A large international study has strengthened the evidence that excess body weight can raise the risk of several types of cancer. Researchers reviewed decades of data from around the world and found that a higher Body Mass Index (BMI) is linked to an increased risk of 19 different cancers. The findings were published in Nature Metabolism and are among the most comprehensive analyses on the link between obesity and cancer to date.
BMI is a measure that estimates whether a person's weight is appropriate for their height. While it does not directly measure body fat, it is widely used as a simple screening tool. The new review analysed information from 226 studies involving about 1.5 million cancer cases. Researchers found that as BMI increases, the risk of several cancers also rises.
What Did The Study Find?
The researchers found a positive association between higher BMI and 19 cancer types. Some of the strongest links were seen for endometrial cancer, which affects the lining of the uterus, and oesophageal adenocarcinoma, a type of cancer that develops in the food pipe. According to the analysis, every five-unit increase in BMI was associated with a 58% higher risk of endometrial cancer and a 47% higher risk of oesophageal adenocarcinoma.
The review also found links between higher BMI and several cancers that have received less attention in the past. These included leukaemia, non-Hodgkin lymphoma, bladder cancer and glioma, a type of brain tumour. Researchers say these findings expand current understanding of how excess body weight may influence cancer development.
Why Does Excess Weight Increase Cancer Risk?
Researchers believe there may be several biological processes that can explain the link. Excess body fat can lead to chronic inflammation, which may damage cells over time. Obesity is also linked to higher levels of certain hormones, including insulin and oestrogen, which can lead to abnormal cell growth. In addition, excess fat tissue can impact the body's metabolism and create an environment that may lead to cancer development.
Also, obesity may affect the size and function of certain organs, increasing the number of cells that could potentially become cancerous. Although the exact mechanisms are still being studied, experts agree that the relationship between obesity and cancer is complex and involves multiple pathways.
Not All Cancer Risks Were Higher
Interestingly, the study found that higher BMI was linked to a lower risk of a few specific cancers, including premenopausal breast cancer. However, researchers say that these findings do not mean excess weight is protective overall. The overall findings still show that obesity is a major health concern and is associated with increased risk for many serious diseases, including numerous cancers.
The researchers also compared BMI with waist circumference, another measure often used to assess body fat. They found that both measurements had similar results when predicting cancer risk, although there were some differences for certain cancer types.
What Does This Mean For Public Health?
Obesity rates have been rising worldwide, making these findings particularly important. Health organisations for long have recognised obesity as a risk factor for several cancers, but this new analysis suggests the impact may be even higher than previously understood. Experts say maintaining a healthy weight through balanced eating, regular physical activity and other lifestyle measures could help reduce future cancer risk.
The authors also found that some regions, including parts of South Asia and Africa, remain underrepresented in long-term cancer studies. More research involving diverse populations will be needed to better understand how obesity affects cancer risk across different groups.
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