We studied the body mass index (BMI) of 986 patients who underwent potentially curative gastrectomy for gastric cancer at the National Cancer Center Hospital, Tokyo, in 1971, 1981, 1991, and 2001. The median BMI increased from 20.8 kg/m(2) in 1971 to 22.6 kg/m(2) in 2001 (P, 0.01). The increase was significant in both early and advanced gastric cancers, and in males, but not in females. The proportion of overweight patients (BMI > or = 25.0 kg/m(2)) increased from 9.2% in 1971 to 24.0% in 2001. Obese patients (BMI > or = 30.0 kg/m(2)) were rare. In conclusion, surgeons at the National Cancer Center Hospital, Tokyo, are increasingly having to operate on fat patients, but obese patients are still uncommon compared to the West.