athletic is achieved at 9 fitness points. you start with 5 points, put the athletic trait adds 4 fitness points, but if you put underweight it takes -1 fitness point reducing you to 8 points and you will only have Fit which is given above 6 fitness points. increase fitness at 9 point with gymnastics and you will have athletic trait again. these are traits that can be changed, like underweight if you eat a lot and get to 75 in weight you will eventually lose that negative trait