Impact of diet and exercise training on physical performance and body composition in male rats: influence of ad libitum feeding and mild caloric restriction

Background: Improvements in body composition have been reported when men and women switch from consuming a Western Diet (WD) to a purified and “clean” diet (PD) known as a "Daniel Fast.” While no laboratory studies have determined physical performance improvements following the Daniel Fast, numerous anecdotal reports of improved physical capacity and well-being have been noted. Methods: In the present study, Long-Evans rats (N=28) were assigned to be exercise trained (+E) by running on a treadmill three days per week or to act as sedentary controls. After baseline physical performance was evaluated by recording run time to exhaustion, half of the animals in each group were fed for 12 months either a PD formulated to mimic the Daniel Fast, or a WD. Food was provided ad libitum during months 1-3 and was restricted to 90% of animals’ daily needs during months 4-12. Physical performance was evaluated again at the end of months 3, 6, 9, and 12, as was body composition and bone mineral density using dual energy x-ray absorptiometry. Results: As expected, exercise resulted in an increase in run time as compared to the non-exercise control animals (p<0.05). Dietary intake did not influence run time. Body composition was largely impacted by diet composition, with the PD resulting in less total mass and fat mass as compared to the WD (p<0.05), with only small differences noted in lean mass between diet groups. Bone mineral density increased in a linear fashion from months 3-12, with no differences noted based on diet or exercise training. Conclusion: A WD, with and without exercise, results in increased total and fat mass in male rats. A PD allows animals to maintain a relatively low body fat, without leading to adverse outcomes pertaining to lean body mass or bone mineral density.