I've had people question my eating choices pretty much my whole adult life. It's not that I eat any special diet, it's just that I eat healthily! No junk food, no fast food, no donuts. In New England, if you don't eat donuts, it's like a sin. Really, I eat a balanced, healthy diet, including meat and wine. The only thing I've cut down on is carbs, as I get older.
I even had people question my friends to see if I was anorexic when I was in my 30s and very thin just from exercising. One friend in AZ just about laughed the questioner off by saying I went out to Swensens to eat ice cream with her, at least once a week, which was true.
People also question me about my exercise habits, too. They think I'm crazy and they keep complaining about their bodies.