This study measured caffeine-induced changes in activated sweat gland density (ASGD) and fat oxidation using a randomized crossover design with 10 healthy volunteers given caffeine (Caffe-I, 3 mg/kg ingested 30 min before experiment) and non-caffeine (No-Caff). Subjects were $173.0pm3.2$ cm in height, $72.5pm4.3$ kg in weight, and $21.0pm2.5$ years in age. All experiments were performed in an automated climate chamber ($24.0pm0.5^{circ}C$, relative humidity $50pm3%$, air velocity less than 1 m/sec) between 2-5 p.m. The ASGD on the chest, upper arm, upper back, and lower back were measured (after 30 min running at 60% $VO_{2max}$), and blood samples were taken (at 40 min before, immediately before and after 30 min running). Activated sweat gland density levels were higher in Caffe-I (Chest p<0.05 and U-Back p<0.01) and free fatty acids (FFA) were higher in Caffe-I compared to No-Caff immediately before (p<0.05) and after running (p<0.01). In summary, caffeine increases ASGD and FFA by stimulating the sympathetic nervous system and increasing of lipolysis.