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Cancer Risk Drops in Half With Over 20% Weight Loss After Bariatric Surgery



New Study by the Oregon Health & Science University School of Medicine and presented to the American Society for Metabolic and Bariatric Surgery ASMBS on the 5th November 2019  – Compares differences in Cancer Risk Reduction among Weight-Loss Surgery Patients.

Patients with severe obesity who had bariatric or weight-loss surgery and lost more than 20% of their total weight were 50% less likely to develop cancer compared to patient who did not.  Researches by the Oregon health & Science University to the ASMBS Annual Meeting at Obesity Week 2019.

Data from 2,107 adults who underwent bariatric surgery, either lap gastric bypass or banding.  The average age of the patients were 46 79% female, and a third had type 2 diabetes and 44% had a history of smoking before surgery.   Weight and cancer serum biomarkers (proteins detected in the blood, urine or . body tissue ) were measured preoperatively and one year after surgery as predictors for incident cancer after adjusting for age, sex, education and smoking history.

Researches found having a BMI of 30 or more one year after bariatric surgery was suggestive of a 60% higher risk of cancer compared to having a BMI under 30.  6.2% of those that lost less than 20% of their body weight reported a cancer diagnosis by year 7, compared to about 3.6% who lost 20% or more of their total body weight – representing a 50% reduction.  Overall the average BMI at 12 months after surgery was 33 and the average excess weight loss was 58%.

The most common cancer type was breast cancer (34%), followed by thyroid (8.5%), melanoma (7%), colon (6%), kidney (6%), uterine (5%), and lung (4%), (3%) other cancers.

Their data suggests that there is a weight loss threshold, that if achieved, significantly reduces risk of cancer in post-bariatric surgery patients.  There seems to b e a variability in the protective effect of bariatric surgery that is dependent on the degree of weight loss.

The Researches also found that metabolic changes after bariatric surgery contributed to lowering the risk of cancer.  For each 20% reduction in leptin, a hormone released from the fat cells located in adipose tissue, there was a 20% reduction in cancer incidence.  Decreases in diabetes-related fasting glucose, proinsulin, insulin and C-peptide levels and increased levels of ghrelin, the hunger hormone, were also associated with reduced cancer risk.

According to the American Society of Clinical Oncology (ASCO), obesity is a major unrecognised risk factor for cancer.  There is increasing evidence linking it to several cancers including those of the breast, prostate and colon.  Obesity has also been associated with an increased risk of recurrence and mortality in patients with cancer.

Obesity is linked to more than 40 diseases including type 2 diabetes, hypertension, heart disease, stroke, sleep apnea, osteoarthritis and at least 13 different types of cancer.

In 2017, 228,000 bariatric and metabolic procedures were performed in the US which is less than 1% of the population with severe obesity.  39% of adults in the US had obesity in 2015-2016.

Metabolic/bariatric surgery has been shown to be the most effective and long-lasting treatment for severe obesity, resulting in significant weight loss and resolution or improvement in diabetes heart disease, sleep apnea and other related diseases.

The safety profile of laparoscopic bariatric surgery is comparable to some of the safest and most commonly performed surgeries, including gallbladder, appendectomy, and knee replacement.

For more information visit: www.asmbs.org


Study by Lead Author Andrea Stroud, MD, MS, Professor of Surgery, Division of Bariatric Surgery, Oregon University, Portland.

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