To evaluate if percentile-specific effects of genetic, environmental and lifestyle obesity risk factors on body mass index (BMI) might reflect gene-environment interactions with respect to the development of overweight.

Design and Methods

Retrospective study with data of 2,346 children from the Avon Longitudinal Study of Parents and Children (ALSPAC), using quantile regression with body fat mass index (FMI) for children at the age of 9 years as outcome variable. We assessed interactions of an “obesity-risk-allele-score” with environmental and nutritional factors.


There was no evidence of interactions between the obesity-risk-allele score and the environmental variables except for maternal overweight. However, we found a significant interaction with respect to intake of mono- and polyunsaturated fatty acids at the age of 7. In children with low intake, genetic risk was associated with increasing effect sizes by FMI percentile.


Our results suggest an interaction between a low dietary content of unsaturated fatty acids and genetic risk factors for overweight on FMI. This effect is likely to be stronger in children with higher FMI.