Scientists have long thought that obesity is linked to cancer, but now, the evidence is even stronger. An umbrella review of meta-analyses and systemic reviews have founds that obesity increases the risk of 11 cancers, namely:
- Esophageal cancer (adenocarcinoma)
- Multiple Myeloma
- Cancer of the stomach (gastric cardia)
- Colon cancer (in men)
- Cancer of the rectum
- Biliary tract cancers (cancers of gallbladder, extrahepatic bile duct, and ampulla of Vater)
- Pancreatic cancer
- Breast cancer (in post-menopausal women)
- Womb cancer (endometrial cancer, in pre-menopausal women)
- Ovarian cancer
- Cancers of the kidney
The Study: Obesity Increases Cancer Risk
The study subject 95 meta-analyses which tied obesity to cancer under scrutiny, and came to the conclusions about the 11 cancers above. Obesity was defined as a Body Mass Index (BMI) of more than 30 kg/m2.
Other cancers which may be increased with obesity include cancers of the skin (melanoma), thyroid, lung and leukemia.
The degree of risk varies amongst different cancers and sexes, with a graded increase in risk with weight. For example, there is a 30% higher risk of colon cancer for each 5 kg/m2 increase in body mass index in men. The risk was less in women, with a 12% increase in risk for each 5 kg/m2 increase in body mass index.
Amongst men, the increase in the risk of developing cancer for every 5 kg/m2 increase in body mass index ranged from 9% (relative risk 1.09, 95% confidence interval 1.06 to 1.13) for rectal cancer to 56% (1.56, 1.34 to 1.81) for biliary tract system cancer.
What does this study mean for us?
It is still not perfect, as it is a an analysis of previous studies – and to confirm the causal association, randomised, controlled prospective studies are still required. However, it is nonetheless important in proving that obesity not only increases our risks of heart disease and metabolic syndrome, but also cancers as well.
Hence, it is important to eat healthy, exercise, and maintain a healthy weight, if we want to minimise disease later in life.