Obesity and type 2 diabetes cause perturbations in metabolism and immunity that increase the risk of cancer. Bariatric surgery is the most effective intervention for substantial and enduring weight loss in those with obesity and has been shown to [reverse type 2 diabetes](​​https://pubmed.ncbi.nlm.nih.gov/33485454/) and reduce cancer risk. Findings of a recent report demonstrate a lower risk of cancer in patients with obesity and diabetes up to 31 years following bariatric surgery.

Weight gain occurs when the body stores excess calories in the form of fat in adipose tissue depots around the body. As the amount of energy stored increases, the body’s tolerance for glucose and other fuels decreases, leading to insulin resistance and type 2 diabetes. The high circulating levels of glucose, insulin, insulin-like growth factors, and inflammatory proteins observed in type 2 diabetes increase cancer cell proliferation and suppress apoptosis (programmed cell death). Reducing energy stores through bariatric surgery or other weight-loss therapies restores insulin sensitivity and reduces cancer risk.

The authors collected data from an ongoing trial with over 4,000 participants investigating the long-term effects of bariatric surgery in adults with obesity and type 2 diabetes. At their baseline visit, participants underwent a physical exam, gave a blood sample, and completed questionnaires regarding health and lifestyle factors. Participants chose to undergo bariatric surgery or receive conventional obesity treatment during the years of 1987 and 2001. They continue to provide additional questionnaire data and blood samples as the study remains ongoing. The investigators followed participants in the current sample for an average of 21 years.

Participants who chose to undergo bariatric surgery lost an average of 60 pounds two years after the baseline visit, compared to just 7 pounds in participants who received standard obesity treatment. These levels of weight loss remained stable 10 years after the baseline visit. At two years follow-up, 70 percent of participants who underwent surgery had diabetes remission, compared to 34 percent at 10 years follow-up. Bariatric surgery reduced cancer risk by 48 percent in women and 37 percent in the whole group. Participants who underwent surgery and maintained diabetes remission after 10 years had 55 percent reduction in cancer risk compared to participants with diabetes at 10 years follow-up. Participants who did not undergo surgery but achieved diabetes remission had an even greater risk reduction of 60 percent at 10 years follow-up.

These findings support long-term weight-loss, including bariatric surgery, as a strategy to reduce type 2 diabetes and cancer risk among adults with obesity.

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• Learn more about the effects of obesity and type 2 diabetes on breast cancer risk in this clip with expert Dr. Ruth Patterson.