title: Determinants of changes in muscle mass after bariatric surgery.
abstract: OBJECTIVE
  The constituents of weight loss following bariatric surgery are poorly known. There is an expectation of a limited loss of lean body mass (LBM), and a significant loss of fat mass (FM) as well as muscle mass (MM), which could lead to functional loss and metabolic impairment. This prospective study analysed the determinants of MM changes after Roux-en-Y gastric bypass and sleeve gastrectomy.
  
  
  METHODS
  The study cohort comprised 114 consecutive candidates for bariatric surgery referred to a bariatric surgery centre. Using DEXA, the subjects' body composition was assessed before, and three and 12 months (n=92) after, the surgery, along with their biological status. The main study outcome was changes in MM.
  
  
  RESULTS
  At three months, patients had lost 20.3 kg, made up of 41% LBM and 59% FM. The contribution of MM to weight loss was 16.4%. Cluster analysis showed that 52 patients lost<15% of their weight as MM, while 62 patients lost>15% as MM. At 12 months, patients had lost 37 kg, made up of 70% FM and 30% LBM. At this time, only 27 patients lost>15% of their weight as MM. The determinants that were negatively and independently associated with MM changes at three months were FM loss and changes in glycaemia and thyroid-stimulating hormone ([TSH]; thyrotropin) before surgery, whereas change in glycaemia was the only 12-month determinant associated with MM changes.
  
  
  CONCLUSIONS
  Two phenotypes - one with muscle wasting and the other with acceptable muscle loss - with a threshold of 15% and very few predictive factors were identified by this study.
authors.affiliation: Nutrition Unit, Endocrinology Department, CHU Larrey, 31059 Toulouse cedex 09, France. Electronic address: vaurscharlotte@yahoo.fr.
authors.forename: C
authors.initials: C
authors.lastname: Vaurs
authors.affiliation: UMR 1027, Inserm, Epidemiology Department, université Toulouse 3, CHU de Toulouse, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Diméglio
authors.affiliation: Digestive Surgery Department, clinique des Cèdres, Cornebarrieu, France.
authors.forename: L
authors.initials: L
authors.lastname: Charras
authors.affiliation: Digestive Surgery Department, clinique des Cèdres, Cornebarrieu, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Anduze
authors.affiliation: Digestive Surgery Department, CHU of Toulouse, Toulouse, France.
authors.forename: M
authors.initials: M
authors.lastname: Chalret du Rieu
authors.affiliation: Nutrition Unit, Endocrinology Department, CHU Larrey, 31059 Toulouse cedex 09, France; UMR 1027, Inserm, Epidemiology Department, université Toulouse 3, CHU de Toulouse, Toulouse, France.
authors.forename: P
authors.initials: P
authors.lastname: Ritz
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D050110:Bariatric Surgery / Q000009:adverse effects*; D015992:Body Mass Index; D016000:Cluster Analysis; D015331:Cohort Studies; D003131:Combined Modality Therapy; D004038:Diet, Reducing / Q000009:adverse effects; D005260:Female; D005602:France; D006801:Humans; D059012:Lost to Follow-Up; D008297:Male; D008875:Middle Aged; D024510:Muscle Development; D009135:Muscular Diseases / Q000209:etiology* / Q000517:prevention & control; D009767:Obesity, Morbid / Q000178:diet therapy / Q000601:surgery*; D011183:Postoperative Complications / Q000209:etiology* / Q000517:prevention & control; D011446:Prospective Studies; D012017:Referral and Consultation; D013531:Surgicenters; D015431:Weight Loss
keywords: Body composition; Glycaemia; Muscle mass; Obesity surgery