Weight Loss Surgery Reduces Cancer Risk, Study Finds

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New preliminary research this week points to long term benefits from bariatric, or weight loss, surgery. The study found that people who underwent surgery were noticeably less likely to develop certain cancers over a ten-year period compared to similarly matched people with obesity who did not receive surgery. Those who did develop cancer were also less likely to die from it.

The study was led by researchers at the Gundersen Lutheran Health System in Wisconsin. They examined the medical records of over 1,000 patients who received surgery at their hospital, dating back to 2001. These patients were compared to a control group of nearly 2,000 nonsurgical patients who were matched on factors like sex, age, and baseline body mass index ( BMI). Their cancer-related outcomes were then tracked over a 10-year period.

During those years, the odds of a new cancer diagnosis were significantly smaller in the surgery group compared to the control (5.2% vs. 12.2%). The largest reductions in risk were seen for breast cancer (1.4% vs 2.7%), reproductive tract cancers in women, (0.4% vs 2.6%), and kidney cancer (0.10% vs. 0.80%). Additionally, the 10-year survival rate for cancer patients was 92.9% in the bariatric group vs. 80.6% for control patients.

The findings were presented this week at the American Society for Metabolic and Bariatric Surgery (ASMBS) Annual Meeting and have yet to be published in a peer-reviewed journal, an important part of the scientific process. But this is the latest research to show that bariatric patients experience better health outcomes, including reduced cancer risk, following surgery. In fact, a separate paper presented this week at the ASMBS found that surgery patients were 37% less likely to develop colorectal cancer.

“This study also sheds light on the various cancers that obesity can cause, as well as to what extent bariatric surgery can reduce cancer risk,” co-author Jared Miller, a general and bariatric surgeon at Gundersen Lutheran, told Gizmodo in an email. “We believe this information is vital in informing other health care professionals of how a cancer specific to each specialty can be affected by bariatric surgery.”

There are various forms of bariatric surgery, but the majority of them usually involve permanently resculpting the digestive tract. Patients then tend to lose substantial amounts of weight and keep it off—something that’s very hard to accomplish through typical dietary and lifestyle changes. Most of the cancer-related benefits from surgery come from that weight loss, Miller says, though there may be other bodily changes involved as well. He points out that obesity has been linked to increased inflammation, changes in the gut microbiome, and altered hormone levels—all mechanisms that could contribute to cancer risk and survival.

While the study’s findings show the continued value of bariatric surgery, at least for those able and willing to access it, they may hold implications for the treatment of obesity in general. In recent years, there have been drugs developed that appear to be far more effective than past treatments at helping people lose weight. In May, Eli Lilly’s Mounjaro was approved for type 2 diabetes, and it’s expected to be approved for obesity later this year or next. Large-scale trials have found that people taking Mounjaro have lost up to 20% or more of their weight—numbers just below the average weight loss seen with typical bariatric surgery.

For now, though, the long-term health benefits of these newer pharmaceutical treatments is still an open question. And while interventions like dieting, exercise, and drugs can help people lose weight, Miller notes that only bariatric surgery has shown these kinds of sustained improvements in health so far.

ASMBS president Shanu Kothari, who is not affiliated with the research, agrees that it will take time to know whether these drugs can match the potential of surgery in helping treat or prevent obesity-related conditions like cancer.

“Future studies will have to be done to see if weight loss with pharmaceutical intervention will provide the same cancer risk reduction as bariatric surgery,” he told Gizmodo in an email.

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