The Republic of Palau belongs to Micronesia, and obese people and lifestyle-related diseases are prevalent there. We investigated the relationship of dietary habits and obesity to oxidative stress in Palauan people, as compared with those of Japanese and Mongolian people. A total of 126 healthy Palauan subjects were enrolled. Oxidative stress was evaluated by serum level of reactive oxygen metabolites (ROM). Antioxidant capacity was evaluated by serum level of biological antioxidant potential (BAP). In Palauan subjects, BMI> or =30 was observed in 45.0% of males and 59.1% of females (Japanese: males 1.3%, females 0.8%, Mongolian: males 6.3%, females 14.7%). Palauan subjects consumed 2553 kcal per day (Japanese 2121 kcal, Mongolians 2534 kcal). The ratios of carbohydrate energy to total energy were 59.8 % (Japanese 54.7 %, Mongolians 50.2%). The ratios of fat energy to total energy were 22.9% (Japanese 26.7%, Mongolians 34.5%). ROM levels in Palauan subjects showed higher than those in Japanese subjects, while BAP levels of Palauan subjects did not decrease compared to those of Japanese. ROM levels correlated with body fat ratio, and showed a reverse correlation with handgrip strength. Handgrip strength decreased in the subjects of more than forty years of age. These findings suggest that the obesity in Palauan people may have a connection with high intake of calories through carbohydrate eating rather than through fat eating. Their high oxidative stress may be induced by obesity, and contribute to an early decline of handgrip strength, ultimately in early aging.