Genetic determinants have an impact on adult weight but the association between genetic determinants and weight at young age is still poorly understood.

The objective of this study was to examine the association between genetic risk scores and early growth from birth to 2 years of age.

Genetic risk scores of 83 adiposity-related or obesity-related single nucleotide polymorphisms (SNPs) (genetic risk score [GRS]83) were calculated for 1278 children. Specific phenotype score for 16 weight-related SNPs (weightGRS) was calculated. Anthropometric data were obtained at birth, 13 months and 2 years of age.

The GRS83 was associated with weight at 13 months (β = 0.080, P = 0.015) and 2 years (β = 0.080, P = 0.017) of age and with weight gain from birth to 13 months (β = 0.069, P = 0.036) and to 2 years of age (β = 0.074, P = 0.028). At 2 years of age, the GRS83 was also associated with weight for height (β = 0.065, P = 0.046), weight-for-height standard deviation score (SDS) (β = 0.074, P = 0.022) and body mass index SDS (β = 0.068, P = 0.045). WeightGRS was associated with higher body weight at 13 months (β = 0.081, P = 0.014) and 2 years of age (β = 0.086, P = 0.011). The genetic effect on weight varied from 0.69 to 1.89 kg at 2 years of age according to number of risk alleles. Children with high genetic risk for adiposity were heavier than children with low genetic risk at 2 years of age (12.8 vs. 13.4 kg, P = 0.017).

The GRS 83 revealed increased genetic risk for higher weight in children already at 13 months and 2 years of age, which may result in increased obesity risk later in life.