The Association Between Measures of Fitness and Metabolic Health in Treatment-Seeking Youth with Obesity

Background: Both cardiorespiratory fitness (CRF) and measures of muscular fitness are associated with metabolic syndrome in adults. However, limited information exists about these relationships in youth with severe obesity who are at increased risk of metabolic dysfunction. The purpose of this study was to examine the relationship between fitness and metabolic health in treatment-seeking youth with obesity. Methods: Data for this analysis were collected at the time of baseline visits at a stage 3 pediatric weight management center. Maximal voluntary contractions were obtained by using isometric hand-grip dynamometry, and CRF was obtained from a maximal treadmill test. Resting blood pressure and fasting measures of blood lipids, glucose, and insulin were used to calculate a continuous metabolic syndrome score (cMetS); homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from fasting insulin and glucose. Relationships between measures of fitness and metabolic health were evaluated by using partial correlations adjusted for age. Results: Sixty-nine participants (21 boys, 48 girls) were included in this analysis. Of these, 46% (n = 32) met the criteria for metabolic syndrome. No differences were found between boys and girls for any variable analyzed. Muscular strength was positively associated with cMetS (r = 0.35), though this association weakened after adjustment for body mass index percentile. CRF was inversely associated with homeostasis model assessment of insulin resistance (HOMA-IR) (r=-0.26) and fasting insulin (r=-0.27). Body fat percentage was positively associated with insulin (r = 0.36). No significant relationship was found between CRF and cMetS. Conclusion: Contrary to previous studies, CRF was not associated with metabolic syndrome in this group. Muscular strength, however, was associated with cMetS. Notably, CRF was associated with elevated HOMA-IR, which may be seen as a precursor to metabolic syndrome. These results suggest that CRF and muscular strength influence metabolic function independently.