(1) Background: The determination of body composition is an important method to investigate patients with obesity and to evaluate the efficacy of individualized medical interventions. Bioelectrical impedance-based methods are non-invasive and widely applied but need to be validated for their use in young patients with obesity. (2) Methods: We compiled data from three independent studies on children and adolescents with obesity, measuring body composition with two bioelectrical impedance-based devices (TANITA and BIACORPUS). For a small patient group, additional data were collected with air displacement plethysmography (BOD POD) and dual-energy X-ray absorptiometry (DXA). (3) Results: Our combined data on 123 patients (age: 6–18 years, body mass index (BMI): 21–59 kg/m²) and the individual studies showed that TANITA and BIACORPUS yield significantly different results on body composition, TANITA overestimating body fat percentage and fat mass relative to BIACORPUS and underestimating fat-free mass (p < 0.001 for all three parameters). A Bland–Altman plot indicated little agreement between methods, which produce clinically relevant differences for all three parameters. We detected gender-specific differences with both methods, with body fat percentage being lower (p < 0.01) and fat-free mass higher (p < 0.001) in males than females. (4) Conclusions: Both bioelectrical impedance-based methods provide significantly different results on body composition in young patients with obesity and thus cannot be used interchangeably, requiring adherence to a specific device for repetitive measurements to ascertain comparability of data.

Summary Background This study determined to what extent the underpinning of physiotherapeutic interventions with the evidence-based motivational psychological concept of the self-determination theory (SDT) by Ryan and Deci can increase motivation and enjoyment of movement in obese adolescents. Methods In this study 12 obese adolescents aged 14–18 years were offered a targeted group-specific sports program including a home exercise program of 8 weeks. The group leaders were trained in the SDT and supported to integrate motivational aspects. A SDT-based questionnaire by Kohake and Lehnert was used to evaluate motivational interventions. Results In total, seven (58%) patients finished the study. In the before-after comparison there were little changes in motivation. Results showed that contrary to expectations the motivation of the obese adolescents to move and to participate in the study was generally high. In the study, more internalized forms of motivation dominated, the highest quality form of motivation. Conclusion Digital technologies could be a successful way to further increase motivation and compliance of our target group. This MotiMove study is a basis for future research programs and empower physiotherapists and movement experts to develop and implement training programs for obese adolescents and children.

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