Low basal metabolic rate (BMR) is a risk factor for weight gain and obesity. The polymorphism at codon 64 of the β3-adrenergic receptor gene has been suggested to be associated with BMR. We investigated the frequency of the Trp64Arg of the β3-adrenergic receptor gene and the effects of this polymorphism on BMR in obese Finns. Altogether, 170 obese subjects (29 men, 141 women, BMI 34.7 ± 3.8 kg/m2, mean ± SD) participated in the study. The frequency of the Trp64Arg polymorphism was 19%. None of the obese subjects were homozygous for the Arg-encoding allele. The frequency of the Trp64Arg polymorphism in obese Finns did not differ from nonobese and normoglycemic control subjects. BMR adjusted for lean body mass and age was lower in subjects with the Trp64Arg polymorphism (n = 20) than in normal homozygotes Trp64Trp (n = 99) (1,569 ± 73 vs. 1,635 ± 142 kcal/day, P = 0.004). For the female group (n = 98), the respective values were 1,501 ± 66 kcal/day vs. 1,568 ± 127 kcal/day (P = 0.004). There were no significant differences in weight, BMI, waist-tohip ratio, lean body mass, percentage of fat, and respiratory quotient between the groups with or without the Trp64Arg polymorphism. Neither serum glucose nor insulin levels differed between the two groups. We conclude that the Trp64Arg polymorphism of the β3-adrenergic receptor gene affects basal metabolic rate in obese Finns but does not have significant effect on glucose metabolism.

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