Assessment of Body Composition in Obese Pediatric Patients: a Method Comparison

BackgroundThe determination of body composition is an important method to investigate obese patients and to evaluate the efficacy of medical interventions. Bioelectrical impedance-based methods are convenient, non-invasive and widely applied for this purpose, but need to be validated for their use in young obese patients.MethodsWe compiled data from three independent studies on different aspects of obesity in children and adolescents, measuring body composition with two bioelectrical impedance-based devices (TANITA and BIA). Further, for a small patient group additional data were collected with air displacement plethysmography (BOD POD) and DXA.ResultsBoth, the combined data of the entire study population of 123 patients (age: 6-18 years, BMI: 21-59 kg/m²) and the data of each individual study, showed that TANITA and BIA yield significantly different results on body composition, with TANITA overestimating body fat percentage and fat mass relative to BIA and underestimating fat-free mass (p < 0.001 for all three parameters). A Bland-Altman plot revealed that both methods show little agreement and produce clinically relevant differences for all three parameters. In addition, we detected gender-specific differences with both methods, body fat percentage being significantly lower (p < 0.01) and fat-free mass significantly higher (p < 0.001) in males than females. A comparison of bioelectrical impedance-based methods with BOD POD and DXA on a small patient group indicated no significant difference between methods.ConclusionsBoth bioelectrical impedance-based methods provide significantly different results on body composition in young obese patients and the data thus cannot be used interchangeably. Routine clinical practice may nonetheless use these devices but must adhere to a specific device for repetitive measurements to ascertain comparability of data.Trial registration: Study#2, Children`s KNEEs study, ClinicalTrials NCT02545764. Registered 10 September 2015, https://clinicaltrials.gov/ct2/show/results/NCT02545764