Effects of caffeine and exercise on body fat levels of the rat.

Caffeine stimulates a release of free fatty acids from adipose tissue and has been shown to enhance fat utilization during an acute bout of prolonged aerobic exercise. A previous study indicated that chronically ingesting caffeine prior to exercise in an aerobic training program may enhance the fat-reducing effects of exercise. In the present study, mature male rats were divided into four groups: two groups swam 90 min/day, 5 days/week for 10 weeks (caf-ex, no caf-ex), while two groups served as sedentary controls (caf-sed, no caf-sed). The groups that received caffeine were administered, by gavage, 5 mg caffeine/kg body weight, dissolved in saline, 45 min prior to the start of exercise. The no caf groups received saline only. After the training period, body fat weight was determined by petroleum ether extraction of the fat from a dried, homogenized sample in a soxhlet apparatus. Body weight, percent body fat, epididymal fat pad weight, and food intake were all significantly lower in the exercised groups than the sedentary groups (P less than 0.05). The exercised groups weighed approximately 50-70 g less, % BF was 3.4% lower, EFP were approximately 2.5 g lighter, and food intake was 49-66 g less. There was no statistically significant difference between the caffeine and no caffeine groups on any of the variables tested (P greater than 0.05). This study did not find that caffeine enhanced the fat-reducing potential of the aerobic exercise.