Bariatric Surgery and Prevention of Type 2 Diabetes in Swedish Obese Subjects

Study Questions:

What are the long-term effects of bariatric surgery, compared to usual care, on the prevention of type 2 diabetes in participants of the SOS (Swedish Obese Subjects) study?


This was a nonrandomized, prospective, controlled intervention trial of 1,658 patients who underwent bariatric surgery, and 1,771 obese matched controls who received usual care (ranging from no treatment to advanced lifestyle modification). Participants were followed for up to 15 years, and the rate of incident type 2 diabetes (as determined by self-reporting of hypoglycemic medications or fasting glucose levels) was the outcome of interest.


The median follow-up time was 10 years, and the rate of loss to follow-up was 36.2% at 15 years. Type 2 diabetes developed in 392 patients in the control group (incidence of 28.4 cases per 1,000 person-years) and 110 patients in the bariatric surgery group (6.8 cases per 1,000 person-years). The adjusted hazard ratio with surgery was 0.17 (95% confidence interval, 0.13-0.21; p < 0.001). At 15 years, the average weight loss in the bariatric surgery group was approximately 20 kg; mean weight changes in the control group never exceeded 3 kg. With respect to the incidence of diabetes, the interaction between treatment and body mass index (BMI) was not significant. Obese patients with impaired fasting glucose had the greatest benefit from bariatric surgery (p = 0.002 for the interaction).


In this obese Swedish population, bariatric surgery reduced the long-term incidence of type 2 diabetes by 78%. While BMI did not influence the beneficial impact of bariatric surgery, the preventive effect of surgery was particularly prominent among participants with impaired fasting glucose.


Although not randomized, the SOS study suggests that bariatric surgery may be far more efficient in preventing incident type 2 diabetes than is conventional lifestyle modification. The inability of BMI to predict a benefit of bariatric surgery has implications for the selection of patients who would most benefit from this intervention. If confirmed with a randomized trial design, the SOS findings may support the argument for bariatric surgery as a means to prevent diabetes in appropriately selected patients.

Clinical Topics: Prevention, Diet

Keywords: Prediabetic State, Bariatric Surgery, Life Style, Weight Loss, Body Weight, Glucose, Incidence, Body Mass Index, Cardiovascular Diseases, Obesity, Hypoglycemic Agents, Diabetes Mellitus, Fasting

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