Well I can assure you that for an entire week my DS1 ate absolutely nothing at all, drank no milk, had no soups, and had about 2 or 3oz of very diluted fruit juice a day.
He wouldn't touch anything else. I didn't make an issue of it, just offered him food and if he refused it (which he did) carried on with what I was doing.
We gave up and went back to giving him what he would eat and just offering other food as an option. I'm sure he would have gone on much longer if I'd let him, but I wasn't prepared to find out. Not when he was hardly touching liquids either.
He grew out of it totally within a couple of years and the only thing I can think of that he doesn't like (off the top of my head) is tomato ketchup.
DS2 will eat (and always has) eat anything except red onions and spinach. And DS3 hasn't as yet gone through a fussy stage. Although he's not a huge eater (despite his enormous size ) he doesn't like lentils or potatoes unless it's roast potatoes or home made wedges.
I went through a fussy stage when I Was about 10. I spent an entire summer eating nothing but cheese salads (and they were those "non" salad that consisted of throwing a few random bits of cucumber, lettuce, tomatoes on a plate and labelling it "salad") and the entire winter eating mince beef and onion pies .
"I agree that adults do have preferences, a friend that hates fish, one that's always dieting, another that's a vegetarian.... all get catered for here!"
You can be my friend (although I'm pretty easy to feed - just no olives or offal of any description please)