Obesity is a key factor for the rising rates of cancer among younger people in England, according to a study.

There are 11 types of cancer, including bowel and ovarian cancer, that are increasing among people aged 20 to 49 between 2001 and 2019, according to analysis by researchers from the Institute of Cancer Research and Imperial College London.

Obesity is the only known behavioural risk factor that has been increasing in younger adults over this period, while more established risks such as smoking, alcohol, red meat and physical inactivity have all remained stable or in decline in England.

This led researchers to conclude that the increase in obesity was a key factor behind the rising rate of cancer cases. Excess weight was associated with 10 of the cancers identified, including thyroid, kidney and pancreatic cancer, with oral cancer being the only exception.

Maintaining a healthy weight could prevent about 20% of bowel cancers, 35% of endometrial cancers and 27% of kidney cancers, according to the researchers.

The study comes as recent figures revealed that the number of people in the UK being diagnosed with cancer has reached a record high, with one person diagnosed every 80 seconds and more than 403,000 people diagnosed each year.

Despite obesity being identified as a key risk factor behind the rising cancer rates among younger adults in England, researchers have said that it is not sufficient to explain the overall rise, indicating that there may also be unknown causes.

Prof Montserrat García-Closas, co-director of the Cancer Epidemiology and Prevention Research Unit and Group Leader in Integrative Cancer Epidemiology at the Institute of Cancer Research, said:“Excess weight is an important contributor, although it cannot fully account for the scale of the rise in bowel and other cancers. 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,” she said.

“However, we cannot wait to act. 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.”

The increase in cancer rates among younger adults also mirrored trends seen in people aged over 50, with the exception of bowel and ovarian cancer, which were only seen to rise among younger people by 3% and 0.7% a year on average respectively.

Michelle Mitchell, the chief executive of Cancer Research UK, said: “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.

“Preventing cancer cases must be a priority for the UK government. Measures to restrict the advertising and promotion of junk food, introducing mandatory reporting and targets on healthy food sales, and making nutritious food more accessible to everyone, would all help people keep a healthy weight.”