Compared to dual-energy X-ray absorptiometry, bioelectrical impedance effectively monitors longitudinal changes in body composition in children and adolescents with obesity during a lifestyle intervention

Accurate and efficient body composition assessment is essential for diagnosing and monitoring childhood obesity in clinical and research settings. This study evaluated the agreement between bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) in assessing body composition and its changes during a long-term lifestyle intervention in children and adolescents with obesity. We hypothesized that BIA is comparable to DXA in tracking longitudinal changes in body composition in this population. The study included 92 children and adolescents 5 to 17 years of age (mean 10.5 ± 2.9 years) classified as obese at the time of measurement (body mass index-standard deviation score ≥ 2 SD). From January 1, 2014, to December 31, 2017, they participated in a lifestyle intervention at Randers Regional Hospital. Body composition was assessed using BIA and DXA at baseline and follow-up (mean 20.5 ± 9.3 months). Bland-Altman plots, correlation- and concordance analyses were used to evaluate the agreement between methods. Bland-Altman plots demonstrated wide limits of agreement without significant bias for longitudinal changes in fat mass (FM), FM%, fat-free mass (FFM), and FFM% (0.39 kg (CI -0.14, 0.93), -0.39% (CI -1.06, 0.26), -0.21 kg (CI -0.73, 0.31), and 0.39% (CI -0.27, 1.05), respectively). Correlations between methods for changes in FM, FM%, FFM, and FFM% were 0.93, 0.83, 0.88, and 0.83, respectively. In cross-sectional assessments, BIA underestimated FM and FM% and overestimated FFM and FFM% compared to DXA. Conclusively, BIA effectively monitors longitudinal changes in body composition at a group level in a pediatric population with obesity. However, caution is needed for individual assessments.