Rising obesity levels have led to a tripling of deaths from cancers linked to being overweight, American medics warn.
Analysing data from 33,000 obesity related cancer deaths in the US between the late 90s and 2020 the experts found the number of fatalities had risen from 3.7 per million to 13.5 per million across the two decades.
This included deaths from bowel and colon cancer, a form of the disease known to be mysteriously rising among young healthy adults under 50.
The analysis also found certain parts of the population had been harder hit by rising cancer deaths than others.
These included women, older adults, rural population and people from Black and Native American backgrounds.
Obesity is known to increase the risk of 13 types of cancer, with being overweight the second biggest cause of the disease in Britain triggering one in 20 cases.
In the US, cancers linked to obesity account for 40 per cent of all forms of the disease diagnosed per annum.
Dr Faizan Ahmed, of Hackensack Meridian Jersey Shore University Medical Centre in New Jersey and lead researcher of the analysis, said the findings showed the importance of public measures to tackle obesity.
Rising obesity levels have led to a tripling of deaths from cancers linked to being overweight, American medics warn
‘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.
The analysis also found the burden of obesity-related cancer deaths was higher in certain parts of the US.
Regionally the Midwest had the highest rates while the Northeast had the lowest.
By state level Vermont, Minnesota and Oklahoma had the highest rates of deaths, while Utah, Alabama and Virginia had the lowest.
Obesity increases the risk of 13 cancers: oesophageal, breast, bowel, uterus, gallbladder, stomach, kidneys, liver, ovaries, pancreas, the thyroid and one type of brain and blood cancer respectively.
Having extra fat on the body increases the risk of cancer in various ways.
Too much body fat can cause levels of growth hormones to increase. This in turn encourages cells to divide more often, and the risk of mutations that could become cancer.
Fat also causes inflammation in the body where it accumulates which also encourages cell division and increases the risk of cancer.
Finally—for women—fat cells can produce more of the female sex hormone oestrogen after menopause.
This can lead to increased cell division in the breasts and womb, increasing the risk of cancer developing.
About one in four people in England are obese, roughly double the proportion in the 90s.
The increase has been even starker in the US with 40 per cent now considered obese compared to about 12 per cent in the early 90s.
While obesity is thought to be responsible for about 5 per cent of all cancers in the UK, this dramatically increases for certain types.
For bowel cancer—which includes colon and rectal cancer—obesity or being overweight triggers 11 per cent of all cases of this disease.
Men are especially at risk with research suggesting a man’s risk of developing bowel cancer increases by 10 per cent for every 11lbs (5kg) he puts on in adulthood.
The risk of colon cancer in men increases by 30 per cent for every five increase of their body mass index (BMI).
For women the chances of developing colon cancer increases by 12 per cent for every five BMI they gain.
Experts have noted a concerning and mysterious rise in rates of bowel cancer among young adults, defined in cancer terms as those under 50.
A recent global study found rates of bowel cancer in under 50 year-olds are rising in 27 of 50 nations.
England is averaging a 3.6 per cent rise in younger adults every year-one of the highest increases recorded.
While the disease is known linked to obesity, experts have noted that the disease also seems to also be occurring in fit and healthy patients.
Some experts believe the explanation must lie in environmental factors young people have been exposed to more than previous generations.
While no ‘smoking gun’ has been found, there are multiple theories.
These include modern chemicals in diets, microplastics, pollution, and one recent study even pinned the surge on exposure to E. coli in food.
There are around 2,600 new bowel cancer cases in people aged 25-49 in Britain every year, and around 44,100 new cases among all ages.
Around 44,000 cases of bowel cancer are diagnosed every year in the UK, with about 130,000 in the US.
The disease kills almost 17,000 Britons each year, with the death toll rising to about 50,000 in America.
Overall, just over half of bowel cancer patients are expected to be alive 10 years after their diagnosis.
The health burden of obesity—which costs the UK economy billions—is one of the reasons why ministers are so keen to rollout revolutionary new weight loss jabs.
Sold under the brands Mounjaro Wegovy, increasing access to these drugs is one of one the cornerstones of the 10-year-plan for the NHS.
The analysis on US obesity-linked cancer deaths was presented at the ENDO 2025, the Endocrine Society’s annual meeting in San Francisco and has not been fully published.