A new study suggests that boys who become overweight in their early teens risk damaging the genes of their future children, increasing their chances of developing asthma, obesity, and low lung function.

Research published this week in Communications Biology is the first human study to reveal the biological mechanism behind the impact of fathers' early teenage obesity on their children.

Researchers from the University of Southampton and the University of Bergen investigated the epigenetic profiles of 339 people, aged 7 to 51. They assessed the father's changes in body composition across adolescence using self-reported body image as a proxy for body fat composition.

The team identified epigenetic changes in more than 2,000 sites in 1,962 genes linked with adipogenesis (formation of fat cells) and lipid (fat) metabolism in the children of fathers who gained weight as teenagers.

These changes in the way DNA is packaged in cells (methylation) regulate gene expression (switching them on and off) and are associated with asthma, obesity, and lung function. The effect was more pronounced in female children than in male children, with different genes involved.

"The overweight status of future fathers during puberty was associated with a strong signal in their children's DNA, which was also related to the likelihood of their children being overweight themselves," says Dr. Negusse Tadesse Kitaba, senior research fellow at the University of Southampton.

"Early puberty, when boys start their developing sperm, seems to be a key window of vulnerability for lifestyle influences to drive epigenetic changes in future offspring."

Professor Cecilie Svanes from the University of Bergen states, "The new findings have significant implications for public health and may be a game-changer in public health intervention strategies."

"They suggest that a failure to address obesity in young teenagers today could damage the health of future generations, further entrenching health inequalities for decades to come."

Prof. John Holloway from the University of Southampton and the NIHR Southampton Biomedical Research Centre adds, "Childhood obesity is increasing globally. The results of this study demonstrate that this is a concern not only for the health of the population now but also for generations to come."