title: Roux-en-Y Gastric Bypass Surgery Increases Respiratory Quotient and Energy Expenditure during Food Intake.
abstract: OBJECTIVE
  The mechanisms determining long-term weight maintenance after Roux-en-Y gastric bypass (RYGB) remain unclear. Cross sectional studies have suggested that enhanced energy expenditure (EE) may play a significant role and the aim of this study was to reveal the impact of RYGB on each major component constituting total EE.
  
  
  METHODS
  Six obese female subjects, without other co-morbidities, were assessed before and at 10 days, 3 and 20 months after RYGB. Indirect calorimetry in a metabolic chamber was used to assess 24 h EE at each study visit. Other measurements included body composition by DEXA, gut hormone profiles and physical activity (PA) using high sensitivity accelerometers.
  
  
  RESULTS
  Median Body Mass Index decreased from 41.1 (range 39.1-44.8) at baseline to 28 kg/m2 (range 22.3-30.3) after 20 months (p<0.05). Lean tissue decreased from 55.9 (range 47.5-59.3) to 49.5 (range 41.1-54.9) kg and adipose tissue from 61 (range 56-64.6) to 27 (range 12-34.3) kg (both p<0.05). PA over 24 h did not change after surgery whereas 24 h EE and basal metabolic rate (BMR) decreased. EE after a standard meal increased after surgery when adjusted for total tissue (p<0.05). After an initial drop, RQ (respiratory quotient) had increased at 20 months, both as measured during 24 h and after food intake (p<0.05).
  
  
  CONCLUSIONS
  RYGB surgery up-regulates RQ and EE after food intake resulting in an increased contribution to total EE over 24 h when corrected for total tissue.
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska academy, University of Gothenburg. Department of Surgery, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Werling
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska academy, University of Gothenburg. Department of Surgery, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Fändriks
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska academy, University of Gothenburg. Department of Surgery, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden.
authors.forename: Torsten
authors.initials: T
authors.lastname: Olbers
authors.affiliation: Department of Surgery, Division of Visceral and Transplantation Surgery, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Bueter
authors.affiliation: Swedish Obese Subject's Secretariat, Institute of Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Sjöström
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska academy, University of Gothenburg. Department of Surgery, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Lönroth
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska academy, University of Gothenburg. Department of Surgery, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden.
authors.forename: Ville
authors.initials: V
authors.lastname: Wallenius
authors.affiliation: Gothia Forum, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Kaj
authors.initials: K
authors.lastname: Stenlöf
authors.affiliation: Department of Gastrosurgical Research and Education, Sahlgrenska academy, University of Gothenburg. Department of Surgery, Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden; Diabetes Complications Research Centre, Conway Institute, University College Dublin, Dublin, Ireland; Investigative Science, Imperial College London, London, United Kingdom.
authors.forename: Carel W
authors.initials: CW
authors.lastname: le Roux
mesh_terms: D000713:Anastomosis, Roux-en-Y / Q000009:adverse effects*; D001823:Body Composition; D004435:Eating; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D009765:Obesity / Q000601:surgery*; D012119:Respiration