A new study has identified obesity as a significant driver behind rising rates of 11 types of cancer among adults under the age of 50. Researchers from the Institute of Cancer Research, London (ICR) and Imperial College London analysed national cancer registry data for England from 2001 to 2019, revealing that cancers including thyroid, multiple myeloma, liver, kidney, gallbladder, colorectal, pancreatic, endometrial, oral, breast, and ovarian are increasing in the 20 to 49 age group.
Obesity as a Key Factor
All of the 11 cancers identified, except oral cancer, are known to be linked to excess weight. The researchers suggest that being overweight or obese may play a crucial role, potentially due to elevated levels of insulin and inflammation. While they caution that obesity does not fully explain the trend and further evidence is required, the findings highlight a pressing public health concern.
In England, approximately 31,000 cancers were diagnosed in people aged 20 to 49 in 2023, equating to roughly one in every 1,000 individuals. This contrasts with 244,000 cases diagnosed in the 50 to 79 age group, where the rate was about one in 100. For nine of the 11 cancers, rates are increasing in both younger and older adults, but bowel and ovarian cancers are rising only in younger age groups.
Bowel Cancer Trends
The study found that bowel cancer rates in younger women linked to body mass index (BMI) rose faster (from 0.9 to 1.6 per 100,000 people) than those not linked to BMI (from 6.4 to 9.6 per 100,000 people). Similar patterns were recorded for men. However, the overall number of BMI-linked bowel cancer cases in younger women remained lower than non-BMI-linked cases, suggesting other factors must be contributing to the increase.
Other Potential Causes
Several suspected contributors, including ultra-processed foods, antibiotic use, and air pollution, have been proposed in recent years. However, many of these factors have shown stable or declining trends in the UK, reinforcing the need to thoroughly examine all reasons. The researchers call for large, long-term studies to identify all biological and environmental factors behind the rise.
Professor Montse García-Closas from the ICR said more research is needed, but “we cannot wait to act.” She noted that data suggest around 15 per cent of bowel cancer in younger people could be due to being overweight or obese, with 40 to 50 per cent attributable to combined known risk factors such as obesity, lack of exercise, alcohol, and smoking.
Insulin and Inflammation
Professor Marc Gunter from Imperial explained 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 said. “Insulin is a growth factor and has been linked to cancer.”
Public Health Priority
The researchers emphasised that tackling obesity across all ages, particularly in children and young people, must become a national priority. Stronger public health policies and wider access to effective interventions could slow the rise in cancer and prevent many cases.
Michelle Mitchell, Cancer Research UK’s chief executive, commented: “Globally, and in the UK, we’re seeing a small increase in cancer rates in adults under 50. The picture is complex and we need more research to understand what’s driving the trend, but this study helps to fill in some gaps. Overweight and obesity doesn’t explain the rise in full though. Improvements in detection are likely to also be playing a part, meaning that more people are being diagnosed at a younger age.”
She added that smoking remains a leading cause of cancer in adults under 50, and measures to restrict advertising and promotion of junk food, along with making nutritious food more accessible, could help people maintain a healthy weight.
