Abstract The β3-adrenergic receptor (ADRB3) is expressed mainly in visceral adipose tissue and is thought to contribute to lipolysis and the delivery of free fatty acids to the portal vein. Although many studies have examined the relationship between the Trp64Arg mutation of ADRB3 and obesity, the results have been inconsistent. We examined the cross-sectional relationship of ADRB3 variants with indexes of obesity, and their longitudinal changes over 10 yr, in men and women, aged 40–69 yr, who were randomly selected from the Japanese rural population. The study considered both dietary energy intake and physical activity levels. Among the 746 participants, the genotype frequencies of the Trp64Trp, Trp64Arg, and Arg64Arg variants were 483, 224, and 39, respectively. The cross-sectional analysis showed no significant differences in height, weight, body mass index, blood pressure, serum total and high density lipoprotein cholesterols, and hemoglobin A1c among the genotype groups even after adjustments for gender, age, smoking, alcohol drinking, physical activity, and energy intake. No significant differences in the weight changes between the genotype groups were evident in the longitudinal analysis. We conclude that the Trp64Arg mutation of ADRB3 has little or no influence on either body weight or body mass index in the general Japanese population.