I often leave work get the train for a 1hr 20min journey into London. I either plan before hand and take a sandwich to eat on the train or I pick something up from a shop & eat on the hoof on the way there if I'm unable to factor time for a sit down meal. If not I try to get something to eat prior to the train home. I usually arrive home at 0130 so could potentially have gone over 12 hours without food, this isnt a hardship if I get to see a show. Im not being a martyr here but showing that someone even with my capacity to eat can do it.
Regarding what people eat during an interval, it can be a problem if they are eating warm pasties and smelly sausages (you'd have to scroll back many tweets to see what I mean by that) as it makes me want to gag. If I was on a tube I could move away unfortunately being confined to a specific seat means moving isn't possible. I also think drinks (other than water) should not be allowed in the auditorium, the smell of cheap but overpriced wine is really something that should be confined to the bar. I actually just bloody wish people would stop treating the theatre as if they are sat at home on their sofa with their feet up, eating a takeaway and chatting to their family. If that's what you want from a night then stay at home, it's simple.
I actually find this attitude really annoying. So if you're not willing to go without food for 12 hours, not have a drink all night and sit in complete silence you shouldn't go to the theatre?
We wouldn't have a thriving theatre scene if everyone had to meet your standards - people really would stay at home! A night at the theatre is meant to be entertaining, not an endurance test.
I'm as annoyed by anyone else by genuinely disruptive behaviour, but really, if the smell (or sight - ice cream doesn't have a noticeable smell, it's the mere sight of people eating it that offended your sensibilities in your original post) of food and alcohol affects you *that* badly, maybe you should be the one who stays at home. That would certainly represent less of a financial loss to the theatre than everyone else staying away!