Associations Between Vegetarian Diet and Bioelectrical Impedance Parameters: Insights into Body Composition and Cellular Health in Young Adult Women

Background: Vegetarian diets are becoming increasingly popular among young adults. The aim of this study was to examine the association between adherence to a vegetarian diet and body composition parameters in young adult women. Methods: A sample of 647 young adult women, mainly university students from Slovakia, consisting of 66 vegetarians (22.02 ± 2.74 years old) and 581 omnivores (21.13 ± 2.20 years old) was analysed. Body composition was measured using a bioelectrical impedance analyser, the InBody 770. Information on participants’ diet was collected using a modified version of the WHO STEPS 2014 questionnaire. Results: Vegetarian women showed significantly lower phase angle (PhA) values compared with omnivores (5.06 ± 0.45 vs. 5.23 ± 0.48; p = 0.004). They also had a higher extracellular-to-total body water ratio (ECW/TBW; 0.382 ± 0.004 vs. 0.380 ± 0.005; p = 0.026). In multivariable linear regression adjusted for smoking status, physical activity, body mass index (BMI) and waist-to-hip ratio (WHR), vegetarian diet remained independently associated with lower PhA (β = −0.094; p = 0.011) and higher ECW/TBW (β = 0.085; p = 0.028). No significant indirect associations between a vegetarian diet and PhA or ECW/TBW through smoking status or physical activity were observed. Conclusions: In this study of young adult Slovak women, adherence to a vegetarian diet was independently associated with lower PhA and a higher ECW/TBW ratio. These findings indicate differences in BIA-derived indicators of cellular integrity and fluid distribution between vegetarian and omnivorous women, although causal relationships cannot be inferred.