Varian says "I don't think I know anyone who absolutely never eats vegetables, cereals or fruit - that would be a pretty unhealthy diet." (Can't get the ^to work and make italics)
Actually, I did have a colleague who was diagnosed as fructose intolerant. Fortunately, he had had a small office to himself, but even then, through the walls, we could hear his (to put it delicately) digestive problems. After the diagnosis, he had to eat some weird stuff, but it did the trick.
He had to avoid all fruit and veg, most grains - no sugar, of course, in any form. The only vegetable he could eat seemed to be rice. He was very open about it and there were many interesting conversations in the kitchen, especially as he lived alone, but had never done much cooking or baking before.
There were a couple of vegans and vegetarians in the office too, but I can't say that anyone was ever offensive to any of them about it.
Among my colleagues and acquaintances, once it has been established that someone is vegan or vegetarian, the subject hardly comes up again, except on birthdays, when the birthday person usually tried to provide a vegetarian alternative, or some fruit or something. (It is traditional here in Germany for the birthday girl/boy to bring cakes on their birthday, but a cheeseboard is also not unusual).