Does Body Fat Mass Influence the Timing of Puberty in Boys with Constitutional Delay of Growth and Puberty?

OBJECTIVE: In girls, a strong relationship exists between body fat percentage (BFP) and pubertal development, with a critical fat threshold considered essential for the initiation of puberty. In contrast, research addressing the impact of body composition on the timing of puberty in boys remains limited, and the available findings are inconsistent. To evaluate the association between body composition and delayed pubertal development in boys with constitutional delay of growth and puberty (CDGP) compared with healthy peers. METHODS: Thirty-one boys with CDGP and 31 age-matched healthy males (Tanner stage 2-4) were included. Body composition was assessed using bioelectrical impedance analysis. Body fat percentage (BFP), fat mass (FM), fat-free mass (FFM), fat mass index (FMI), and fat-free mass index (FFMI) were evaluated. A BFP value of 17% was used as a descriptive reference rather than a validated biological cut-off. RESULTS: The mean chronological age was 14.1 ± 0.5 years in the CDGP group and 13.9 ± 1.1 years in the control group (P = .4). Compared with controls, boys with CDGP had significantly lower body mass index (BMI) standard deviation (SD) scores (P = .01). FM and FM SD scores were also significantly lower (both P = .002), and BFP was reduced (P = .03). No significant difference in BFP SD score was observed between groups (P > .05). The FFM/FM ratio was higher in the CDGP group (P = .04). FMI, FMI SD score, FFMI, and FFMI SD score were all significantly lower in boys with CDGP (P = .02, P = .02, P = .009, and P = .009, respectively). A BFP below 17% was observed in 58.1% of CDGP patients compared with 9.7% of controls (P < .001). CONCLUSION: Lower BMI, FM, and FFMI were associated with delayed pubertal onset in boys with CDGP, suggesting a potential relationship between reduced adiposity, lean mass, and the timing of pubertal development.