The main purpose of this research is to find out, how well do men, who work out in a gym, know the dietary supplements, how much do they use them and whether or not the dietary supplements affect their body structure in a positive way or not. 50 men from the age of 18 to 60, who work out on a regular basis (at least two times a week), were included in this research, which took place from March to July 2016 in six different gyms across Ljubljana. The research includes the measurements of the body structure that were completed with Tanita scale (Tanita, Innerscan body composition monitor, model BC-545), which is based on six point measurement with magnetic impedance. It is also based on survey questionnaire that includes questions about age, gender, children, education, the way and quantity of a workout, knowledge and usage of dietary supplements.
We found out that 84% of men, who work out on a regular basis, use dietary supplements. We also found out that men, who use dietary supplements, have a higher height, lower percentage of fat and muscle mass. The research also showed that 54% of men, who workout in a gym, have poor knowledge about dietary supplements. The comparison between two age groups (under 40 years and above 40 years) showed that older people have higher percentage of body fat and higher vital age.