Weight loss is tied to lower cancer risk, new study shows

A large new study found that people who lost significant amounts of weight through bariatric surgery gained a striking benefit: Their likelihood of developing cancer fell sharply.

The study, published recently in JAMA, followed more than 30,000 adults with obesity for about a decade. It found that those who underwent weight loss 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.

While the new research focused on weight loss through bariatric surgery, the authors of the study speculated the benefit would apply to weight loss through other methods as well, such as diet and exercise or the use of weight loss medications. Dr. Steven E. Nissen, a coauthor of the study, said the findings “provide one more reason why people who are obese should lose weight.”

“It’s an important public health message,” said Nissen, the chief academic officer of the Heart, Vascular and Thoracic Institute at the Cleveland Clinic. “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.”

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, breast, kidney, liver, esophageal and colorectal. The CDC estimates the 13 types of cancer linked to obesity make up 40 percent of all cancers diagnosed in the United States each year.

Bariatric surgery can lead to substantial weight loss. Though some patients end up regaining some of the weight they lost, studies show that most people who undergo bariatric surgery are able to sustain a more than 20 percent reduction in their body weight a decade after their procedure.

For the new study, Nissen and his colleagues wanted to see how that amount of weight loss would affect cancer rates. They recruited 5,053 people with obesity who had undergone bariatric surgery at the Cleveland Clinic and followed them. Each patient was “matched” to five other patients who were similar in many respects — they were about the same age, sex and race, and they had similar medical histories and body mass indexes, but they did not undergo weight loss surgery.

All told, there were more than 30,000 participants in the study, which included 25,265 people in the control group.

After a decade, the patients who had the surgery had lost an average of about 61 pounds, while those in the control group (who were advised by their doctors to try to lose weight on their own) had lost an average of 6 pounds. Slightly less than 3 percent of patients who had surgery developed cancer, compared with roughly 4.9 percent of those in the nonsurgical group — equivalent to a 32 percent reduction in risk for those who had surgery.

In general, the data suggested that patients needed to lose a large amount of weight, at least 20-25 percent of their body weight, to see a beneficial change in their cancer risk, said Dr. Ali Aminian, the lead author of the study and the director of the Bariatric and Metabolic Institute at the Cleveland Clinic.