Having a high body mass index (BMI) as a young child may not reflect a lifelong risk of obesity, researchers suggest.
A study by experts in Australia found the genetic factors that influence the size of babies may be different to the ones that influence body size as a teenager.
The analysis used data of 6,291 youngsters who took part in the Children of the 90s study, based at the University of Bristol in Britain.
The team used modelling to explore how genetics contributes to the differences in how children’s body weight changes from ages one to 18.
The study found that the influence is low – at around a quarter.
Study lead author and University of Queensland Institute for Molecular Bioscience postdoctoral research fellow Dr Wang Geng said: “Parents often worry when a child gains weight early or grows differently from others, but our findings suggest that genetic variation can influence these changes.
“We found genetic factors that contribute to an infant’s body size may be different from the ones contributing to a teenager’s body size.
“When using these results to consider health, our results suggested body size differences in younger children don’t necessarily reflect lifelong obesity risk.”
Meanwhile, the study suggests that BMI around the age of 10, as well as the overall growth rate from one to 18 years, may be worth paying attention to as this is more likely linked to diabetes, high cholesterol and heart disease in later life.
Study corresponding author and Institute for Molecular Bioscience NHMRC Emerging Leadership Fellow Dr Nicole Warrington said the findings, published in the journal Nature Communications, show that “we are ignoring important information when assessing growth based on population averages”.
She added: “Future research is needed to help identify the most effective ages to prevent obesity or poor growth for long-term benefit.”
Children of the 90s principal investigator Prof Dr Nicholas Timpson said: “This work has suggested important genetic relationships with the way BMI changes from one to 18 years old, as well as average levels at any given age.
“The results here really do help us to get a better feel for the changing patterns and implications of health-related factors - like body size - as they vary across the life course.”
One in 10 children in the first year of primary school in England is obese.
Data from the UK National Child Measurement Programme shows 10.5% of children in Reception (the bridging year between Nursery and Year One in the British education system) and more than a fifth in Year Six were obese in 2024/25.
Boys were more likely to be overweight than girls.
Excluding the peak during the first year of the Covid-19 pandemic, this is the highest obesity prevalence seen in Reception year since records began in 2006/07, and is higher than the 9.6% in 2023/24.
Some 13% of children in Reception are also overweight. – PA Media/dpa
