A higher body mass index (BMI) increases the risk of 10 of the most common forms of cancer, according to a British study of more than 5 million adults. Risk can amount to an increase of more than 60 percent, depending on the type of cancer.
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BMI is a measure of body fat based on height and weight. A BMI of 25 is considered overweight, and a BMI of at least 30 is classified as obese. (To calculate your BMI, go here.)
Researchers at the London School of Hygiene &Tropical Medicine found that for every five point increase in BMI — the equivalent to approximately 39 pounds — risk was increased 62 percent for cancer of the uterus, 31 percent for gallbladder cancer, 25 percent for kidney cancer, 10 percent for cancer of the cervix, and 9 percent for both thyroid cancer and leukemia.
Higher BMI also increased the risk of liver cancer (19 percent), colon (10 percent,) ovaries (9 percent), and breast (5 percent), although other factors influenced risk in these categories.
Increasing numbers of people who are overweight or obese will mean thousands of additional deaths every year, says lead author Dr. Krishnan Bhaskaran of the London School of Hygiene & Tropical Medicine. "The number of people who are overweight or obese is rapidly increasing both in the U.K. and worldwide," said Bhaskaran. "It is well recognized that this is likely to cause more diabetes and cardiovascular disease. Our results show that if these trends continue, we can also expect to see substantially more cancers as a result."
Even within normal BMI ranges, higher BMI was associated with increased risk of some cancers. Conversely, there was some evidence that those with high BMI were at a slightly reduced risk of prostate cancer and premenopausal breast cancer.
"There was a lot of variation in the effects of BMI on different cancers," said Dr. Bhaskaran. "For example, risk of cancer of the uterus increased substantially at higher body mass index; for other cancers, we saw more modest increases in risk, or no effect at all. For some cancers like breast cancer occurring in younger women before the menopause, there even seemed to be a lower risk at higher BMI. This variation tells us that BMI must affect cancer risk through a number of different processes, depending on the cancer type."
Based on the results, the researchers estimate that excess weight could account for 41 percent of all uterine cancer in the U.K., as well as 10 percent or more of gallbladder, kidney, liver, and colon cancers.
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