title: Body composition in young female eating-disorder patients with severe weight loss and controls: evidence from the four-component model and evaluation of DXA.
abstract: OBJECTIVE
  Whether fat-free mass (FFM) and its components are depleted in eating-disorder (ED) patients is uncertain. Dual energy X-ray absorptiometry (DXA) is widely used to assess body composition in pediatric ED patients; however, its accuracy in underweight populations remains unknown. We aimed (1) to assess body composition of young females with ED involving substantial weight loss, relative to healthy controls using the four-component (4C) model, and (2) to explore the validity of DXA body composition assessment in ED patients.
  
  
  METHODS
  Body composition of 13 females with ED and 117 controls, aged 10-18 years, was investigated using the 4C model. Accuracy of DXA for estimation of FFM and fat mass (FM) was tested using the approach of Bland and Altman.
  
  
  RESULTS
  Adjusting for age, height and pubertal stage, ED patients had significantly lower whole-body FM, FFM, protein mass (PM) and mineral mass (MM) compared with controls. Trunk and limb FM and limb lean soft tissue were significantly lower in ED patients. However, no significant difference in the hydration of FFM was detected. Compared with the 4C model, DXA overestimated FM by 5 ± 36% and underestimated FFM by 1 ± 9% in ED patients.
  
  
  CONCLUSIONS
  Our study confirms that ED patients are depleted not only in FM but also in FFM, PM and MM. DXA has limitations for estimating body composition in individual young female ED patients.
authors.affiliation: Childhood Nutrition Research Centre, UCL Institute of Child Health, London, UK.
authors.forename: J C K
authors.initials: JC
authors.lastname: Wells
authors.affiliation: Childhood Nutrition Research Centre, UCL Institute of Child Health, London, UK.
authors.forename: D
authors.initials: D
authors.lastname: Haroun
authors.affiliation: Childhood Nutrition Research Centre, UCL Institute of Child Health, London, UK.
authors.forename: J E
authors.initials: JE
authors.lastname: Williams
authors.affiliation: Department of Psychological Medicine, Child and Adolescent Mental Health, Great Ormond Street Hospital, London, UK.
authors.forename: D
authors.initials: D
authors.lastname: Nicholls
authors.affiliation: Childhood Nutrition Research Centre, UCL Institute of Child Health, London, UK.
authors.forename: T
authors.initials: T
authors.lastname: Darch
authors.affiliation: Developmental Biology and Cancer Programme, UCL Institute of Child Health, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Eaton
authors.affiliation: Childhood Nutrition Research Centre, UCL Institute of Child Health, London, UK.
authors.forename: M S
authors.initials: MS
authors.lastname: Fewtrell
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D001823:Body Composition; D015992:Body Mass Index; D016022:Case-Control Studies; D002648:Child; D019317:Evidence-Based Medicine; D001068:Feeding and Eating Disorders / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008962:Models, Theoretical; D013851:Thinness / Q000503:physiopathology*; D015431:Weight Loss