Digestive Diseases

June 26, 2024

Roux-en-Y gastric bypass (RYGB) has been associated with high rates of type 2 diabetes mellitus (T2DM) remission. The procedure involves creating a small gastric pouch and bypassing the proximal portion of the small intestines. In addition to promoting weight loss, RYGB provides substantial advantages in metabolic regulation.

RYGB appears to stimulate intestinal mechanisms conducive to T2DM remission that are independent of weight loss. This benefit has not been observed in patients who undergo procedures such as sleeve gastrectomy (SG) that do not bypass the proximal small intestines. These metabolic improvements are often underestimated and obscured by the dramatic weight loss observed in the short term and midterm after RYGB.

Mayo Clinic researchers recently sought to gain a better understanding of continued diabetes remission in patients who experience weight recurrence after RYGB. To examine this phenomenon more closely, they conducted a retrospective review of patients who underwent RYGB and SG and compared rates of continued diabetes remission among these two patient cohorts. The results of this study were published in the Journal of the American College of Surgeons in 2024.

"This study is particularly relevant right now due to the increasing prevalence of obesity and type 2 diabetes mellitus worldwide," explains Barham K. Abu Dayyeh M.D., M.P.H., the corresponding author on the study publication. "With obesity being a major risk factor for type 2 diabetes mellitus, and both conditions significantly impacting mortality and morbidity, identifying effective interventions is crucial." Dr. Abu Dayyeh is a gastroenterologist who leads the Advanced Endoscopy Innovation Translation and Clinical Trials Group at Mayo Clinic in Rochester, Minnesota.

Study methods

Study participants included patients with a body mass index of 35 kg/m² or more and a preoperative diagnosis of T2DM who underwent successful primary RYGB or SG between 2008 and 2017. The researchers identified a total of 224 patients in the RYGB group and 46 patients in the SG group with at least five years of follow-up who had weight recurrence and T2DM remission at their lowest weight. Baseline characteristics and demographics of both groups were comparable.

Results

"Overall, the study results suggest that gastric bypass, specifically RYGB, is a promising means to achieve both weight loss and the remission of type 2 diabetes mellitus, independent of weight loss," explains Dr. Abu Dayyeh. "We observed that RYGB can sustain type 2 diabetes mellitus remission even when patients experience significant weight recurrence, which is a breakthrough insight."

• At the final follow-up, the rate of continued diabetes remission was significantly higher in the RYGB group (75%, n = 168) than in the SG group (34.8%, n = 16).
• The odds of T2DM recurrence in the SG group were 5.5 times higher than in the RYGB group.
• After determining the optimal procedure for glycemic control, the researchers stratified the rates of continued diabetes remission into weight recurrence quartiles and compared outcomes.
  • 85.5% of participants had mild weight recurrence of less than 25%.
  • 81.7% of participants had moderate weight recurrence of 25% to 44.9%.
  • 63.2% of participants had severe weight recurrence of 45% to 74.9%.
  • 60% of participants had complete weight recurrence of more than 75%.
• Baseline insulin use, higher hemoglobin A1C levels and longer preoperative duration of T2DM were associated with T2DM recurrence, while weight recurrence was not.

Conclusions

The discrepancy in continued diabetes remission rates in the RYGB and SG groups suggests that the proximal small intestines play an important role in T2DM remission.

"These findings challenge the conventional belief that type 2 diabetes mellitus remission is primarily due to weight loss, highlighting the role of surgical and endoscopic interventions that alter intestinal physiology in managing metabolic diseases," says Dr. Abu Dayyeh.

"The metabolic benefits of RYGB may extend beyond mere weight reduction and involve physiological changes that can modify metabolic disease, such as alteration of the gut's hormonal environment, microbiome, enteric nervous system signaling, inflammation, bile acid signaling and nutrient absorption pathways. Clinically, these findings can guide more informed decisions regarding surgical options for obesity and diabetes management and usher in a new era of anatomy preserving interventions targeting the intestines for management and modification of type 2 diabetes mellitus.

Next steps

Dr. Abu Dayyeh notes that the idea that RYGB facilitates a weight loss-independent mechanism, potentially through alterations in gut hormones or microbiota, needs further exploration. "Future research should focus on identifying specific changes in the gut environment after RYGB that contribute to sustained metabolic improvements," says Dr. Abu Dayyeh. "Prospective, longitudinal studies could also investigate the long-term outcomes of different bariatric and endoscopic interventions to confirm and extend these findings."

Mayo Clinic researchers are involved in additional, broader efforts to understand and optimize treatment for metabolic diseases. These efforts include studies exploring similar surgical and nonsurgical interventions that might replicate the benefits observed with RYGB. "Collaborations among researchers engaged in this work are crucial if we are to develop treatments utilizing the gut as a therapeutic target to provide sustained remission and improvement of type 2 diabetes mellitus," says Dr. Abu Dayyeh.

For more information

Ghanem OM, et al. Continued diabetes remission despite weight recurrence: Gastric bypass long-term metabolic benefit. Journal of the American College of Surgeons. 2024;238:862.

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