Background

Forced treadmill exercise consistently reduces high fat diet intake in male but not female rats, resulting in an attenuation of weight gain over time in exercising male rats compared to sedentary controls. It is unknown whether the reduction in caloric intake, seen in males, will translate in the presence of highly palatable foods. We hypothesized that exercising male rats would display an attenuated intake of the lipid but not sucrose solution in line with the reduction we observe in male HFD intake.

Methods

Male and female Wistar rats were fed a high fat diet for 6 wks then randomized to sedentary conditions or forced treadmill exercise (15m/min, 60min/day, 5 days/wk, for 4 wks). Rats were provided access to isocaloric solutions of both sucrose, and intralipid in their home cage for 1 hour at the start of the dark cycle for 7 days (4 days with exercise, 3 days where exercisers were rested). During this time frame, rats had ad libitum access to high fat diet and water. 24hr high fat diet intake was measured daily.

Results

Regardless of sex or activity status, all rats overconsumed on average 15.0 ± 1.3 kcals when presented with the individual macronutrients. There was no difference in preference between the sucrose and lipid solutions. Exercisers consumed more of both solutions on the days they were rested (Males: 28.7 ± 2.1 Females: 27.7 ± 1.7, kcals) as compared to the days they exercised (Males: 24.9 ± 1.8 Females: 23.0 ± 1.8, kcals) or in comparison to sedentary controls (Males: 24.2 ± 2.3 Females: 25.4 ± 1.9, kcals) (p<0.001).

Conclusions

Exercise did not prevent overconsumption of highly-palatable carbohydrate or lipid solutions. On rest days, exercisers consumed more of the palatable solutions suggesting possible hedonic substitution in the absence of exercise.