title: Thermogenic changes after gastric bypass, adjustable gastric banding or diet alone.
abstract: BACKGROUND
  The mechanisms by which bariatric surgery achieves weight loss (WL) are under scrutiny. We assessed changes in resting energy expenditure (REE) after gastric bypass (RYGB) and gastric banding (AGB) to determine if changes in REE are associated with WL and type of surgery.
  
  
  METHODS
  Three groups of morbidly obese patients were studied: RYGB (n = 12), AGB (n = 8), and a control group that underwent caloric restriction alone (Diet, n = 10). Studies were performed at baseline and after 14 days in all groups and 6 months after RYGB and AGB. REE (kcal/day) was measured by indirect calorimetry and adjusted for body weight (Wt-REE), and lean body mass by dual-energy X-ray absorptiometry (LBM-REE).
  
  
  RESULTS
  At baseline, REE did not differ significantly among groups (RYGB = 2,114 ± 337, AGB = 1,837 ± 154, Diet = 2,091 ± 363 kcal/day, P = .13). After 14 days, the groups had similar percent excess WL (%EWL). Neither Wt-REE nor LBM-REE changed significantly in any group. After 6 months %EWL was 49 ± 10% after RYGB and 21 ± 11% after AGB (P < .01); RYGB patients had greater increase in the percent of weight that was LBM (RYGB = 7.9 ± 3.0 vs. AGB = 1.6 ± 1.5%, P < .01). Wt-REE increased significantly only after RYGB (+2.58 ± 1.51 kcal/kg/day, P < .01). There was a significant correlation between changes in Wt-REE and %EWL (r = 0.670, P = .003).
  
  
  CONCLUSIONS
  The increase in Wt-REE may be a factor supporting WL after RYGB.
authors.affiliation: Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI; Department of Surgery, University of California San Francisco, San Francisco, CA; Department of Surgery, Paracelsus Medical University, Salzburg, Austria.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Rabl
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, CA.
authors.forename: Madhu N
authors.initials: MN
authors.lastname: Rao
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, CA; Touro University-California, Vallejo, CA.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Schwarz
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, CA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Mulligan
authors.affiliation: Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI; Department of Surgery, University of California San Francisco, San Francisco, CA. Electronic address: campos@surgery.wisc.edu.
authors.forename: Guilherme M
authors.initials: GM
authors.lastname: Campos
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D002153:Calorimetry, Indirect; D004038:Diet, Reducing; D005260:Female; D005500:Follow-Up Studies; D015390:Gastric Bypass; D015391:Gastroplasty; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000178:diet therapy / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D015431:Weight Loss / Q000502:physiology*