I don't know whether this is just me or commonplace.
I think that I eat a fairly normal diet. I eat junk food and crap but I eat healthily too. I'm a completely normal weight and I don't diet or ask anyone's opinions on food.
There's a few people mainly at work who seem to constantly comment on what I'm eating.
If I bring lots of fruit and a salad I get "ooo you're being healthy aren't you". I don't mind this one so much. But if I bring a ready meal (rare), or go and buy a sandwich from subway (again rare), I get comments like "you're not going to eat that are you", or them telling me it's rubbish or full of chemicals.
They might ask what I did at the weekend and I might say. I went to McDonalds and the cinema, and I get comments about how McDonalds is vile and full of air. The worst though is when I'm eating something or drinking a can of coke and people actually pull faces of disgust while I'm eating.
The fact is that I don't really care, if I'm eating a ready meal or drinking a can of coke the chances are I was too late to prepare my lunch or I'm on my period and craving crap. 90% of the time I have water, fruit and a homemade sandwich or leftover stew or something. But I've nothing against convenience food or takeaways in moderation.
The best of it is though, the people who comment are the worst culprits, and eat rubbish themselves most days but seem to think that their crisps, Fanta and micro rice are superior to my food.