A significant new study has revealed that eleven types of cancer are becoming more prevalent among individuals aged 20 to 49. The cancers identified include bowel, breast, ovarian, liver, kidney, gallbladder, pancreatic, thyroid, multiple myeloma, endometrial, and oral cancers. Researchers note that all but oral cancer are associated with obesity, potentially due to elevated insulin levels and inflammation.
Obesity as a Contributing Factor
Professor Montse Garcia-Closas from the Institute of Cancer Research (ICR) in London emphasised the urgency of addressing obesity. "Tackling obesity across all ages, particularly in children and young people, through stronger public health policies and wider access to effective interventions, could slow the rise in cancer and prevent many cancers - and must become a national priority," she stated.
The study, conducted by experts at the ICR and Imperial College London and published in BMJ Oncology, analysed cancer registry data from England between 2001 and 2019. While rates of several cancers have increased in younger adults over the past two decades, most known risk factors—such as smoking, alcohol consumption, red or processed meat intake, low fibre consumption, and physical inactivity—have remained stable or declined. This suggests these factors are unlikely to be the primary drivers of the increase.
BMI Trends and Cancer Incidence
In contrast, overweight and obesity rates have risen steadily since 1995, making them plausible contributors. However, the researchers found that increases in body mass index alone cannot fully explain the overall rise in cancer among younger adults in England. Other factors, whether suspected or unknown, must also be at play.
For nine of the 11 cancers, rates are increasing in both younger and older adults, though older individuals remain at higher risk. Bowel and ovarian cancers are exceptions, rising only in younger age groups. Specifically, bowel cancer rates in younger women linked to BMI increased from 0.9 to 1.6 per 100,000 people, while those not linked to BMI rose from 6.4 to 9.6 per 100,000. Similar patterns were observed in men. The overall number of BMI-linked bowel cancer cases in younger women remains lower than non-BMI-linked cases, indicating additional contributing factors.
Potential Additional Causes
Several suspected contributors, including ultraprocessed foods, antibiotic use, and air pollution, have been proposed in recent years. However, many of these factors have also shown stable or declining trends in the UK, reinforcing the need for comprehensive investigation into all possible causes.
In 2023, approximately 31,000 cancers were diagnosed in people aged 20 to 49 in England, roughly one in 1,000 individuals. In contrast, 244,000 cases were diagnosed in those aged 50 to 79, about one in 100. Among the younger group, breast cancer was most common (8,500 cases), followed by bowel cancer (3,000 cases) and melanoma (2,800 cases).
Expert Insights
Professor Garcia-Closas noted that around 15% of bowel cancer in younger people could be attributed to being overweight or obese, with 40% to 50% linked to combined known risk factors such as obesity, lack of exercise, alcohol, and smoking. "Our main conclusion is that although BMI is our best clue, much of the increase still remains unexplained," she said. "It's likely a combination of multiple factors that act together."
The team estimated that between 2001 and 2019, about 20% of the increase in bowel cancer was explained by rising BMI levels. Professor Amy Berrington from the ICR remarked, "Although rates have been increasing, cancer in young people is still a rare disease." Professor Marc Gunter from Imperial College added that obesity is a known risk factor for around 19 different cancers. "For some of these cancers, including colorectal cancer, we think this could be partly caused by higher levels of hormones such as insulin, which is often elevated in people with obesity, as well as inflammation," he explained.
The researchers are calling for large, long-term studies to identify all biological and environmental factors contributing to rising cancer rates in young adults. Nonetheless, they argue that the evidence on obesity is strong enough to make it a public health priority, particularly in reducing obesity rates among children and young people.
