Knowledge on the characteristics of consumers who choose plant-based diets and the relationship with nutritional status and disease risk is needed. In the present study, 207 Spanish adults participated in a cross-sectional study, and were classified in three groups: lacto-ovo vegetarian (LOV), vegan (VEG), and omnivore (OMN). Dietary intake, anthropometry, body composition, haematology, and metabolic markers were evaluated. Body composition and body weight did not vary among groups. The majority of these adults performed moderate-vigorous physical activity, and LOV performed more moderate activity than OMN. Total energy intake (En) was similar in the three groups. However, cholesterol and fat intakes (%En) were higher in the order OMN, LOV, VEG, fibre and carbohydrate intakes showed the opposite trend, and protein intake (%En) was higher in OMN than both LOV and VEG (all p < 0.001). Systolic blood pressure (p = 0.04), erythrocytes (p < 0.001), and haematocrit (p < 0.001) were lower in LOV and VEG than OMN, and lymphocyte count was lower in LOV than OMN (p < 0.01). There were marked differences between groups in serum total-cholesterol and LDL-cholesterol that were lower in LOV and VEG than OMN (both p < 0.001). However, glucose, insulin and insulin resistance did not show group differences. Leptin and adiponectin were related with gender and body fat but not with diet. The inflammation marker interleukin-1β was lower in LOV than OMN but TNF-α did not show differences. All levels were within normal ranges. Conclusion: consumption of plant-based diets compared to omnivorous diets in combination with moderate-high physical activity appears to protect similarly from cardiometabolic diseases in Spanish adults.