G.L. Irwin, A.A.B. Cruz, C.J. Brush, A. Greene, S.J. Brooks, S. Trimberger, A.F. Brown

University of Idaho, Movement Sciences

It is estimated that 30 million Americans with a normal body mass index (BMI:18.5-24.9 kg/m2) also have excess body fat (≥25% males, ≥30% females), placing them at increased risk for cardiovascular disease, insulin resistance, and metabolic dysregulation. This hidden population is known as Normal Weight Obesity (NWO). Previous research has used various body composition techniques to determine NWO, making it challenging to determine the optimal technique to identify NWO and synthesize data among NWO research. PURPOSE: To determine levels of agreement between multiple body composition techniques and identify the prevalence of NWO across each body composition technique. METHODS: Participants (n=76; aged 18-25) visited the laboratory between 0500-1100, completed a demographic survey and seven body composition assessments using dual energy x-ray absorptiometry (DXA) and six different bioelectrical impedance analysis (BIA) scales (A, B, C, D, E, F). Pearson’s correlations were calculated between DXA and each BIA scale for body fat percentage. Bland-Altman analyses were conducted to assess the 95% limits of agreement (LOA) between DXA and each BIA scale. RESULTS: DXA reported 26.5% (n=9) of the sample as NWO, while the BIA scales reported the following: A: 2.4% (n=1), B: 2.4% (n=1), C: 0% (n=0), D: 62.3% (n=19), E: 20.6% (n=7), and F:14.7% (n=5). Moderate-to-strong relationships existed between DXA and each BIA scale (A: r=.73; B: r=.90,; C: r=.51; D: r=.88; E: .87; F: r=.91; all ps<0.001). Bland-Altman LOA (lower, upper) were A: -8.06, 12.27; B: -3.49, 9.83; C: 0.53, 5.51; D: 9.93, 5.51; E: -2.41, 11.03; F: -5.59, 11.17. CONCLUSION: Although moderate-to-strong relationships between DXA and BIA scales were observed for assessing body fat percentage, the classification of NWO varied greatly between scales. Compared to DXA, research-grade BIA scales (E & F) were more effective at identifying NWO whereas consumer-grade scales underpredicted (A-C) or overpredicted NWO (D).

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