Roux-en-Y Gastric Bypass Increases Glycemic Variability and Time in Hypoglycemia in Patients With Obesity and Prediabetes or Type 2 Diabetes: A Prospective Cohort Study

Diabetes Care. 2021 Feb;44(2):614-617. doi: 10.2337/dc20-1609. Epub 2020 Dec 17.


Objective: Roux-en-Y gastric bypass (RYGB) is an established treatment for type 2 diabetes and obesity. The study objective was to establish RYGB's effects on glycemic variability (GV) and hypoglycemia.

Research design and methods: This was a prospective observational study of 10 participants with obesity and prediabetes or type 2 diabetes who underwent RYGB. Patients were studied before RYGB (Pre) and 1 month, 1 year, and 2 years postsurgery with continuous glucose measurement (CGM). A mixed-meal test (MMT) was conducted at Pre, 1 month, and 1 year.

Results: After RYGB, mean CGM decreased (at 1 month, 1 year, and 2 years), and GV increased (at 1 year and 2 years). Five of the 10 participants had a percent time in range (%TIR) <3.0 mmol/L (54 mg/dL) greater than the international consensus target of 1% at 1 or 2 years. Peak glucagon-like peptide-1 (GLP-1) and glucagon area under the curve during MMT were positively and negatively associated, respectively, with contemporaneous %TIR <3.0 mmol/L.

Conclusions: Patients undergoing RYGB are at risk for development of postbariatric hypoglycemia due to a combination of reduced mean glucose, increased GV, and increased GLP-1 response.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Glucose
  • Diabetes Mellitus, Type 2* / complications
  • Gastric Bypass* / adverse effects
  • Humans
  • Hypoglycemia* / etiology
  • Insulin
  • Obesity / complications
  • Obesity, Morbid* / surgery
  • Prediabetic State*
  • Prospective Studies


  • Blood Glucose
  • Insulin

Associated data

  • figshare/10.2337/figshare.13260275