title: Body composition and energy metabolism following Roux-en-Y gastric bypass surgery.
abstract: Roux-en-Y gastric bypass (RYGB) surgery has become an accepted treatment for excessive obesity. We conducted a longitudinal study to assess regional body composition, muscle proteolysis, and energy expenditure before RYGB, and 6 and 12 months after RYGB. Whole-body and regional fat mass (FM) and lean mass (LM) were assessed via dual energy X-ray absorptiometry (DXA), and myofibrillar protein degradation was estimated by urinary 3-methylhistidine (3-MeH) in 29 subjects. Energy expenditure and substrate oxidation were also determined using a whole-room, indirect calorimeter in 12 of these subjects. LM loss constituted 27.8 +/- 10.2% of total weight loss achieved 12 months postoperatively, with the majority of LM loss (18 +/- 6% of initial LM) occurring in the first 6 months following RYGB. During this period, the trunk region contributed 66% of whole-body LM loss. LM loss occurred in the first 6 months after RYGB despite decreased muscle protein breakdown, as indicated by a decrease in 3-MeH concentrations and muscle fractional breakdown rates. Sleep energy expenditure (SEE) decreased from 2,092 +/- 342 kcal/d at baseline to 1,495 +/- 190 kcal/day at 6 months after RYGB (P < 0.0001). Changes in both LM and FM had an effect on the reduction in SEE (P < 0.001 and P = 0.005, respectively). These studies suggest that loss of LM after RYGB is significant and strategies to maintain LM after surgery should be explored.
authors.affiliation: Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
authors.forename: Robyn A
authors.initials: RA
authors.lastname: Tamboli
authors.forename: H Ayesha
authors.initials: HA
authors.lastname: Hossain
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Marks
authors.forename: Aaron W
authors.initials: AW
authors.lastname: Eckhauser
authors.forename: John A
authors.initials: JA
authors.lastname: Rathmacher
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Phillips
authors.forename: Maciej S
authors.initials: MS
authors.lastname: Buchowski
authors.forename: Kong Y
authors.initials: KY
authors.lastname: Chen
authors.forename: Naji N
authors.initials: NN
authors.lastname: Abumrad
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000293:Adolescent; D000328:Adult; D000368:Aged; D001823:Body Composition; D001825:Body Fluid Compartments / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008762:Methylhistidines / Q000652:urine; D008875:Middle Aged; D009124:Muscle Proteins / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism*; D009767:Obesity, Morbid / Q000378:metabolism* / Q000503:physiopathology / Q000601:surgery; D011859:Radiography; D015431:Weight Loss; D055815:Young Adult
chemical_list: D008762:Methylhistidines; D009124:Muscle Proteins; C028118:3-methylhistidine