Linking metabolic syndrome and physical fitness in children with obesity: a cross-sectional study from the PODiaCar project

Aim: Paediatric obesity is a major public health concern, as recognized by the World Health Organization. Metabolic syndrome (MetS), associated with increased cardiovascular (CV) morbidity and mortality, affects approximately 29.2% of children with obesity. Physical fitness (PF) is a key indicator of long-term health, influencing CV risk and overall mortality. However, few studies have examined its association with MetS. This study aims to analyze the relationship between PF and MetS in children with obesity. Methods: We conducted a cross-sectional study evaluating 55 children with obesity (11.96 ± 2.35 years; 21 [38%] girls; mean BMI 29.5 ± 4.81 kg/m2 and BMI z-score 3.15 ± 0.78). Physical fitness was assessed through three functional tests: i) 6-minute walking test (6MWT), ii) standing broad jump (SBJ), and iii) 4×10 m shuttle run test (SHT). MetS z-score assesses MetS, using sex-specific formulas (cut-off > 0.75). Between 8:30 and 9:00 a.m. a fasting blood sample was collected and analyzed that morning for total cholesterol, HDL-C, triglycerides, fasting glucose (FG), and insulin. Insulin resistance was estimated using HOMA-IR and TyG index. Logistic regression was used to calculate adjusted odds ratios (OR) for MetS based on PF levels, while linear regression assessed associations between PF, MetS z-score, and its components. Results: In both sexes, the SBJ test inversely correlates with MetS odds, independent of age (OR: 0.18, 95%, CI: 0.04–0.53). Conversely, neither the 6MWT nor the SHT were related to the odds of MetS. When analyzing the relation between MetS z-score, its components and PF, the SBJ showed an inverse significant association (BMI z-score: β=-0.528; SBP: β=-0.397; MetS z-score: β=-0.299; all p < 0.05) with all components, except for HDL, FG and triglycerides (respectively β=0.335, β=0.429 and β=0.354), which were positively associated. The SHT was associated with BMI z-score (β=0.419), systolic blood pressure (β=0.419), and FG (β=-0.331; all P < 0.05), while the 6MWT was inversely related to BMI z-score (β=0.295; P < 0.05). Conclusions: Our findings highlight an inverse relationship between PF and MetS, particularly concerning lower limb strength, as assessed by the SBJ. These results highlight the importance of incorporating PF assessments into the clinical evaluation of children with obesity. Future research should explore the mechanisms underlying this relationship, evaluating targeted exercise programs as potential strategies for MetS prevention in children with obesity.