Longitudinal assessment of body composition and physical activity in children with and without obesity from early pubescence to young adulthood

Introduction: Childhood obesity is one of the most pressing public health concerns in the United States and increases the risk of adulthood obesity. Although regular exercise is central to obesity prevention and treatment, the relationship between obesity and physical activity engagement during growth remains poorly defined. Therefore, the purpose of this study was to determine the longitudinal changes in body composition and self-reported physical activity in children with and without obesity from early pubescence to young adulthood. Methods: Twenty-three children (ages 8–12 at baseline; Tanner stage ≤3, 6 females, 17 males) were followed for 7.2 ± 0.3 years. At baseline, there were 17 children with obesity (CWO, BMI ≥95th percentile, 24% female) and 6 children without obesity (CWOO, BMI 15th–85th percentile, 33% female). Body composition was assessed by dual-energy X-ray absorptiometry (DEXA), and self-reported physical activity was assessed by the Physical Activity Questionnaire for Children (PAQ-C score). Results: Participants were 10.5 ± 1.0 years old at baseline and 17.4 ± 1.1 years old at follow-up. Body mass index (BMI) was greater in CWO at baseline (98th percentile; 27 ± 4 kg/m 2 ) than in CWOO (57th percentile; 18 ± 2 kg/m 2 , P < 0.001) and remained higher at follow up (CWO: 93rd percentile; 34 ± 8 kg/m 2 vs. CWOO: 60th percentile; 23 ± 3 kg/m 2 , P = 0.003). Throughout the study, the fat mass increase per year was ~2.6 times greater in CWO (3.61 ± 1.11 kg/year) than in CWOO (1.38 ± 0.54 kg/year, P < 0.001). PAQ-C scores did not differ between groups at baseline (CWO: 2.8 ± 0.6 vs. CWOO: 2.6 ± 0.6, P = 0.228) or follow up (CWO: 1.8 ± 0.6 vs. CWOO: 1.9 ± 0.6, P = 0.955). However, PAQ-C scores significantly decreased over time in both groups (P < 0.001) with 22 of 23 participants showing reduced physical activity. Larger declines in PAQ-C from baseline to follow up were associated with greater gains in fat mass relative to total mass (r = -0.445, P = 0.003). Conclusion: Our preliminary data are the first to directly show that early pubertal obesity persisted during growth and progressed toward adulthood obesity. The marked increase in fat mass was, at least in part, linked to declining physical activity, and this decline occurred regardless of initial obesity status. This indicates that lower engagement in physical activity during growth is a broad pattern rather than an obesity-specific phenomenon. Overall, our findings underscore the need to promote physical activity throughout childhood to mitigate long-term obesity risk. Funding source: This study was supported by NIH Grant R01 HL136643, King Charitable Foundation Trust, Susan Lay Atwell Annuity Trust for Pulmonary Research, Cain Foundation, and Texas Health Presbyterian Hospital Dallas. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.