Nearly half of all cancer cases are linked to obesity

Study finds excess weight could be fuelling more than 30 types of obesity. Photo / 123RF

Nearly half of all cancer cases are linked to obesity, new research has found.

The study of more than four million adults, who were tracked for decades, found excess weight could be fuelling more than 30 types of the disease.

Experts said the findings, which will be presented at the European Congress on Obesity in Venice, were “groundbreaking”, showing a timebomb ahead.

Health charities urged ministers to act on the “wake-up call,” with obesity already estimated to cost the country almost £100 billion (NZ$208 billion) a year, including £19 billion in NHS costs.

Victoria Atkins, the Health Secretary, said the Government was taking “strong action” to tackle obesity, with a drive to harness apps and technology to overhaul lifestyles expected this summer.

“I want us all to be able to lead longer, healthier lives,” she said.

The study led by Lund University in Malmo, Sweden, involved 4.1 million participants who were monitored for about 40 years, with close monitoring of their weight and lifestyle.

Over the period, 332,500 cancers were identified. In 40 per cent of cases, there appeared to be a link between excess weight and the development of cancer.

There are an average of 390,000 cancer diagnoses in the UK annually, meaning that around 150,000 of them could be linked to obesity.

In total, researchers identified 32 types of cancer with an obesity link.

Previously, international research had identified 13 types of cancer that were linked to being overweight or obese, including bowel, breast, womb and kidney. The new study found that a five-point increase in Body Mass Index (BMI) appeared to increase the risks of such cancers by 24 per cent for men and 12 per cent for women.

The same increase – enough to take someone from the threshold for healthy weight to the cusp of obesity – was linked to 19 other cancers, with the risk raised by 17 per cent for men and 13 per cent for women. These cancers include malignant melanoma, gastric tumours, cancers of the small intestine and pituitary glands, as well as types of head and neck cancer, vulval and penis cancer.

Researchers identified 32 types of cancer with an obesity link. Photo / 123RF

In total, researchers examined 122 types and subtypes of cancer in a study that tracked patients over 100 million years of follow-up.

“The findings of this study have important public health implications. Established obesity-related cancers accounted for 25 per cent of all cancer cases in this study, and the proportion increased to 40 per cent when potential obesity-related cancers were added. Therefore, a substantial proportion of cancers could potentially be prevented by keeping a normal weight,” researchers said.

Obesity rates have almost doubled in the UK since the 1990s, with 26 per cent of adults in England now classed as obese, while 38 per cent are overweight.

Obesity overtakes smoking as leading cause of four cancers

Obesity has overtaken smoking as the leading cause of four major cancers, with smoking now the cause of one in five cases of cancer.

Forecasts from Cancer Research UK say that around 8000 cancer cases in England could be avoided by 2040 if 10 per cent of those who are overweight and obese shift down one BMI category by 2030.

Professor Jason Halford, president of the European Association for the Study of Obesity (Easo) said: “This is a really strong, large-scale analysis. As always, more research is needed but it reveals what many studying the links between cancer and obesity have suspected; that obesity is likely to be a risk factor for many more types of cancer than we had evidence for before.”

Prof Halford, head of the School of Psychology at the University of Leeds, accused policymakers of a “clear failure” to take strong public measures to prevent obesity, while limiting treatment options.

“If this does not cause concern for health policy makers it is difficult to see what will,” he said.

The study led by Lund University in Malmo, Sweden, involved 4.1 million participants who were monitored for about 40 years. Photo / Getty Images

The Health Secretary is expected to set out Government plans to help people overhaul unhealthy lifestyles in the summer, with a focus on the use of apps and new technology to monitor step counts and take more control of health.

The NHS is also piloting schemes to expand the use of weight loss jabs such as Wegovy, which is the same medicine as the drug Ozempic, which is used to treat Type 2 diabetes.

Atkins said: “I want us all to be able to lead longer, healthier lives. That starts with preventing illness through healthy lifestyle choices, like eating well, exercising regularly and not smoking.

“We are already introducing world-leading legislation to protect future generations from the harmful effects of smoking to reduce illnesses like cancer, and we’re taking strong action to tackle obesity too.

“By investing in tech like the NHS Couch to 5k app, we are helping families all over the country get fit and active, and I am excited about the new treatments and technologies that can help people achieve – and maintain – a healthy weight.”

Katharine Jenner, director of the Obesity Health Alliance – a coalition of 50 health charities and organisations, said: “The results are clear – if we can prevent obesity, we can prevent many types of diet-related cancers.

“This should be a wakeup call to the UK Government and governments around the world, to urgently implement public health policies which will make a meaningful difference, such as restrictions on junk food marketing, and levies on unhealthy food. We need to make the healthy choice the easy choice for everyone.”

Lead researcher Dr Ming Sun, from Lund University, said: “Our findings suggest that the impact of obesity on cancer might be greater than previously known, in that it is a risk factor for more cancers, especially of rarer kind. Some of these have rarely or never before been investigated in relation to obesity.”

The UK's National Health Service is piloting schemes to expand the use of weight loss jabs such as Wegovy, which is the same medicine as the drug Ozempic. Photo / AP

He said further investigation to replicate the findings and investigate the underlying biological mechanisms was warranted.

But Dr Sun said public health measures to overhaul lifestyles were “essential to address the obesity epidemic and its already known detrimental effect on health outcomes”.

Dr Jennifer L Baker, co-chairman of EASO’s childhood obesity working group, said the increased obesity risk might be explained by biological mechanisms such as chronic inflammation and changes to metabolism and hormone levels, while extra weight could render screening programmes less effective.

Dr Baker said: “In this groundbreaking study, using an extremely large population of Swedish adults, researchers show that obesity is associated with 19 new cancer forms, some of which are surprising, in addition to the 13 that have already been identified.”

“These new results show we are likely facing a significant increase in cancer cases,” she said.

Malcolm Clark, Cancer Research UK’s senior prevention policy manager, said: “There are lots of things people can do to lower their risk of cancer, and keeping a healthy weight is one way to reduce it. Other steps include not smoking, being safe in the sun, eating a healthy balanced diet and cutting down on alcohol.”

Ministers have repeatedly promised to introduce a TV and online ban on advertising junk food but restrictions have been pushed back and are currently planned for October 2025.