New Finnish research reveals that genetic predisposition to higher body weight in adolescence may accelerate biological ageing, with long-term health implications. The study highlights the importance of early weight management alongside lifestyle factors.
Researchers in Finland have found that teenagers with a stronger inherited tendency towards higher body weight showed signs of faster biological ageing that were still visible decades later, when many were in their 40s and 50s. The work adds to a growing body of evidence that chronological age and biological age do not always advance together: as Mayo Clinic Press explains, chronological age is simply time since birth, whereas biological age reflects how well the body’s systems are functioning.
The study, published in the International Journal of Obesity and based on the long-running Young Finns Study, followed participants from childhood into middle age and used blood samples to track chemical changes in DNA that act as so-called ageing clocks. According to the report, more than 2,000 people had at least one biological-age measurement taken, with assessments made in adolescence, again in adulthood, and later in mid-life. The analysis also used genetic risk scores to estimate whether DNA variants linked to higher body mass index, or BMI, were associated with faster ageing.
The central finding was that genetic risk for higher BMI was linked to quicker biological ageing across most of the measurements used, and that higher BMI during adolescence appeared to explain part of that relationship. In contrast, how fast weight increased during the teen years mattered less than entering adolescence already heavier. That pattern fits with broader medical explanations of biological ageing, which hold that genetics, lifestyle and environment all shape how quickly the body ages.
To test whether the association might be causal rather than merely correlated, the researchers used Mendelian randomisation, a genetic method that relies on inherited variants fixed at birth. Their strongest evidence pointed to a causal link between genetically predicted teenage BMI and faster ageing on one of the clocks used, although the result was less consistent with the other measure and with a genetic score based on childhood body size rather than adult BMI. The finding is broadly in line with earlier guidance from the Mayo Clinic Press that genetics are only part of the ageing story; lifestyle factors such as diet, activity, stress, smoking and alcohol use remain major influences.
The researchers noted that the share of participants who were overweight or obese rose sharply between the teenage years and their 40s, underscoring how early weight patterns can persist over time. While the study does not prove that every teenager with a higher BMI will age faster, it suggests that excess weight in adolescence may leave a long shadow on later health, particularly for those already genetically predisposed to higher body weight. For parents and caregivers, the practical message is that attention to weight and related health risks should begin early, alongside the more familiar advice to support healthy habits across childhood and adolescence.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
