title: Increased postprandial energy expenditure may explain superior long term weight loss after Roux-en-Y gastric bypass compared to vertical banded gastroplasty.
abstract: OBJECTIVE
  Gastric bypass results in greater weight loss than Vertical banded gastroplasty (VBG), but the underlying mechanisms remain unclear. In addition to effects on energy intake the two bariatric techniques may differentially influence energy expenditure (EE). Gastric bypass in rats increases postprandial EE enough to result in elevated EE over 24 hours. This study aimed to investigate alterations in postprandial EE after gastric bypass and VBG in humans.
  
  
  METHODS
  Fourteen women from a randomized clinical trial between gastric bypass (n = 7) and VBG (n = 7) were included. Nine years postoperatively and at weight stability patients were assessed for body composition and calorie intake. EE was measured using indirect calorimetry in a respiratory chamber over 24 hours and focused on the periods surrounding meals and sleep. Blood samples were analysed for postprandial gut hormone responses.
  
  
  RESULTS
  Groups did not differ regarding body composition or food intake either preoperatively or at study visit. Gastric bypass patients had higher EE postprandially (p = 0.018) and over 24 hours (p = 0.048) compared to VBG patients. Postprandial peptide YY (PYY) and glucagon like peptide 1 (GLP-1) levels were higher after gastric bypass (both p<0.001).
  
  
  CONCLUSIONS
  Gastric bypass patients have greater meal induced EE and total 24 hours EE compared to VBG patients when assessed 9 years postoperatively. Postprandial satiety gut hormone responses were exaggerated after gastric bypass compared to VBG. Long-term weight loss maintenance may require significant changes in several physiological mechanisms which will be important to understand if non-surgical approaches are to mimic the effects of bariatric surgery.
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska Academy, University of Gothenburg, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden. malin.werling@gmail.com
authors.forename: Malin
authors.initials: M
authors.lastname: Werling
authors.forename: Torsten
authors.initials: T
authors.lastname: Olbers
authors.forename: Lars
authors.initials: L
authors.lastname: Fändriks
authors.forename: Marco
authors.initials: M
authors.lastname: Bueter
authors.forename: Hans
authors.initials: H
authors.lastname: Lönroth
authors.forename: Kaj
authors.initials: K
authors.lastname: Stenlöf
authors.forename: Carel W
authors.initials: CW
authors.lastname: le Roux
mesh_terms: D050154:Adiposity; D000328:Adult; D015992:Body Mass Index; D004734:Energy Metabolism; D005260:Female; D005500:Follow-Up Studies; D015390:Gastric Bypass; D015391:Gastroplasty; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity; D009765:Obesity / Q000378:metabolism / Q000601:surgery*; D019518:Postprandial Period; D016032:Randomized Controlled Trials as Topic; D056152:Respiratory Rate; D016896:Treatment Outcome; D015431:Weight Loss