Researchers have identified obesity as a significant driver behind rising cancer rates in adults under 50, according to a new study published in BMJ Oncology. The study found that 11 types of cancer are increasing in the 20 to 49 age group, with excess weight playing a crucial role.
Key Findings
The 11 cancers on the rise include thyroid, multiple myeloma, liver, kidney, gallbladder, colorectal, pancreatic, endometrial, oral, breast, and ovarian cancers. All except oral cancer are known to be linked to excess weight. The research, conducted by experts at the Institute of Cancer Research, London (ICR) and Imperial College London, suggests that obesity may contribute through elevated insulin levels and inflammation.
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 compares with 244,000 cases in the 50 to 79 age group, where the rate was about one in 100.
Bowel and Ovarian Cancer Trends
Bowel and ovarian cancer were exceptions, rising only in younger age groups. 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. However, the overall number of BMI-linked bowel cancer cases in younger women remained lower, indicating other contributing factors.
Unexplained Rise
Professor Montse García-Closas from the ICR noted that while BMI is the best clue, much of the increase remains unexplained. She estimated that around 15% of bowel cancer in younger people could be due to overweight or obesity, with 40% to 50% attributable to combined known risk factors such as obesity, lack of exercise, alcohol, and smoking.
The study found that most established risk factors—including smoking, alcohol consumption, red or processed meat intake, low fibre diets, and lack of exercise—remained stable or declined in the period leading up to diagnosis. This suggests these traditional factors do not substantially account for the rise.
Role of Obesity
In contrast, overweight and obesity have increased steadily since 1995. Between 2001 and 2019, around 20% of the increase in bowel cancer was explained by rising BMI. Professor Marc Gunter from Imperial College London highlighted that obesity is a known risk factor for 19 different cancers, partly due to higher insulin levels and inflammation.
The researchers called for large, long-term studies to identify all biological and environmental factors driving the trend. They emphasised 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.
Expert Reactions
Professor Amy Berrington from the ICR noted that while rates have increased, cancer in young people remains rare. Michelle Mitchell, chief executive of Cancer Research UK, stressed the need for more research but also highlighted the importance of government action, including restrictions on junk food advertising and making nutritious food more accessible.
She added that smoking remains a leading cause of cancer in adults under 50, and the recent Tobacco and Vapes Bill is a historic step. However, tackling obesity across all ages must become a national priority to slow the rise in cancer.
