Editorial NexoScience
Fewer young adults in England smoke than did a generation ago. They drink less and eat far less red meat. And yet more of them are getting cancer. That mismatch sits at the heart of a new analysis of national records, which asked a blunt question: can the usual lifestyle suspects explain why cancer is rising in young adults? For most of them, the answer is no.
The work, led by Montserrat García-Closas and Amy Berrington de González and published in the journal BMJ Oncology, tracked cancer diagnoses in England from 2001 to 2019. Among adults aged 20 to 49, rates climbed for 16 of the 22 cancer types studied in women and for 11 of 21 in men. The researchers then lined those curves up against two decades of national health surveys on smoking, alcohol, diet, body weight and exercise. Only one risk factor moved in the wrong direction over that time: excess body weight. Even that one, the authors concluded, can’t account for the whole increase.
Eleven cancers came under the spotlight. The team focused on cancers that were rising in younger adults and that already have well-established behavioural risk factors. That left thyroid, liver, kidney, gallbladder, colorectal (bowel), pancreatic, endometrial (the lining of the womb), oral, breast and ovarian cancers, plus multiple myeloma, a cancer of the plasma cells in bone marrow. Ten of the eleven are linked to obesity. Mouth cancer is the exception.
Bowel and ovarian cancer broke the pattern. Most of the eleven were rising in people over 50 too, often at a similar pace. That points to shared causes acting across ages. Two cancers didn’t fit. Colorectal cancer rose in younger adults while staying flat in older ones, and ovarian cancer rose in younger women while falling by about 1.3% a year in older women. Several others, including endometrial, kidney, pancreatic and thyroid cancers and multiple myeloma, rose faster in younger women than in older women. In men, only multiple myeloma showed that faster climb in the younger group.
The habits mostly got better. Smoking prevalence among younger adults has fallen by roughly 2% a year, in relative terms, since 1995. Heavy and moderate drinking declined after 2011. The sharpest change was on the plate. Between 2008 and 2018, the typical younger man went from about 38 grams of red meat a day to 17 grams, from roughly a small burger patty’s worth to less than half of that. Younger women cut theirs from 22 grams to 10. Fibre stayed a weak spot, with more than nine in ten younger adults falling short in 2018, but that figure didn’t get worse. If these habits were driving the rise, the numbers should have gone the other way.
Weight is the one factor that kept climbing. Obesity rose steadily from 1995 in every adult group, and fastest in younger women, at about 2.6% a year in relative terms. By 2019, roughly three in ten younger women were obese, compared with 23% of younger men. The rise was steeper in the most deprived parts of England than in the least deprived, and smoking fell more slowly there too. So the burden of the one worsening factor isn’t spread evenly.
Known risk factors still explain a large share of cases. This is the part that’s easy to lose. The analysis estimated the “population attributable fraction,” the share of cases in a population that can be tied to a given exposure. Depending on the cancer, it ranged from 7% to 65% in younger adults. For colorectal cancer, smoking, drinking, diet, inactivity and weight together accounted for about half of cases in younger men and nearly four in ten in younger women. Body weight on its own ranged from 5% of ovarian cancers to 37% of endometrial cancers. In other words, these factors matter a great deal for how much cancer there is. They just don’t explain why there’s more of it now.
Even with weight stripped out, rates still went up. Here’s the thing that makes the study stand out. The researchers split each cancer’s incidence into two parts: cases attributable to body mass index (BMI) and cases that aren’t. If obesity were the whole story, the second part should have stayed flat. It didn’t. For colorectal cancer in younger women, the BMI-linked portion grew by about 4.3% a year, but the portion with no link to weight still grew by 3.2% a year. Endometrial cancer showed the same shape, 3.8% a year against 1.7%. Weight speeds things up. Something else is pushing too.
The newer suspects don’t fit neatly either. The authors also checked exposures that have been floated as culprits for early-onset cancer. Ultra-processed food makes up a large share of what people in the UK eat, about 63% of energy intake in 2019, but that share has been flat or slightly falling. Sugary drink consumption dropped sharply between 2008 and 2016. Air pollution has fallen for decades, and antibiotic prescriptions have declined since 2006. Childhood obesity is the exception, rising from 17.5% to 22.7% among 10- and 11-year-olds between 2006 and 2023. Honestly, the list of candidates that actually got worse is short. The authors point to the gut microbiome as worth closer study, citing earlier work that found a DNA damage pattern in colorectal tumours linked to colibactin, a toxin made by some gut bacteria, which was more common in early-onset cases.
These are trends, not causes. The study is descriptive and ecological, meaning it compares population averages over time rather than following individuals, and the authors state plainly that it can’t establish cause and effect. It assumed a 10-year gap between exposure and diagnosis, and if the real delay is longer, the effect of weight could be underestimated. Some survey data were thin: physical inactivity was measured at only five time points between 2003 and 2012. Surveys rely on self-reporting, which tends to understate drinking and overstate exercise. Changes in screening and diagnosis may also play a part, and the authors note evidence of possible overdiagnosis for some of the cancers that rose, including thyroid, kidney and breast. The bowel screening programme for older adults, introduced in the mid-2000s, may help explain part of the age gap in colorectal cancer, though rates already differed before it started. And the analysis covers England only.
The bigger burden is still in older adults. For nearly every cancer studied, rates remain much higher after 50 than before it, with thyroid cancer the main exception. The authors argue that this is a reason to keep studying risk across all ages, while giving special attention to cancers like colorectal, whose rise is confined to younger generations and hints at something in early life. Their next questions are about exposures in childhood and even before birth, how several weak factors might add up, and how much of the increase reflects cancers simply being found more often. For now, the most solid conclusion is a negative one: the familiar list of lifestyle risks, weight aside, isn’t what’s behind the rise.
Source: García-Closas, M., Richards, Z., Frost, R., Gunter, M. J., Berrington de González, A. “Temporal trends in behavioural risk factors for cancers with rising incidence in younger adults: an analysis of population-based data in England.” BMJ Oncology (2026). DOI: 10.1136/bmjonc-2025-000966
This article summarizes published scientific research for general information. It is not medical advice and does not replace consultation with a qualified health professional.
