Introduction Of A High-fat/sucrose Diet Modulates Voluntary Wheel Running Activity In Adult Female Rats: 1559 Board #234 June 1 8

Food intake and spontaneous physical activity have been attributed to a common hypothalamic pathway although the specific mechanisms involved in this relationship, and how it is influenced, have yet to be elucidated. PURPOSE: To determine how alternating low- and high-fat/sucrose diets affect voluntary wheel running in rats and its relationship with food/energy consumption. METHODS: An interrupted time series model was used to examine voluntary running and ad libitum food consumption characteristics over a 9-week period in adult female (~40 days old; ~120-140 g) Sprague Dawley rats (n=8/group). Low- (L; 4%)- or high- (H; 25%) fat/sucrose diets were provided in 3-week intervals: LLL and HHH control groups received only low- or high-fat/sucrose diets, respectively, whereas alternating diet groups (HLH and LHL) were switched every 3 weeks. Resistance-free running wheels recorded distances automatically and food consumption was measured manually daily; body mass was recorded every two weeks. RESULTS: Each diet group increased mean running distance (meters/day) that peaked at Week 3 followed by a gradual decrease in activity through Week 9. Compared to other groups, LLL rats maintained a higher percentage of peak activity between Weeks 4-8. Daily distances were highly variable (range: 633 – 40,079 m/day) depending on the specific rat and day. Although daily food consumption ranged from 42-69 kcal/day, no relationship existed between daily running distances and absolute (grams) or relative (kcals) food consumption for the LHL, HLH, or HHH groups (R2 range: 0.0006 – 0.15); a significant correlation existed between these variables in LLL rats (R2: 0.58; p<0.05). Body mass increased from 61-80% from starting values and final body masses were similar in all groups (range: 225-240 g; P > 0.05). CONCLUSION: Adult female rats demonstrate a high propensity for voluntary physical activity in the first three weeks of wheel access followed by a natural tapering in activity, perhaps associated with age. Consumption of a diet high in fat and sucrose, regardless of when it was introduced during the 9-week protocol, blunted activity from peak values compared to rats that consumed a low fat-only diet (LLL), suggesting that diet composition, rather than intake alone, impacts spontaneous physical activity.