Just try to ignore comments like that and maybe consider taking a look at who you are spending your time around. Personally, I got rid of the one person who made a smartassed comment to me and have barely said a word to him since. I realized that he's an arrogant, rude person and I feel better off without him.
Before I decided I wanted to be fit and not just thin, I settled for walking rather than jogging or running. But one night, partway into my walk, I thought, "I'm sick of this...I want off the treadmill...when can I stop?" I had to pick a point that I could stop at - a time or a distance? I went for the mile and it took me over 16 minutes to finish it. I had already been walking for like 10 so that's not a surprise.
When my "friend" asked me how long it took, he said, "Ouch, I could have done it in 10 and I don't even run much". I called him on it, said to show me, and he came up with some excuse for why he wasn't able to. Bull! This guy is a total chub, he couldn't do it in 10 if he was being chased!
After that, as he sat eating his sub and greasy chips, he teased me for eating "rabbit food". This was after he was also kind of a jerk with the cashier when we checked out and every rude, arrogant, or mean comment he'd ever made came rushing back and I realized......
........I really hate this guy.