Body-composition changes with diet and exercise in obese women: a comparison of estimates from clinical methods and a 4-component model

• Published in: The American journal of clinical nutrition 1999-07, Vol.70 (1), p.5-12
• Main Authors: Evans, E.M, Saunders, M.J, Spano, M.A, Arngrimsson, S.A, Lewis, R.D, Cureton, K.J
• Format: Article
• Language: English
• Subjects: Absorptiometry, Photon; Adipose Tissue; Adult; anthropometric measurements; Anthropometry; Biological and medical sciences; Body Composition; body fat; Body Mass Index; Body Water; bone density; clinical aspects; density; Deuterium; Diet; Diet, Reducing; dieting; Electric Impedance; Energy Intake; estimation; evaluation; Exercise; Female; Humans; Investigative techniques, diagnostic techniques (general aspects); mathematical models; Medical sciences; Metabolic diseases; methodology; Miscellaneous. Technology; Obesity; Obesity - physiopathology; Obesity - therapy; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; physical activity; reduction; Skinfold Thickness; validity; water content; weight; Weight Loss; Women; X-radiation
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/70.1.5

Background: Most methods available to clinicians for estimating body-composition changes have been validated against estimates from densitometry, based on a 2-component (fat mass and fat-free mass) model. Objective: Estimates of changes in percentage body fat (%BF) from dual-energy X-ray absorptiometry (DXA), skinfold thicknesses (SFTs), bioelectrical impedance analysis (BIA), and body mass index (BMI: in kg/m(2)) were compared with estimates from a 4-component (fat, water, mineral, and protein) model (%BF(d,w,m)), a more accurate method. Design: Determinations of body density from hydrostatic weighing, body water from deuterium dilution, bone mineral and %BF from whole-body DXA, resistance from BIA, and anthropometric measures were made in 27 obese women (BMI: 31.1 +/- 4.9) assigned to 1 of 3 groups: control (C; n = 9), diet only (DO; n = 9), or diet plus aerobic exercise (DE; n = 9). Results: After the 16-wk intervention, changes in body mass (BM) averaged 0.5 +/- 2.0, -7.2 +/- 7.4, and -4.0 +/- 3.3 kg and changes in %BF(d,w,m) averaged 2.1 +/- 1.0%, -1.2 +/- 1.4%, and -2.4 +/- 1.6% in the C, DO, and DE groups, respectively. Compared with changes in %BF(d,w,m) the errors (SD of bias) for estimates of changes in %BF by DXA, BIA, SFTs, and BMI were similar (range: +/- 2.0-2.4% of BM). BIA, SFTs, and BMI provided unbiased estimates of decreases in %BF(d,w,m), but DXA overestimated decreases in %BF in the DO and DE groups. Conclusions: DXA, BIA, SFTs, and BMI are comparably accurate for evaluating body-composition changes induced by diet and exercise interventions; however, small changes in %BF may not be accurately detected by these clinical methods.