Long-term changes in energy expenditure and body composition after massive weight loss induced by gastric bypass surgery.
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.
Das
Sai Krupa
SK
Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
Roberts
Susan B
SB
McCrory
Megan A
MA
Hsu
L K George
LK
Shikora
Scott A
SA
Kehayias
Joseph J
JJ
Dallal
Gerard E
GE
Saltzman
Edward
E
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
D020738:Leptin