral metabolic function and behavioral flexibility resulting from chronic HF feeding. In Chapter 4, an additional assessment of cognitive behavior was added where heightened impulsivity, a behavior associated with poor dietary self-regulation, binge eating, and obesity, was examined as both a potential vulnerability factor for and outcome of palatable diet preference. To more accurately mimic the fat and carbohydrate intake in the modern environment, HF was replaced with a Western diet (WD). Impulsive choice was assessed before and after long-term WD exposure and preference in addition to WD-mediated metabolic adaptions. Results suggest that female, but not male, sex hormones as well as developmental factors are important for the expression of sex-typical diet choice patterns during exercise. The ability for exercise to improve peripheral metabolism, including glucose tolerance and insulin sensitivity, was greater in males than females. Although cognitive performance was only moderately improved in rats of both sexes, exercise did appear to have a beneficial effect on cognition. Taken together, the studies in this dissertation contribute to the knowledge of how sex differences in diet preference and exercise interact and lead to sex-specific physiological and behavioral adaptations.
wheel running, exercise, diet choice, high fat diet, sex differences, behavioral flexibility, impulsivity, insulin sensitivity
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign