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A groundbreaking study led by University College London reveals that a mother’s genes may have a stronger influence on a child’s risk of obesity than the father’s genes. Analyzing genetic and health data from over 2,600 UK families in the Millennium Cohort Study, the researchers tracked children from birth through age 17, examining how parental body mass index (BMI) and genetics impacted children’s weight, diet, and birthweight.
Using advanced genetic techniques called Mendelian Randomization with polygenic scores, the team distinguished between direct genetic inheritance and indirect effects, known as “genetic nurture.” These indirect effects mean that a parent’s genes can influence a child’s environment—through maternal eating habits, health during pregnancy, or family lifestyle—thereby affecting the child’s BMI beyond what is inherited.
While both maternal and paternal BMIs initially correlated with higher child BMI, adjustment for inherited genes left only the mother’s BMI showing a consistent association. Father’s BMI effects diminished significantly after genetics were accounted for, suggesting previous studies that linked fathers’ weight to children’s obesity may have overestimated paternal influence by conflating shared genes with environmental factors.
The findings support the “developmental overnutrition hypothesis,” which posits that high maternal BMI affects the fetus by exposing it to elevated glucose, fatty acids, and inflammatory signals in the womb, potentially altering appetite regulation and fat storage permanently. Notably, children of mothers with higher BMI had higher birthweights irrespective of genetics, a pattern not seen with paternal data.
Beyond weight, the study found maternal BMI linked to poorer diets in children, particularly during adolescence, including more fast food and sugary drink consumption and less fruit intake. These effects persisted even after separating direct inherited effects. Paternal BMI showed almost no consistent influence on children’s dietary habits.
The study highlights that maternal genetics not only contribute to inherited obesity risk but also shape the developmental environment, influencing the child’s long-term health trajectory. Indirect genetic effects from mothers ranged between 20% and 50% of direct genetic effects, and sometimes even exceeded the child’s own genetic influence on diet.
Dr. Liam Wright, lead author, emphasized that the findings are not about blaming mothers but supporting families with targeted health programs, especially during pregnancy, to reduce intergenerational obesity risks. These interventions could offer benefits for children immediate and lifelong.
As childhood obesity rates climb globally, this research underscores the need to focus on maternal health before and during pregnancy for effective prevention. It also challenges assumptions about the paternal role in childhood obesity, calling for genetically informed approaches in future studies.
The study was published in the journal PLOS Genetics.
Disclaimer: This article summarizes research findings and is not intended as medical advice. Individual health outcomes vary, and consultation with healthcare professionals is recommended for personal health concerns or decisions.
