I'll be 17 at the end of the year, and I've decided I want to lose weight. I'm not really fat or anything, and I have a good amount of muscle, but can't get rid of the fat I have left. I've thought about taking up boxing because it looks fun and my friends who box love it, but I don't really want to fight anyone because I don't want to use violence unless it's in self defense. Are there any alternatives?