title: Agreement of bioelectrical impedance with dual-energy X-ray absorptiometry and MRI to estimate changes in body fat, skeletal muscle and visceral fat during a 12-month weight loss intervention.
abstract: The aim of the present study was to analyse the agreement of bioelectrical impedance analysis (BIA) compared with dual-energy X-ray absorptiometry (DXA) and MRI in estimating body fat, skeletal muscle and visceral fat during a 12-month weight loss intervention. A total of nineteen obese adults (twelve females, seven males) aged 20·2-48·6 years, mean BMI 34·6 (SE 0·6) kg/m², participated in the study. Body fat, skeletal muscle and visceral fat index were measured by BIA (Omron BF-500; Omron Medizintechnik) and compared with DXA (body fat and skeletal muscle) at baseline, 5 and 12 months, and with MRI (visceral fat) at baseline and 5 months. The subjects lost 8·9 (SE 1·8) kg (9·0 (SE 1·7) %) of body weight during the 12-month intervention. BIA, as compared to DXA, accurately assessed loss of fat (7·0 (SE 1·5) v. 7·0 (SE 1·4) kg, P= 0·94) and muscle (1·0 (SE 0·2) v. 1·4 (SE 0·3) kg, P= 0·18). While body fat was similar by the two methods, skeletal muscle was underestimated by 1-2 kg using BIA at each time point. Compared to MRI, BIA overestimated visceral fat, especially in males. BIA and DXA showed high correlations for kg fat, both cross-sectionally and longitudinally (r 0·91-0·99). BIA, compared with DXA and MRI, detected kg muscle and visceral fat more accurately cross-sectionally (r 0·77-0·87 and r 0·40-0·78, respectively) than their changes longitudinally (r 0·24-0·61 and r 0·46, respectively). BIA is at its best when assessing the amount or changes in fat mass. It is a useful method for measuring skeletal muscle, but limited in its ability to measure visceral fat.
authors.affiliation: Obesity Research Unit, Department of Medicine, Division of Endocrinology, Helsinki University Central Hospital, University of Helsinki, Biomedicum 1, Haartmaninkatu 8, PO Box 700, FIN-00029 HUCH, Finland. kirsi.pietilainen@helsinki.fi
authors.forename: Kirsi H
authors.initials: KH
authors.lastname: Pietiläinen
authors.forename: Sanna
authors.initials: S
authors.lastname: Kaye
authors.forename: Anna
authors.initials: A
authors.lastname: Karmi
authors.forename: Laura
authors.initials: L
authors.lastname: Suojanen
authors.forename: Aila
authors.initials: A
authors.lastname: Rissanen
authors.forename: Kirsi A
authors.initials: KA
authors.lastname: Virtanen
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000273:Adipose Tissue / Q000502:physiology*; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D001825:Body Fluid Compartments / Q000502:physiology; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D050152:Intra-Abdominal Fat / Q000502:physiology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D009765:Obesity / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D015431:Weight Loss; D061217:Weight Reduction Programs; D055815:Young Adult