(HealthDay News) – For children from the Brazilian Amazon, FTO rs9939609 allele is associated with increased body mass index (BMI) and BMI-for-age Z scores, with the effect significantly modified by vitamin D status, according to a study published online Oct. 15 in Diabetes.

In an effort to examine the effect of FTO rs9939609 on BMI and BMI-for-age Z score changes, Barbara H. Lourenço, from the University of São Paulo in Brazil, and colleagues conducted a population-based longitudinal study involving 796 children from the Brazilian Amazon, aged younger than 10 years, who were followed for a median of 4.6 years.

The researchers found that, over follow-up, per rs9939609 risk allele there was a 0.07kg/m²/year increase in BMI and a 0.03Z/year increase in BMI-for-age Z scores (P=0.01). FTO effects were significantly modified by vitamin D status; among vitamin D insufficient (<75nmol/L) children, the rs9939609 allele correlated with a 0.05Z/year increase in BMI-for-age Z score; however, no significant genetic effects were noted for vitamin D sufficient children.

“In conclusion, FTO rs9939609 is positively associated with weight gain among children residing in the Brazilian Amazon,” the authors write. “We found evidence that vitamin D status might modify FTO genetic effects, which were more pronounced among children with insufficient vitamin D levels.”

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