Background <p>Omentin-1 (also known as intelectin-1) is a novel adipokine associated with metabolic diseases. However, its physiological role in body composition remains incompletely understood. Therefore, this study aimed to investigate the association between the circulating omentin-1 levels and whole-body and regional body composition parameters measured using dual-energy X-ray absorptiometry (DXA).</p> Methods <p>A population-based cross-sectional survey was conducted among school-aged children in Hamamatsu, Japan. Serum adipokine levels were measured using enzyme-linked immunosorbent assay, and associations between omentin-1 levels and DXA-based parameters were evaluated by multiple regression analysis after adjusting for potential confounding factors.</p> Results <p>The final study included 392 participants (192 boys, 200 girls, 75.2% of the source population; mean age 11.2 ± 0.3&#xa0;years). Serum omentin-1 levels showed a significantly inverse association with nearly all DXA-based fat mass parameters. Inverse correlations were observed with fat-free soft tissue mass and serum leptin levels, whereas positive correlations were noted with adiponectin levels. The mean values for various body fat parameters, fat-free soft tissue mass, body mass index, and waist circumference were significantly decreased across tertiles of serum omentin-1 levels from lowest to the highest after adjusting for potential confounders.</p> Conclusion <p>Our results demonstrate that Japanese school-aged children with higher fat mass tended to have lower serum omentin-1 levels. These findings provide crucial insights into the link between omentin-1 levels and body composition, which may contribute to early health interventions for metabolic improvement.</p>