Increasing obesity rates linked to surge in cancer deaths

A recent US study has shown how a sharp rise in obesity has driven a threefold increase in deaths from cancers linked to excess weight.

An analysis of over 33,000 cancer deaths in the United States between the late 1990s and 2020 revealed a stark rise in fatalities from obesity-related cancers – up from 3.7 per million people to 13.5 per million in just two decades. The findings were presented at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco.

The rise includes cancers of the bowel and colon, which are seeing an increase among younger adults under 50 – even those who appear otherwise healthy.

The analysis also showed that women, older adults, people in rural areas and individuals from Black and Native American backgrounds have been disproportionately affected by the increase in obesity-related cancer deaths.

Obesity is a known risk factor for 13 types of cancer, including bowel, breast, liver, pancreatic, uterine and kidney cancers. In the UK excess weight is now the second leading cause of cancer, responsible for one in 20 cases. In the US, obesity is linked to around 40 per cent of all cancer diagnoses each year.

Dr Faizan Ahmed, lead researcher from Hackensack Meridian Jersey Shore University Medical Centre, said the findings emphasise the urgent need for national strategies to combat obesity.

“This research underscores the need for targeted public health strategies such as early screening and improved access to care, especially in high-risk rural and underserved areas,” he said.

Excess body fat is believed to contribute to cancer in several ways, it increases levels of growth hormones that stimulate cell division, it triggers chronic inflammation, and, in postmenopausal women it raises levels of oestrogen – which increases the risk of breast and womb cancers.

Obesity rates have risen dramatically in recent decades. In England, around one in four adults is now living with obesity – double the rate in the 1990s. In the US, the figure has jumped from 12 per cent to 40 per cent.

While obesity is thought to be responsible for around 5 per cent of all UK cancer cases, it is linked to 11 per cent of bowel cancer diagnoses. Men are particularly at risk, with each additional 5kg of adult weight gain increasing bowel cancer risk by 10 per cent. For every five-point increase in BMI, a man’s colon cancer risk rises by 30 per cent; for women, the increase is 12 per cent.

Globally, cases of bowel cancer in under-50s are rising in more than half of countries studied – including England, where rates are increasing by 3.6 per cent annually among younger adults.

Although obesity plays a role, experts are also investigating other possible environmental causes for the rise in younger people. These include dietary chemicals, microplastics, pollution and even exposure to E. coli in food – although no single cause has been confirmed.

In the UK, around 2,600 people aged 25–49 are diagnosed with bowel cancer each year, alongside roughly 44,000 across all ages. The disease causes nearly 17,000 deaths annually in Britain and around 50,000 in the US. Just over half of those diagnosed survive for at least 10 years after diagnosis.