Previous reports have shown that the Asp358Ala (T/G) polymorphism of the interleukin 6 receptor (IL6R) gene is associated with obesity and type 2 diabetes mellitus, but few studies have examined this association in the Japanese population. We performed the current study to investigate the relationship between the IL6R Asp358Ala (T/G) polymorphism and obesity in healthy Japanese men. Two hundred eighty-five healthy Japanese men (age, 46.1 +/- 11.5 years [mean +/- SD]; waist circumference [WC], 83.9 +/- 9.3 cm; body mass index, 23.3 +/- 3.3 kg/m(2)) employed by a Japanese company were enrolled in this study. Height, weight, and WC were measured, and daily energy intake levels were assessed by self-reported questionnaires. Genotyping of polymorphisms was performed by using melting curve analysis; no association was found between IL6R genotype and WC or body mass index. However, when the subjects were stratified by IL6R genotype, an association between WC and dietary energy intake level was found in the TT + GT-type subjects (P for linear regression = .048), but not in GG subjects (P for linear regression = .555). In addition, logistic regression analysis revealed that the interaction of IL6R (GG vs TT + GT) genotypes and dietary energy intake levels affected risk for abdominal obesity (P for interaction = .030). We concluded that the IL6R Asp358Ala (T/G) polymorphism appears to interact with energy intake and affect abdominal obesity in Japanese men. The interaction of this genotype and energy intake warrants further study.