Muscle-to-Fat Ratio for Predicting Metabolic Syndrome Components in Children with Overweight and Obesity.

Background: Pediatric obesity has been linked to the components of metabolic syndrome (MetS: abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, and insulin resistance). Data on the role of muscle mass in the development of MetS are sparse. We explored the interaction between the muscle-to-fat ratio (MFR) and MetS components in children with overweight or obesity. Methods: An observational study of 210 pediatric subjects (88 boys, mean age [±standard deviation (SD)] 11.9 ± 3.1 years, BMI z-score range 1.036-3.140) from January 2018 to January 2021. Body composition was measured by bioelectrical impedance analysis (Tanita MC-780 MA and GMON Professional Software), and MFR z-scores were calculated. Results: The 148 subjects (70%) who had MetS components were older (p = 0.008), had lower socioeconomic positions, higher triglyceride/high-density lipoprotein-cholesterol ratios, fat percentages (FATP), truncal FATPs (TRFATPs), and lower MFR z-scores (p < 0.001 for all parameters) than those without MetS components. The correlation between the MFR z-score and the BMI z-score was stronger in subjects with obesity than in subjects with overweight (r = -0.556 vs. r = -0.440, p < 0.001 for both). The risk for MetS components increased by 1.4 for every 3% increase in FATP or TRFATP [odds ratio (OR) = 1.4, confidence interval ([CI] 1.20, 1.64), p < 0.001]. The risk for MetS components was tripled for every 1 SD decrease in MFR z-scores [OR = 3.3, CI (1.74, 6.27), p < 0.001]. Conclusions: Given the strong predictive value of the MFR z-score in the development of early-onset MetS components, preventive strategies should apply interventions for improving the body composition parameters of both adiposity and muscle.