Body composition and energy metabolism following Roux-en-Y gastric bypass surgery

Obesity (Silver Spring). 2010 Sep;18(9):1718-24. doi: 10.1038/oby.2010.89. Epub 2010 Apr 22.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adipose Tissue / diagnostic imaging
  • Adolescent
  • Adult
  • Aged
  • Body Composition*
  • Body Fluid Compartments / metabolism*
  • Energy Metabolism / physiology*
  • Female
  • Gastric Bypass*
  • Humans
  • Longitudinal Studies
  • Male
  • Methylhistidines / urine
  • Middle Aged
  • Muscle Proteins / metabolism*
  • Myofibrils / metabolism*
  • Obesity, Morbid / metabolism*
  • Obesity, Morbid / physiopathology
  • Obesity, Morbid / surgery
  • Radiography
  • Weight Loss
  • Young Adult


  • Methylhistidines
  • Muscle Proteins
  • 3-methylhistidine