OBESITY does get passed down through families, but one parent's genes may play a bigger role in children's weight, scientists say.
UCL researchers looked at the body mass index (BMI), diet and genetic data of over 2,500 families.
They found that kids whose parents were obese were more likely to be obese themselves.
But children's weight was more heavily impacted by the genes of a specific parent.
A mum's genetics may play a bigger role in determining whether a child becomes overweight than a dad’s - even if those genes aren't passed down.
Lead author Dr Liam Wright, from the UCL Social Research Institute, said: “Mothers’ genetics appear to play an important role in influencing her child’s weight over and above the child’s genetics.
“In addition to the genes mums directly pass on, our findings suggest that maternal genetics are instrumental in shaping the environment in which the child develops, therefore indirectly influencing the child’s BMI too.”
Published in PLOS Genetics, the study analysed genetic and health data from 2,621 UK families.
Researchers investigated how parents’ BMI and related genes influenced their children’s weight and diet from birth to age 17.
To do this, the team looked at the kids' weight, BMI, and diet at six key points during childhood and adolescence, at the ages of three, five, seven, 11, 14, and 17.
They focused on how these were linked to the parents' BMIs.
Children’s diets were assessed through self-reported records of how often and how much they consumed different food groups, including fruit, vegetables, fast food, and sugary drinks.
By measuring both children’s and their parents’ genes, the researchers were able to separate how inherited genes affected the kids, versus the indirect effect of genes that were not inherited.
Non-inherited genes can still influence children’s outcomes by influencing their development environment, researchers explained.
For example, conditions that babies are exposed to in the womb and parenting techniques can all be shaped by parents' genes.
Researchers found that both parents’ BMI was linked to their child’s BMI.
But a dad's influence could mostly be attributed to direct genetic inheritance.
Meanwhile, a child didn't need to inherit their mum's genes for their weight to be influenced by hers.
For example, a mum’s genes might influence her own weight, eating habits, or behaviours during pregnancy, which in turn affect her child’s development and long-term health.
This suggests, that genetic nurture - where a parent’s genes shape the environment they create for their child - is a big factor in children's weight, researchers said.
Dr Wright stressed: “This isn’t about blaming mothers, rather, supporting families to make a meaningful difference to children’s long-term health.
“Targeted interventions to reduce maternal BMI, particularly during pregnancy, could reduce the intergenerational impacts of obesity."
Childhood obesity is a continuing problem in the UK - as well as other countries - with NHS data from 2024 showing 27 per cent of children aged between two and 15 were either obese or overweight.
Excess weight raises the risk of people suffering cancer, dementia, heart disease, stroke, type 2 diabetes, and liver and kidney disease.
Researchers from the University of Washington predicted that without urgent action, six in ten adults and a third of youngsters worldwide will be overweight or obese in 25 years.
