title: Gastric bypass increases energy expenditure in rats.
abstract: OBJECTIVE
  Mechanisms underlying weight loss maintenance after gastric bypass are poorly understood. Our aim was to examine the effects of gastric bypass on energy expenditure in rats.
  
  
  METHODS
  Thirty diet-induced obese male Wistar rats underwent either gastric bypass (n = 14), sham-operation ad libitum fed (n = 8), or sham-operation body weight-matched (n = 8). Energy expenditure was measured in an open circuit calorimetry system.
  
  
  RESULTS
  Twenty-four-hour energy expenditure was increased after gastric bypass (4.50 +/- 0.04 kcal/kg/h) compared with sham-operated, ad libitum fed (4.29 +/- 0.08 kcal/kg/h) and sham-operated, body weight-matched controls (3.98 +/- 0.10 kcal/kg/h, P < .001). Gastric bypass rats showed higher energy expenditure during the light phase than sham-operated control groups (sham-operated, ad libitum fed: 3.63 +/- 0.04 kcal/kg/h vs sham-operated, body weight-matched: 3.42 +/- 0.05 kcal/kg/h vs bypass: 4.12 +/- 0.03 kcal/kg/h, P < .001). Diet-induced thermogenesis was elevated after gastric bypass compared with sham-operated, body weight-matched controls 3 hours after a test meal (0.41% +/- 1.9% vs 10.5% +/- 2.0%, respectively, P < .05). The small bowel of gastric bypass rats was 72.1% heavier because of hypertrophy compared with sham-operated, ad libitum fed rats (P < .0001).
  
  
  CONCLUSIONS
  Gastric bypass in rats prevented the decrease in energy expenditure after weight loss. Diet-induced thermogenesis was higher after gastric bypass compared with body weight-matched controls. Raised energy expenditure may be a mechanism explaining the physiologic basis of weight loss after gastric bypass.
authors.affiliation: Department of Investigative Medicine, Hammersmith Hospital, Imperial College London, London, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Bueter
authors.forename: Christian
authors.initials: C
authors.lastname: Löwenstein
authors.forename: Torsten
authors.initials: T
authors.lastname: Olbers
authors.forename: Maggie
authors.initials: M
authors.lastname: Wang
authors.forename: Nina L
authors.initials: NL
authors.lastname: Cluny
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Bloom
authors.forename: Keith A
authors.initials: KA
authors.lastname: Sharkey
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Lutz
authors.forename: Carel W
authors.initials: CW
authors.lastname: le Roux
mesh_terms: D000818:Animals; D001823:Body Composition; D002153:Calorimetry, Indirect; D004195:Disease Models, Animal; D004435:Eating; D004734:Energy Metabolism; D015390:Gastric Bypass; D006984:Hypertrophy; D007421:Intestine, Small / Q000473:pathology / Q000601:surgery; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000378:metabolism / Q000503:physiopathology / Q000601:surgery*; D017440:Photoperiod; D011659:Pulmonary Gas Exchange; D051381:Rats; D017208:Rats, Wistar; D022722:Thermogenesis; D013997:Time Factors; D015431:Weight Loss