title: Long-term changes in energy expenditure and body composition after massive weight loss induced by gastric bypass surgery.
abstract: BACKGROUND
  Little is known about the determinants of individual variability in body weight and fat loss after gastric bypass surgery or about the effects of massive weight loss induced by this surgery on energy requirements.
  
  
  OBJECTIVE
  The objectives were to determine changes in energy expenditure and body composition with weight loss induced by gastric bypass surgery and to identify presurgery predictors of weight loss.
  
  
  METHODS
  Thirty extremely obese women and men with a mean (+/- SD) age of 39.0 +/- 9.6 y and a body mass index (BMI; in kg/m(2)) of 50.1 +/- 9.3 were tested longitudinally under weight-stable conditions before surgery and after weight loss and stabilization (14 +/- 2 mo). Total energy expenditure (TEE), resting energy expenditure (REE), body composition, and fasting leptin were measured.
  
  
  RESULTS
  Subjects lost 53.2 +/- 22.2 kg body weight and had significant decreases in REE (-2.4 +/- 1.0 MJ/d; P < 0.001) and TEE (-3.6 +/- 2.5 MJ/d; P < 0.001). Changes in REE were predicted by changes in fat-free mass and fat mass. The average physical activity level (TEE/REE) was 1.61 at both baseline and follow-up (P = 0.98). Weight loss was predicted by baseline fat mass and BMI but not by any energy expenditure variable or leptin. Measured REE at follow-up was not significantly different from predicted REE.
  
  
  CONCLUSIONS
  TEE and REE decreased by 25% on average after massive weight loss induced by gastric bypass surgery. REE changes were predicted by loss of body tissue; thus, there was no significant long-term change in energy efficiency that would independently promote weight regain.
authors.affiliation: Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
authors.forename: Sai Krupa
authors.initials: SK
authors.lastname: Das
authors.forename: Susan B
authors.initials: SB
authors.lastname: Roberts
authors.forename: Megan A
authors.initials: MA
authors.lastname: McCrory
authors.forename: L K George
authors.initials: LK
authors.lastname: Hsu
authors.forename: Scott A
authors.initials: SA
authors.lastname: Shikora
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Kehayias
authors.forename: Gerard E
authors.initials: GE
authors.lastname: Dallal
authors.forename: Edward
authors.initials: E
authors.lastname: Saltzman
mesh_terms: D000328:Adult; D001823:Body Composition; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D020738:Leptin / Q000097:blood; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology* / Q000601:surgery*; D011184:Postoperative Period; D015431:Weight Loss
chemical_list: D020738:Leptin