New research suggests excess weight may account for more than one in 10 cancers—nearly double previous estimates.
The study, published in Cancer Communications, was led by researchers at the German Cancer Research Center (DKFZ), who analyzed health data from 458,543 participants in the UK Biobank and tracked them for a median of nearly 12 years.
During that time, more than 50,000 new cancer cases were recorded.
Obesity has long been recognized as a risk factor for multiple cancers, but earlier studies generally estimated that excess weight accounts for between 2 percent and 8 percent of cancer cases.
The new analysis suggests the true figure could be much higher.
After accounting for methodological limitations in previous research, the team estimated that as many as 11.5 percent of all cancer cases may be linked to excess body weight.
One reason for the discrepancy is the way obesity has traditionally been measured. Many studies rely on body mass index (BMI), which uses weight and height to estimate body fat.
However, BMI cannot distinguish between fat and muscle mass and provides little information about where fat is stored in the body.
The researchers found that measures such as waist circumference and waist-to-hip ratio—which better capture abdominal fat—were more informative when assessing cancer risk.
Abdominal fat is known to be metabolically active and has been linked to inflammation and other biological processes that may promote tumor development.
The team also identified another factor that may have skewed earlier estimates: weight loss caused by undiagnosed cancer.
Many tumors can trigger unintentional weight loss years before a diagnosis is made. As a result, some people may appear relatively lean when they enter a study, even though an existing cancer is already affecting their weight.
This can weaken the observed relationship between obesity and cancer risk.
To address this issue, the researchers excluded the first years after participants enrolled in the study, reducing the chance that pre-existing cancers would distort the results.
When they did so, the association between excess weight and cancer became substantially stronger.
The findings also suggest the impact of obesity on cancer risk may be greater among women than men and may play a larger role in adults younger than 60.
Lead researcher Hermann Brenner said the results highlight the growing public health importance of tackling obesity.
With obesity rates continuing to rise worldwide and populations aging, Brenner warned that the number of cancers linked to excess weight is likely to increase significantly in the coming years.
Effective prevention and treatment strategies for obesity, he said, could therefore have a much larger impact on cancer prevention than previously believed.
Reference
Luna Kiran Adhikari, Fatemeh Safizadeh, Marko Mandic, Hermann Brenner. Excess Weight May Account for More Than 10% of All Cancers: The Underestimated Impact of the Obesity Epidemic. Cancer Commun. 2026;46:0040.DOI:10.34133/cancomm.0040
