In 2017, the Centers for Disease Control and Prevention reported that 13 types of cancer were linked to obesity. Now, two recent studies presented at the American Society for Metabolic and Bariatric Surgery (ASMBS) Annual Meeting have found that bariatric surgery—commonly called weight loss surgery—is linked with reduced cancer risk among those who are overweight or severely obese, according to two ASMBS news releases. (Click here for the first release, and click here for the second release.)
The first study looked at the effects of bariatric surgery on women at genetic risk for breast cancer. Researchers reviewed the data of more than 1,670,035 patients with a body mass index (BMI) of 35 or greater. (That’s about 236 pounds for a 5-foot-9 man, 204 pounds for a 5-foot-4 woman.) Cancer incidence was compared between more than 1.4 million patients who didn’t undergo bariatric surgery and nearly 250,000 who did.
Study findings showed that women who had a genetic predisposition for breast cancer were 2.5 times more likely to develop a malignancy than women with the same genetic risk who underwent bariatric. Women who remained at a BMI of 35 or higher had an 18% cancer incidence compared with a 7.4% incidence for closely matched patients who had weight loss surgery. Researchers also found that weight loss surgery cut the overall risk of developing any obesity-linked cancers by 20%.
“Our findings suggest bariatric surgery could significantly prevent the development of cancer in patients with a higher risk than the average population, even in those genetically predisposed,” said study coauthor Emanuele Lo Menzo, MD, PhD, FASMBS, an associate program director at Cleveland Clinic Florida in Weston. “The effect we saw on patients genetically predisposed to developing breast cancer was remarkable, and we believe this is the first time a study has shown such an impact.”
In the second study, researchers compared cancer risk reduction among weight loss surgery patients, but differences in risk were based on the amount of weight loss after the procedure. They reviewed more than 2,000 adults who underwent bariatric surgery.
If a person had a BMI of 30 or more one year after surgery—that’s 203 pounds for a 5-foot-9 man, 174 pounds for a 5-foot-4 woman—he or she had a 60% higher risk of cancer compared with an individual with a BMI under 30. About 6.2% of people who lost less than 20% of their body weight reported a cancer diagnosis by year 7 compared with only 3.6% of patients who lost 20% or more of their total body weight.
Breast cancer was the most common cancer that developed among participants (34%), followed by cancers of the thyroid, colon, kidney, uterus and lungs as well as melanoma. While those ranged from 4% to 8.5%, incidence of bladder, cervical, prostate, brain, endometrial, esophagus, stomach and testicular cancers was less than 3%.
“Our data suggests that there is a weight loss threshold, that if achieved, significantly reduces risk of cancer in post–bariatric surgery patients,” said lead study author Andrea M. Stroud, MD, MS, an assistant professor at Oregon Health & Science University School of Medicine in Portland. “So there seems to be variability in the protective effect of bariatric surgery that is dependent on the degree of weight loss.”
For similar coverage, read “Women Who Lose Weight Can Lower Their Breast Cancer Risk” and “Being Overweight Raises Cancer Risk Twice as Much as Previously Thought.”