I would not take it personally but take it as a challenge. I would start going the gym and eating more healthy. Then say in a few months when you see the person again, they will not be able to say, and the egg will be on their face!
That is an easy one for me. My ex use to call our daughter fat, and I divorced him. Period. I cannot stand people putting others down. It makes them feel better, but destroys our confidence. They need serious help. No one deserves to be called names. But, like I said I got away from the situation fast, and was the best decision ever. But ignore it. It is best not to fester back at someone like that, as they love a good fight. Good luck, and I am sorry if someone said that to you.
I would burst into tears as my fragile self esteem would be irreparably shattered, run straight home and contemplate suicide. Either that or I would completely blow them off. I'm too old to give a crap about what anyone says.