A major global study has found that excess body weight may be linked to a wider range of cancers than previously believed, with risks varying by cancer type, sex and region.
The research, published in Nature Metabolism, analysed data from more than 1.5 million cancer cases across 23 countries, making it one of the largest reviews of its kind. It found that higher body mass index (BMI) is associated with 19 different cancers, up from 13 previously recognised by global health bodies.
Researchers reviewed 226 studies and more than 500 BMI, cancer risk relationships, standardising results to show the effect of each 5-unit increase in BMI.
The study found the clearest links in endometrial and oesophageal adenocarcinoma cancers. Every five-unit rise in BMI increased risk by 58 percent for endometrial cancer and 47% for oesophageal adenocarcinoma.
New associations were also identified for leukaemia, non-Hodgkin lymphoma, bladder cancer, and glioma, cancers not previously included in some obesity-related risk lists.
While most associations showed increased risk, the study found some exceptions. Higher BMI was linked to a lower risk of premenopausal breast cancer and certain lung cancers in never-smokers.
The researchers also found strong variation depending on geography and sex. For example, the BMI–breast cancer link was nearly twice as strong in East Asian women compared to European women.
In men, BMI was more strongly linked to colorectal cancer, while in women, the association with gallbladder cancer was higher.
When comparing BMI with waist circumference, both measures showed similar links to cancer risk, though with some differences depending on cancer type.
The researchers say obesity remains a major cancer risk factor globally, but warn that many regions, especially Africa, South Asia, and Central America, remain under-represented in research.
They say future studies must include more diverse populations to better understand how body weight influences cancer risk worldwide
