New scientific research has revealed a powerful link between physical activity during the teenage years and a reduced risk of developing breast cancer later in life. The study, published in the journal Breast Cancer Research, provides compelling evidence that encouraging adolescent girls to stay active could be a crucial preventive health measure.
The Science Behind Activity and Risk
The analysis found that teenage girls who reported engaging in at least two hours of recreational physical activity in the previous week showed a lower percentage of water content in their breast tissue compared to those who were inactive. This is a significant finding because lower water content is associated with lower breast density, a well-established predictor of breast cancer risk.
Lead author Rebecca Kehm, an assistant professor at Columbia University, emphasised the urgency of the research. "The importance and urgency of this research are underscored by the rising incidence of breast cancer in young women and the alarmingly low levels of recreational physical activity observed both in this study and among adolescents across the United States and globally," she stated.
The study involved teenage participants with an average age of 16, who self-reported their activity levels and attended clinic visits. During these visits, researchers took blood and urine samples and assessed breast tissue composition. Alarmingly, more than half (51 per cent) of the participants reported doing no physical activity at all in the week prior.
Addressing Health Disparities in Research
A notable strength of the study was its focus on communities often left out of medical research. The majority of participants (64 per cent) were from Hispanic backgrounds, with Black communities also represented. Professor Kehm highlighted that these groups are "historically unrepresented in studies" but "face higher risks of developing breast cancer at younger ages."
She further explained a key behavioural disparity: "Black and Hispanic girls consistently report lower levels of recreational physical activity than their non-Hispanic white peers." This makes targeted interventions to promote exercise in these communities even more critical.
Aligning with Adult Studies and Expert Reaction
These new findings in adolescents align with existing research in adult women, which has shown that higher physical activity levels are connected to lower breast density. Previous studies indicated that the most active women had a 20 per cent lower risk of breast cancer compared to the least active.
Professor Jayant Vaidya from University College London (UCL), commenting on the study, told The Independent: "It is well known that physical activity reduces the risk of breast cancer... Also, the cancer-predisposing changes are likely to occur when breast tissues are maturing during adolescence and this could be the best time to take preventive action."
He added that the results are "interesting and should stimulate further research into early markers of risk and promote structured exercise early in life - which of course has many other benefits."
The research also connects physical activity to lower concentrations of stress-related biomarkers in urine, adding another potential pathway through which exercise may protect against cancer.
The UK Context and the Path Forward
The call for getting girls more active is particularly relevant in the UK. According to the Youth Sport Trust 2025 report, girls in the UK are over three times more likely than boys to dislike participating in PE classes, and twice as likely not to achieve an hour of daily physical activity.
This public health challenge exists against a stark backdrop: Breast cancer is the most common cancer in women in the UK. Charity Breast Cancer Now states that one in seven women will develop it in their lifetime, with over 55,000 women and 400 men diagnosed each year—equating to a woman being diagnosed every nine minutes.
While the authors note that more research is needed to determine exactly how adolescent factors impact long-term cancer risk, the study powerfully highlights the importance of promoting physical activity from a young age. Investing in girls' health and fitness during their developmental years could yield significant dividends for cancer prevention for decades to come.
