Sex and individual differences in meal patterns mediate the persistency of running-associated high-fat diet avoidance in rats

Abstract

The modern environment is characterized by convenient access to a variety of high-fat (HF) foods and encourages excess energy intake, which leads to weight gain. While healthier diets and exercise are common interventions that facilitate energy balance, meal patterns also influence body weight and energy metabolism. The current study characterized the association among exercise, diet choice, and meal patterns in rats. Unlike sedentary rats, which prefer a HF to a chow diet, wheel-running rats initially avoid the HF diet. Subsequently, the running-induced HF diet avoidance persists longer in males than in females. We hypothesized that differences in meal patterns contribute to sex differences in the prevalence and persistency of HF diet avoidance. During two-diet choice, rats did not mix chow and HF diet within a meal and consumed discrete meals of each diet. Exercise decreased chow meal size in both sexes (4.5 vs. 5.7 kcal) but decreased total meal frequency only in male rats. Analyses of individual differences revealed WR rats that maintained HF diet avoidance (HF avoiders) had larger chow than HF meals (5.2 vs. 1.3 kcal) upon initial 3 days of diet choice. When compared with rats that reversed HF avoidance (HF eaters), HF avoiders had shorter latency to consume their first meal of HF diet (2.6 vs. 98.9 min) upon initial running and diet choice. Taken together, these results suggest that both sex and individual differences in meal patterns contribute to differences in the persistency of exercise-associated HF diet avoidance.

Role of glucocorticoid signaling in exercise-associated changes in high-fat diet preference in rats

“…Detailed behavioral results were reported in our previous publications (90,91). Figure 7, A and B, summarizes the HF diet preference patterns throughout the two-diet choice period for Sed and WR rats in both sexes [sex ϫ HF eater/avoider ϫ time F(34,527) ϭ 2.83, P Ͻ 0.0001].…”

“…7. Behavioral results of experiment 3 where the two-diet choice period was 15 and 18 days, respectively, from 2 previous studies (90,91). A three-way mixed model ANOVA with sex, high-fat (HF) eater/ avoider, and time (15 days) with cohort as the covariate was used to analyze the first 15 days of diet choice.…”

“…Subjects. Subjects included both male and female rats from two previous experiments that underwent two-diet choice and WR for 15 (90) and 18 (91) days, respectively. More females than males reversed HF diet avoidance and the reversal of HF diet avoidance occurred earlier in females than males (see Fig.…”

“…TISSUE EXTRACTION. Bilateral brain micropunches of Sed (n ϭ 14/sex) and WR (n ϭ 18/sex) rats of both sexes (90,91) were collected using a cryostat. Briefly, the forebrain and hindbrain were blocked around the midbrain caudal to the ventral tegmental area.…”