Background <p>The growing need for a sustainable and personalised diet requires new tools to evaluate plant-based dietary orientation.</p> Methods <p>We developed a composite dietary score combining food preferences and weekly consumption frequency to quantify plant- and animal-based dietary patterns. In a cross-sectional sample, we assessed associations between these scores and body composition outcomes, including BMI and fat mass percentage.</p> Results <p>The plant-based diet score was inversely associated with BMI (β = − 0.28, <i>p</i> = 0.0032) and percentage fat mass (β = − 0.81, <i>p</i> &lt; 0.0001), independent of age and gender. The animal-based score showed no significant association with BMI (β = + 0.19, <i>p</i> = 0.057) or percentage fat mass (β = + 0.13, <i>p</i> = 0.36). In contrast, the plant–animal differential score was inversely associated with BMI (β = − 0.24, <i>p</i> = 0.0008) and percentage fat mass (β = − 0.31, <i>p</i> = 0.0021). This association was more pronounced among individuals with BMI ≥ 25&#xa0;kg/m² (interaction <i>p</i> = 0.0418). Clustering analysis based on plant and animal scores identified three distinct dietary profiles—high-plant/low-animal, mixed, and low-plant/moderate-animal—which differed significantly in BMI (<i>p</i> = 0.0009) and fat mass (<i>p</i> &lt; 0.0001).</p> Conclusions <p>Plant-based dietary orientation, as detected by our scoring method, is strongly associated with favourable body composition. These results support the utility of integrative dietary scoring systems in the assessment of sustainable dietary behaviours with metabolic relevance.</p>