In 1995, a report in the Annals of Surgery was published with the title “Who would have thought it? An operation proves to be the most effective therapy for adult-onset diabetes mellitus”. The study claimed that more than 80% of patients with type 2 diabetes (T2DM) and 99% of patients with prediabetes were completely cured after surgery. Since then, a number of observational studies and randomized clinical trials set out to assess the fate of T2DM after bariatric surgery. Early hypotheses regarding T2DM resolution after roux en-y gastric bypass (RYGB) related remission to weight loss after surgery. However, subsequent research showed that the improvement in glucose levels is rapid and precedes significant weight loss.
A number of theories that aimed to explain the early and rapid improvement of blood glucose levels after bariatric surgery emerged. The hindgut theory states that T2DM control results from rapid delivery of nutrients to the small intestine, enhancing the release of hormones such as glucagon-like peptide-1 (GLP-1). The foregut theory states that exclusion of the proximal small intestine causes a reduction in the secretion of anti-incretin hormones, leading to improvement of blood glucose control. In fact, the elevation in GLP-1 levels after RYGB causes an increase in insulin secretion and a reduction in glucagon secretion, thereby improving glucose metabolism. Studies have also shown that improved intestinal gluconeogenesis may be involved in the improvement of glucose levels after RYGB. However, neither theory completely explains the mechanism of how T2DM rapidly resolves after RYGB. It is now thought that RYGB resolves T2DM through: (1) Alteration of bile flow, (2) Reduction of gastric size, (3) Rearrangement of gut anatomy and altered flow of nutrients, (4) Manipulation of the vagus nerve, and (5) Modulation of gastrointestinal hormones.
Regardless of the mechanism, resolution of T2DM is well-proven after RYGB. Philip Schauer and colleagues demonstrated in a large clinical trial that bariatric surgery is superior to intensive medical therapy in ameliorating T2DM, and that effects are sustained for the 3-year duration of the trial. In the latest long-term meta-analysis to date, it was found that two-thirds of patients with T2DM have complete and sustained remission after RYGB. Additionally, the Swedish Obese Subjects (SOS) study found that patients with T2DM who underwent T2DM were less likely to develop microand macrovascular complications of T2DM. Moreover, those who had bariatric surgery had better long-term survival rates.
Bariatric surgery remains the most effective treatment for severe obesity and co-morbidities. With the grave longterm consequences of T2DM, it becomes important to offer RYGB to obese patients with this disease.