For many years, we have known that obesity increases one’s risk for developing cancer in various parts of the body. According to the Centers for Disease Control and Prevention, obesity is a leading cause of preventable cancers, along with smoking, heavy drinking and exposure to ultraviolet radiation. People who are overweight or obese have a higher risk of developing 13 different types of cancer, including endometrial (uterine), breast, kidney, liver, esophageal and colon. The C.D.C. estimates that the 13 types of cancer linked to obesity make up 40 percent of all cancers diagnosed in the United States each year.

But that doesn’t necessarily mean that this risk can be reduced by weight reduction, or does it? Now we are starting to answer this question: A large new study found that people who lost significant amounts of weight through bariatric surgery (designed to reduce the stomach’s capacity or to bypass it entirely) gained a striking benefit: Their likelihood of developing cancer fell sharply. The study, published in the AMA journal, followed more than 30,000 adults with obesity for about a decade. It found that those who underwent bariatric surgery had a 32 percent lower risk of developing cancer and a 48 percent lower risk of dying from the disease, compared with a similar group of people who did not have the surgery and failed to lose weight. On average, the people who had weight loss surgery lost about 55 pounds more than those who did not over the course of the study. The researchers found that the more weight people lost, the more their cancer risk fell. This latter finding provides important confirmation that weight reduction actually diminishes chances of cancer development.

While the new research focused on weight loss through bariatric surgery, the authors of the study believed that the benefit would apply to weight loss through other methods as well, such as diet and exercise. A co-author of the study, said “the findings provide one more reason why people who are obese should lose weight,” stating further that “ I think a lot of the public doesn’t understand or realize that obesity is such a strong risk factor for cancer, and they certainly don’t understand that it’s reversible.”

One expert, who was not involved in the study, said that it demonstrates that treating obesity and achieving “clinically meaningful weight reductions can improve health outcomes for patients,“ that add cancer protection to the already many known health benefits of such weight reduction.

It is not entirely clear why obesity seems to promote cancer, but one potential factor is inflammation. Studies show that fat cells spew into the bloodstream a variety of inflammatory proteins known as cytokines, which have been found to stimulate cancer cells. Many scientists believe this chronic state of inflammation caused by fat cells is also one of the reasons people with obesity have higher rates of complications from Covid-19. Fat cells are often thought of as being inert—that they’re just sitting there and not doing anything. But, in fact, they’re metabolically active. It is likely that the chronic inflammation produced by obesity, by these very metabolically active fat cells, is one of the mechanisms by which cancer is induced. According to the C.D.C., people with obesity also tend to have higher levels of hormones such as insulin and insulin-like growth factors which could stimulate the development of colon, kidney, prostate and endometrial cancers.


No matter how the benefits are achieved, this information provides a powerful incentive for all those who are overweight to reduce their weight as much as possible. My preference is to accomplish this through diet and exercise, but if that’s not possible, bariatric surgery may be a last resort.



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