In my diploma, I wanted to shine a little light on a rather rare metabolic disease named PKU and give a picture of a life and struggles, a sportsman with such a disease has. This particular diploma also has a biographical note, since a lot of it is based on my personal life experiences.The main focus of the diploma is on a question, weather a person with PKU has any chance to succeed in sport. I tried to present and describe phenylketonuria and describe, how a life of a person with PKU looks like. Furthermore, I examined and compared two diet plans. One of a normal healthy sportsman and one from a PKU patient. The last chapter is a description of an experiment I have conducted on myself in the last two years. I wanted to find out how important good nutrition really is for a sportsman. Particularly, I was interested in the importance of proteins intake. The experiment was conducted in three sequent parts with as similar amount of training and physical activity as possible and different diet plans. In the last part, I've tried to get as close as I can, without endangering my wellbeing, to an optimal nutrition. To achieve that, I used a well-known food supplement, creatine monohydrate, which I can not get into my system with regular food. However, the results should be taken with some caution, since the experiment had several imperfections. Especially the fact, that it had been done on just one subject.