Many people try to lose weight to feel a bit better, move more easily, and maybe fit into that smaller pair of pants– but did you know that extra weight is also tied to about 20% of all cancers?
Because it’s difficult to control lifestyle factors at a major level, most studies linking weight to cancer are Observational in nature– meaning that we can look at what is happening in a population without actually controlling any variables. This data can be less reliable but, when many studies are viewed as a group, can indicate strong relationships. A study from The British Medical Journal evaluated over 200 observational studies and found a link between obesity, waist circumference, and weight gain and several cancers, with the strongest evidence linking obesity to esophageal, pancreatic, liver/gallbladder, colorectal, and kidney cancers — all related to the GI tract– as well as bone marrow and endometrial cancers.
The mechanism underlying the causation is unknown, though National Cancer Institute believes that a few key factors may contribute to the relationship:
- Inflammation: Obesity is generally accompanied by chronic inflammation, which is repeatedly linked to cellular dysfunction and cancer development.
- Hormones: Fat cells tend to excrete more estrogen than other cells, which may increase risks of hormone-sensitive cancers like breast or ovarian.
- Insulin: High body weight generally leads to higher insulin levels in the body, which may increase risk of colon, cancer, and endometrial cancers.
According to the American Cancer Society, the best advice for a cancer-free life is to stay lean without being underweight, meaning that a BMI between 18.5 and 25 (which is considered ‘normal’) is a good reference range. Even losing a small percentage of body weight can help lower health-related risks.
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