How to convince people im not a fat wimp?

i have lots of friends and im preety popular around my group.but some annyoying kids call me a wimp because i dont play contact sports. i swim and i like to run.but apparently thats not enough. And worse some of my friends are friends with the leader so im forced to hang with him. and he tries to insult as a joke.but it does hurt my feelings. And when someone else is buliled by this guy,i always defend them and i win but how come i cant do that when someone is bullyin gme :( please help sorry for the bad spelling im in a rush. and even my friends sometimes tell me im kinda wimpy although they say it nicer