Association between the FTO gene and overweight in Japanese children and adolescents

The association between the fat mass- and obesity-associated (FTO) gene and a predisposition to obesity is inconsistent in adult Asian populations. We investigated the association of the FTO gene with weight status in Japanese children and adolescents.

Nested case-control study and 3-yr longitudinal study - In the Shunan Child Cohort Study, fifth and eighth grade students attending all schools of Shunan completed the questionnaires. Overweight, including obesity, was defined as a percentage of overweight of 20% or in accordance with the International Obesity Task Force. We recruited 133 obese subjects and randomly selected controls from the 2006 cohort. We genotyped three FTO single nucleotide polymorphisms (SNPs): rs3751812, rs9939609, and rs1558902.

The three genotyped SNPs were in tight linkage disequilibrium, with the exception of one case. The minor SNP allele of rs3751812 conferred a predisposition to obesity, and its odds ratio was 2.2 [95% confidence interval (CI), 1.5-3.4] in the additive model and 2.7 (95% CI, 1.6-4.4) in the dominant model (p < 0.001). Although blood parameters and some lifestyle behaviors were significantly different between the cases and controls (p < 0.01), these traits were not significantly different among the genotypes. In addition, we did not find an association between the genotypes and body mass index change during the 3 yr.

The FTO gene is associated with the early onset of overweight in the Japanese population as well as in European populations. The results suggest that obesity-related risk factors in fifth and eighth graders appear because of their overweight status.