Gastric bypass increases energy expenditure in rats.
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.
Bueter
Marco
M
Department of Investigative Medicine, Hammersmith Hospital, Imperial College London, London, United Kingdom.
Löwenstein
Christian
C
Olbers
Torsten
T
Wang
Maggie
M
Cluny
Nina L
NL
Bloom
Stephen R
SR
Sharkey
Keith A
KA
Lutz
Thomas A
TA
le Roux
Carel W
CW
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