The objective of this study was to investigate the effects of physical activity and regular exercise on the reduction in body fat by the addition of catechins in a controlled clinical trial. The study involved 4 weeks of a run-in period and 12 weeks of a test period. Healthy male subjects (n = 192, mean age .+-. SEM ; 39.0 .+-. 0.6 yr, mean BMI ; 24.9 .+-. 0.2 kg/m2) ingested a beverage containing 0 mg, 278 mg, 570 mg or 845 mg catechins per day during the test period. Body indices, abdominal fat area by CT scan, blood parameters, physical activity and exercise habits were measured. As observed for a form of green tea or oolong tea beverage, it was confirmed that body fat was reduced by the long term intake of catechins in a form of the sports drink without any safety concerns. A significant correlation was observed between the dosage of catechins and changes in the anthropometric parameters at week 12. Furthermore, the 0 mg and the 570 mg groups were subclassified by the criterion of the number of steps of 9,000 per day or the presence or absence of exercise habits, and changes in anthropometric parameters were compared among these subgroups. It was found that body fat was effectively reduced by the long term intake of catechins in combination with physical activity or regular exercise at a conventional level of health promotion activity. These results suggest that the intake of catechins, combined with physical activity or exercise habits, might be useful for the prevention and improvement of life-style related diseases, mainly obesity.