title: Measurement of body composition changes during weight loss in obese men using multi-frequency bioelectrical impedance analysis and multi-compartment models.
abstract: BACKGROUND
  The accurate measurement of changes in body composition is important to assess the contribution of fat and fat free mass to total body mass change as a measure of the effectiveness of weight loss programmes. Bioelectrical impedance spectroscopy (BIS) is a rapid and non-invasive technique which could be applied to assess body composition changes. The aim of the study was to evaluate the accuracy of the BIS for the measurement of fat mass (FM), total body water (TBW) and extracellular water (ECW) changes induced by different degrees of caloric deficit in obese men.
  
  
  METHODS
  Three groups of six, obese men participated in either (i) a total fast (for 6 days); (ii) a VLCD (2.5 MJ/day for 3 weeks); or (iii) LCD (5.2 MJ/day for 6 weeks). FM was measured using a 4-compartment (4-C) model. TBW and ECW were determined by dilution methods, respectively. TBW, ECW and FM were also assessed with BIS.
  
  
  RESULTS
  Body weight loss in the fasting group was 6.0 ± 1.3 kg over 6 days; the VLCD group lost 9.2 ± 1.2 kg over 21 days and the LCD group lost 12.6 ± 2.4 kg over 42 days. BIS underestimated FM changes (bias = -3.3 ± 3.8 kg) and overestimated changes in TBW and ECW by +1.8 ± 4.8 kg and +2.3 ± 6.4 kg, respectively. The measurement error was consistently larger in the fasting group and the magnitude of the bias interacted significantly with the rate of weight loss.
  
  
  CONCLUSIONS
  Rapid weight loss affects the accuracy of the BIS in detecting changes in body composition. A careful interpretation of the results is needed when sizable changes in body water compartments occurs.
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Johnstone
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Faber
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Eileen R
authors.initials: ER
authors.lastname: Gibney
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Lobley
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: R James
authors.initials: RJ
authors.lastname: Stubbs
authors.affiliation: Human Nutrition Research Centre, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK. Electronic address:mario.siervo@ncl.ac.uk.
authors.forename: Mario
authors.initials: M
authors.lastname: Siervo
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001823:Body Composition / Q000502:physiology; D001834:Body Water / Q000378:metabolism; D017097:Electric Impedance; D005110:Extracellular Space / Q000378:metabolism*; D005215:Fasting / Q000502:physiology; D006801:Humans; D007201:Indicator Dilution Techniques; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009765:Obesity / Q000378:metabolism* / Q000503:physiopathology; D015203:Reproducibility of Results; D014867:Water; D015431:Weight Loss / Q000502:physiology; D055815:Young Adult
chemical_list: D014867:Water