Pregnant Woman Group In Row. Young Mothers [AndreyPopov/ iStock/ Getty Images Plus]
A mother’s genes may be particularly important in determining the body mass index (BMI) of her children, research suggests, with both direct genetic and nurturing effects coming into play.
By contrast, the findings in PLOS Genetics suggested that fathers’ genetic makeup had little impact on their child’s BMI outside the genes that they directly pass on.
“Our results suggest mother’s weight could affect their children’s weight; policies to reduce obesity could have intergenerational benefits,” the authors, led by Liam Wright, PhD, from University College London, asserted in a press statement.
Obesity has risen dramatically among children in recent decades, and the role of parents in this is a focus of research. Obese children are likely to have parents that are also obese, and several reasons have been proposed behind this outside genetic inheritance.
One of these in the developmental overnutrition hypothesis, which proposes that higher levels of adiposity in the mother while the child is in utero can have long-term effects on the child’s BMI by increasing circulating maternal levels of pro-inflammatory cytokines, glucose, and fatty acids.
Diet and physical activity in the family environment as the child grows up could also have an impact, as could food availability and behavior modeling.
The team measured whether maternal and paternal obesity-related genes were associated with their child’s adiposity and diet after accounting for direct genetic inheritance by performing a Mendelian Randomization analysis of over 2,600 mother-father-child trios.
The data came from the Millennium Cohort Study, a U.K. birth cohort with repeat assessment of children’s BMI and diet from early childhood to late adolescence.
The team found that the BMI of mothers and fathers consistently correlated with that of their child, but that this could be mostly explained through directly inherited genes.
After accounting for direct genetic inheritance, there was only evidence for maternal genes operating indirectly through maternal traits, and then only during the child’s adolescence.
These had less of an impact, with indirect genetic effects estimated to be between 20–50% of the direct genetic effects for the child’s BMI.
Alternative measures of adiposity, such as fat mass and waist- to-height ratio, showed positive but imprecise associations with maternal BMI after accounting for genetic inheritance.
There was weak evidence of an association between the mother’s BMI and child’s diet, at least at ages 14 and 17 years old, and again when direct genetic inheritance was accounted for.
“Results suggest maternal BMI may be particularly important for offspring BMI: associations may arise due to both direct transmission of genetic effects and indirect (genetic nurture) effects,” the researchers concluded.
“Associations of father’s and offspring adiposity that do not account for direct genetic inheritance may yield biased estimates of paternal influence.”