In these master thesis we deal with vegan and omnivores of male and female gender, from the same age group (19-30 years), that are devote to moderate intense physical activity at least 150 minutes or very intense physical activity at least 75 minutes per week. We verified their body composition using bioelectrical impedance analysis, and the intake of macronutrients according to the recommended values.The essential difference between foods of animal origin and plant origin is primarily in their proteins, especially in bioavailability. Because omnivores have different source of protein intake, they should have a higher proportion of lean body mass. Physical activity is also important because it has a big impact on health and general well - being and also affects body composition. Bioelectrical impedance analysis (BIA) has been increasingly used to determine the composition of the body. BIA is a clinical method for assessing the body weight and fat percentage. Biomedical instruments measure resistance and reactance through body electrodes. In addition to the BIA, subjects also comleted online survey with a non-quantitative questionnaire on the predisposition to the use of individual food groups, and completing a nutritional diary on the consumption of foods in two non-consecutive days. Informations from diary were processed using online tool Open Clinical Nutrition Platform (OPKP).We found out that vegan diet did not affect the lower fat content in the body, we also did not confirm that the omnivores have a higher proportion of lean body mass than vegans. The diet can affect health indicators with a lifestyle that includes diet and the amount of physical activity.