Now a study in the New England Journal of Medicine gives us a better idea of how effectively it works.
More than 3,400 adults were followed for over 15 years. Some patients had bariatric surgery and others did not.
The study found that, although weight loss alone helped prevent diabetes in obese people, bariatric surgery reduced the long-term incidence of the disease by 78 percent.
The conclusion: Bariatric surgery is twice as efficient as lifestyle changes in the prevention of type-2 diabetes.
