Bariatric surgery reduces the risk of cancer in populations with obesity. It is unclear if weight loss alone or physiologic changes related to bariatric surgery cause this protective effect. We evaluated the relationship between surgical weight loss and changes in serums biomarkers with incident cancer in a bariatric surgery cohort.


The Longitudinal Assessment of Bariatric Surgery 2 is a prospective multi-center cohort (N = 2353, 79% female, mean age at baseline = 46). We evaluated weight and serum biomarkers, measured preoperatively and one year after surgery, as predictors for incident cancer. Associations were determined using Cox proportional hazards models adjusting for age, sex, education, and smoking history.


Over 8759 person-years of follow-up, 82 patients reported new cancer diagnosis (936 per 100,000 person-years, 95%CI: 749–1156), 55 were cancers thought to be associated with obesity. Achieving a BMI < 30 kg/m2 was associated with a lower risk of cancer (HR=0.59, 95%CI: 0.34–1.00), as was losing at least 20-34.9% total body weight (vs <20%, HR=0.44, 95%CI: 0.25–0.76). Baseline BMI ≥ 50 kg/m2 (vs BMI <40kg/m2) was associated with more incident cancer (HR=1.40, 95%CI: 0.68-2.86). Decreased post-operative glucose, proinsulin, insulin, and leptin levels were association with decreased cancer risk (Table 1)


Achieving cancer-risk reductions through bariatric surgery may require losing >20% total body weight or lowering BMI below the obesity threshold. Surgery may not decrease cancer risk in patients with baseline BMI ≥ 50 kg/m2. Metabolic changes after bariatric surgery likely play a role in the decreased risk of cancer.