Beyond somatotype categories: composition-based clustering of body types in young adults

Somatotype analysis classifies individuals into 13 categories based on unique combinations of the three principal components: endomorphy, mesomorphy, and ectomorphy. This study aimed to examine sex-related differences and intra-category variability within somatotype classifications, and to characterize body composition patterns in the general population.

Anthropometric data were collected from 185 males and 156 females aged 18-40 years to estimate somatotype, fat mass index (FMI), and skeletal muscle index (SMI). Sex differences were evaluated with Hotelling's T² and chi-square tests, while within-category morphological dispersion was quantified as Euclidean distances from centroids. K-means clustering on FMI and SMI identified Low, Medium, and High groups, and somatotype distributions across clusters were compared using chi-square and binomial tests.

Men exhibited an Endomorphic-Mesomorph somatotype, whereas women displayed an Mesomorph-Endomorph profile. Hotelling's T² test confirmed significant sex differences in somatotype centroids (p < 0.001), and chi-square analyses showed strong associations between sex and somatotype categories (p < 0.001). Within-category morphological dispersion was significant in most groups, with males showing greater overall variability than females (p = 0.004). K-means clustering of FMI and SMI identified Low, Medium, and High groups, with somatotype distributions differing significantly across clusters (p < 0.001); a clear predominance of a single somatotype category was observed in the Medium FMI cluster of males (Endomorphic-Mesomorph, 76.8%, p < 0.001) and in the High SMI cluster of males (Endomorphic-Mesomorph, 67.5%, p = 0.019).

These findings highlight pronounced sex-related differences, considerable intra-category variability, and distinct body composition patterns across somatotypes in the general population. Notably, although individuals classified within the same somatotype can still present heterogeneous body shapes, the Endomorphic-Mesomorph profile distinctly characterizes males with moderate fat mass and higher muscle mass.