A major international review has found that higher body mass index (BMI) may increase the risk of 19 different types of cancer. The analysis expands the list of obesity-related cancers beyond the 13 currently recognized by leading health organizations.
The findings come from a systematic review and meta-analysis published in Nature Metabolism. Researchers analyzed data from more than 1.5 million cancer cases collected across 23 countries and found that excess body weight may play a broader role in cancer development than previously understood.
For years, organizations including the World Cancer Research Fund and the International Agency for Research on Cancer have warned that obesity raises the risk of several cancers. However, researchers said important questions remained about whether those risks differ across populations and whether newer genetic evidence supports the observed links.
To address those questions, the research team reviewed 226 peer-reviewed studies published through April 2025. The studies covered 25 common cancer types and included more than 1.5 million documented cancer cases from six major geographic regions.
Researchers standardized the data to measure cancer risk associated with every 5 kg/m² increase in BMI. They also used Mendelian randomization analyses, a genetic research method that helps determine whether observed associations may reflect causal relationships rather than simple correlations.
The analysis found statistically significant evidence linking higher BMI to an increased risk of 19 cancer types. The strongest associations were seen for endometrial cancer and esophageal adenocarcinoma.
According to the study, every 5-unit increase in BMI was associated with a 58% increase in endometrial cancer risk and a 47% increase in esophageal adenocarcinoma risk.
The review also identified positive associations between higher BMI and several cancers that have not previously been recognized as obesity-related in major consensus reports. Those included leukemia, non-Hodgkin lymphoma, bladder cancer, and glioma.
Researchers also observed inverse associations for premenopausal breast cancer, lung cancer among lifelong non-smokers, and esophageal squamous cell carcinoma among lifelong non-smokers.
The study found substantial differences in cancer risk across regions. For example, the association between BMI and postmenopausal breast cancer was significantly stronger in East Asian populations than in European populations.
Researchers said the finding suggests that results from Western populations may not always apply equally to other parts of the world.
The review also identified differences between men and women. The link between BMI and colorectal cancer was stronger in men, while the association between BMI and gallbladder cancer was stronger in women.
In addition, researchers compared BMI with waist circumference as a predictor of cancer risk. They found that both measurements produced broadly similar results, although some differences were observed for certain cancer types.
The authors said their findings reinforce evidence that obesity is a major contributor to the global cancer burden. They also noted that some regions, including Africa, South Asia, and Central America, remain underrepresented in long-term cancer studies.
The researchers called for more studies involving diverse populations to improve understanding of how excess body weight influences cancer risk around the world and to help guide future prevention strategies.