Physical Activity Status and Adiposity-Related Morphological Risk in Children: Differences in Anthropometric, Body Composition, and Somatotype Indicators

Background/Objectives: Physical inactivity represents one of the most critical public health challenges of recent decades, particularly in pediatric populations. Therefore, this study aimed to evaluate differences in adiposity-related morphological risk indicators between physically active and inactive children by simultaneously integrating anthropometric measures, five-component body composition, and somatotype analysis. Methods: This cross-sectional study included 126 children aged 6–9 years (56 girls and 70 boys). Physical activity status was determined using the Physical Activity Questionnaire for Older Children. Anthropometric indicators included BMI, waist circumference, waist-to-hip ratio, waist-to-height ratio, and conicity index. Adipose and muscle mass, fat mass index, and adipose-to-muscle ratio were estimated using Kerr’s five-component model, and somatotype was assessed using the Heath-Carter method. Results: Inactive children showed higher body mass index (BMI), waist circumference, waist-to-hip ratio, waist-to-height ratio, conicity index, adipose mass, fat mass index, sum of skinfolds, and endomorphy, together with lower ectomorphy, than active children (all p < 0.05). Sex-stratified analyses showed that these differences were broader and generally larger among boys. Age-adjusted interaction models also indicated more pronounced active–inactive differences in boys for several central and total adiposity indicators. Conclusions: Physical inactivity was associated with a less favorable adiposity-related morphological profile in children aged 6–9 years, particularly among boys. These findings support complementing BMI with central adiposity indicators, body composition measures, and somatotype analysis in pediatric and school-based assessments, potentially supporting earlier identification of children with unfavorable morphological profiles.