This interventional single-center prospective open-label study aims to evaluate the effects of a vegan diet, compared to a vegetarian and omnivorous diet, on metabolic parameters, insulin sensitivity, and liver and kidney steatosis in healthy adults. The study included 53 omnivorous participants aged 18-40 years, body-mass index 18-30 kg/m2, without any chronic disease, chronic medication use, active smoking, or significant alcohol consumption. All participants were omnivorous at baseline and selected to continue an omnivorous diet or transition to a vegetarian or vegan diet, with follow-up over six months. Anthropometric measurements, biochemical parameters, and liver and kidney steatosis were assessed at baseline and after six months using magnetic resonance imaging-proton density fat fraction (MRI-PDFF). Primary outcomes included changes in liver and kidney steatosis, while secondary outcomes were alterations in anthropometric and biochemical markers. Among 53 participants, 18 followed an omnivorous diet, 21 adopted a vegetarian diet, and 14 transitioned to a vegan diet. Dietary interventions did not result in statistically significant changes in body mass index, fat mass, fat percentage, or muscle mass over six months. However, statistically significant improvements in systolic and diastolic blood pressure, favoring the vegan diet, were observed. We aimed to control for potentially confounding variables to ensure the reliability of these findings. We have demonstrated a better decline in steatosis at the lower kidney pole, the total hilus and the Liver 6 index in vegans. We demonstrated that a plant-based diet is associated with improvements in several metabolic parameters and may reduce liver and kidney steatosis.