Variation in the fat mass and obesity‐related ( FTO ) genotype is not associated with body fatness in infants, but possibly with their length

BACKGROUND: Data relating variation at the fat mass and obesity-related (FTO) locus (rs9939609) to fat mass in infancy are inconclusive. OBJECTIVE: To study relationships between FTO genotype and infant size (at 1 and 12 weeks and at 1 year of age) and body composition (at 1 and 12 weeks). METHODS: Body composition was assessed using air displacement plethysmography in 207 infants. FTO was genotyped using the TaqMan assay. RESULTS: The number of risk alleles was related to length at 1 and 12 weeks (P = 0.007-0.033) but not to fat mass. The relationship to length was stronger in boys than in girls. CONCLUSIONS: Our results suggest that the FTO genotype is not related during infancy to fat mass but is related to length in boys but not in girls.