I used to be 50 pounds overweight and rarely got negative comments. Now that I've gotten my BMI down to a normal and healthy 20-21.5 range, I get skinny-shamed all the time. At first it bothered me, because I was feeling positive about the success in getting healthy, and the feedback was negative.
I've since learned not to take it personally, because it comes from insecurities people have about themselves. They're jealous. There's no reason to let others' insecurities spoil your enjoyment of running, racing, looking and feeling healthy.