UK study finds clue to rising cancer rates in younger people

A study has found evidence that 11 cancers are becoming more common among young people in England, and points to a main driving factor – although it is unlikely to be the only cause.

The research by scientists at the Institute of Cancer Research and Imperial College London found that being overweight or obese is the most likely driver for rising rates of cancer in the under-50s over the last two decades.

Rising average body mass index (BMI) scores outweighed other risk factors like smoking, alcohol use, red or processed meats, low fibre intake, and physical inactivity, which have been stable or trending down over the same period.

However, the study in BMJ Oncology suggests that increases in BMI alone are not sufficient to explain the overall rise in cancer incidence, which the researchers said points to "additional, suspected, or currently unknown causes." The largest increases in obesity were seen in younger women, with a 2.6% relative increase per year since 1995.

Overall, obesity and being overweight were linked to 10 of the 11 cancers that have been rising among younger people, including bowel, pancreatic, endometrial, breast, ovarian, and liver cancers, with oral cancer the only one bucking that trend.

For most of these cancers, increases in younger adults mirrored trends in people over 50 – where the overall disease burden is much higher – but bowel cancer and ovarian cancer were notable exceptions, rising only in younger age groups.

A look at the results for bowel cancer explains why the researchers think factors other than rising BMIs must be involved, with only around a fifth of cases in younger people attributable to their BMI. The researchers speculate that other variables not captured in their study – such as metabolic dysfunction, inflammation, and gut microbiomes – may be involved.

"Our findings show that, while cancer rates are rising in younger adults, the trends are unlikely to be explained by changes in most known behavioural risk factors," said ICR's Prof Montserrat Garcia-Closas, one of the study investigators.

"Excess weight is an important contributor, although it cannot fully account for the scale of the rise in bowel and other cancers," she added. "This tells us that multiple factors – including early‑life exposures – may be acting together. Understanding these patterns is essential for identifying what is truly driving cancer risk in today's generations."

ICL's Prof Marc Gunter said the results reflect "a complex mix of generational effects, gaps in long‑term exposure data, and shifts in diagnosis and detection, and show how much more scientists still need to understand about when and how cancer develops across the life course."

Around one in 1,000 people aged from 20 to 49 get a cancer diagnosis each year, with the rate rising to one in 100 for those aged over 50.