Weight-loss surgery can deliver a host of health benefits, but new research reveals an unexpected one: Getting the surgery was associated with a 40% lower risk of blood cancers.

Being overweight or obese is a risk factor for several types of cancer, and women with obesity have a higher risk of cancer than men do.

In the study, researchers used data from the Swedish Obese Subjects (SOS) study at the University of Gothenburg and the Cancer Registry at the National Board of Health and Welfare to study more than 2,000 people who had bariatric (weight-loss) surgery and then compare them to more than 2,000 other people who were also obese but didn’t have the surgery.

During the follow-up period, 34 of the patients in the surgery group developed blood cancer and also had significant weight loss. In the control group, 51 people developed blood cancer but remained obese.

Most of the blood cancers seen in the study were lymphomas. When these were studied separately, there was a 55% reduction in the risk of lymphoma in the group that had undergone bariatric surgery.

Women with high blood sugar (“glucose”) at the start of the study seemed to benefit the most from bariatric surgery, the investigators found.

The findings were published online recently in The Lancet Healthy Longevity.

“The benefit of the surgery is linked to baseline blood glucose levels. The reduced risk of [blood] cancer was much more pronounced if the women’s blood sugar levels were high at the beginning, which clearly shows that blood sugar is an important factor in cancer development,” said corresponding author Magdalena Taube. She is an associate professor of molecular and clinical medicine at Sahlgrenska Academy at the University of Gothenburg.

What happens to create the link between obesity and blood cancers is complex, the authors said. It may involve chronic inflammation and a type of genetically related risk factor for blood cancer.

Metabolic improvements that take place after bariatric surgery, including reduced inflammation, may reduce the risk of cancer, the researchers suggested.

“The results provide further support of considering obesity a risk factor for [blood] cancer, and that bariatric surgery can reduce the risk of blood cancer in obese women,” Taube said in a university news release.

More information

The American Society of Hematology has more on blood cancers.

SOURCE: University of Gothenburg, news release, Sept. 20, 2023