Roux-en-Y gastric bypass compared with equivalent diet restriction: Mechanistic insights into diabetes remission

Diabetes Obes Metab. 2018 Jul;20(7):1710-1721. doi: 10.1111/dom.13287. Epub 2018 Apr 10.


Aims: To investigate the physiological mechanisms leading to rapid improvement in diabetes after Roux-en-Y gastric bypass (RYGB) and specifically the contribution of the concurrent peri-operative dietary restrictions, which may also alter glucose metabolism.

Materials and methods: In order to assess the differential contributions of diet and surgery to the mechanisms leading to the rapid improvement in diabetes after RYGB we enrolled 10 patients with type 2 diabetes scheduled to undergo RYGB. All patients underwent a 10-day inpatient supervised dietary intervention equivalent to the peri-operative diet (diet-only period), followed by, after a re-equilibration (washout) period, an identical period of pair-matched diet in conjunction with RYGB (diet and RYGB period). We conducted extensive metabolic assessments during a 6-hour mixed-meal challenge test, with stable isotope glucose tracer infusion performed before and after each intervention.

Results: Similar improvements in glucose levels, β-cell function, insulin sensitivity and post-meal hepatic insulin resistance were observed with both interventions. Both interventions led to significant reductions in fasting and postprandial acyl ghrelin. The diet-only intervention induced greater improvements in basal hepatic glucose output and post-meal gastric inhibitory polypeptide (GIP) secretion. The diet and RYGB intervention induced significantly greater increases in post-meal glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and glucagon levels.

Conclusions: Strict peri-operative dietary restriction is a main contributor to the rapid improvement in glucose metabolism after RYGB. The RYGB-induced changes in the incretin hormones GLP-1 and PYY probably play a major role in long-term compliance with such major dietary restrictions through central and peripheral mechanisms.

Keywords: diabetes remission; diet restriction; gastric bypass surgery; glycaemic control.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Glucose / metabolism
  • Caloric Restriction*
  • Diabetes Mellitus, Type 2 / complications
  • Diabetes Mellitus, Type 2 / metabolism*
  • Fasting / metabolism
  • Female
  • Gastric Bypass*
  • Gastric Inhibitory Polypeptide / metabolism
  • Ghrelin / metabolism
  • Glucagon / metabolism
  • Glucagon-Like Peptide 1 / metabolism
  • Humans
  • Insulin Resistance*
  • Insulin Secretion
  • Insulin-Secreting Cells / metabolism
  • Liver / metabolism
  • Male
  • Middle Aged
  • Obesity / complications
  • Obesity / diet therapy*
  • Obesity / metabolism
  • Obesity / surgery*
  • Peptide YY / metabolism
  • Postprandial Period
  • Remission Induction


  • Blood Glucose
  • Ghrelin
  • Peptide YY
  • Gastric Inhibitory Polypeptide
  • Glucagon-Like Peptide 1
  • Glucagon