I've got to disagree with Dave here, with all respect. Eating is about pleasure. If we concerned ourselves only with being healthy, to quote Colonel Trautman from the Rambo movies, we'd be eating things that would make a billy goat puke. This is the problem in the US, if you ask me - we're so worried about nutrition that we forget that eating is more than nutrients. It is culture, shared experiences, memories. I'd rather eat good food properly prepared with care and with people I care about than count every carb, fat, and protein. I mean, what's the point of eating if one is fretting over every gram of fat, carb, etc.? It takes all the joy out of it if you ask me.
This being said, sure there are some folks who's health problems dictate they must eat certain foods, and not others. And that's cool. Others make a choice not to eat certain foods, and that's fine as well.
What bugs me as a cook and aspiring chef is that some of these folks on the fringes would deny us those things we take pleasure in as omnivores or carnivores. Don't believe me? Last year, Chicago banned foie gras (livers from specially fattened ducks). Apparently, someone in their city council objected to the way the ducks are raised (they are force fed grain with a tube), and hence the ban. It was reversed in 2008, but you can see my point. Who are they to tell me and others who enjoy foie gras what we can eat and what we can't? I mean, what's next? Peanut butter?
Vegans and vegetarians, due to their choice, by nature have to pay more attention to their diets and nutrition mainly because a lot of the nutrients they need are abundant in animal products and less so in vegetable products. Meats are full of proteins, while vegetables (with the exception of quinoa) are not for the most part. The body needs protein, as well as carbohydrates and fat, and most veggies are high in carbohydrates, have some fats, but are generally low in protein. As a result, vegans and vegetarians must pay more attention to their diet - if they didn't there would be serious health risks.
I live above a vegan/vegetarian restaurant here in Montpelier VT where I'm attending culinary school. I ate there once. Much of what they had was very bland tasting to me. It may have had something to do with the seasoning, but I expected more - when one takes animal fats out of the diet, meat, etc., they must be replaced with something that is visually appealing, tastes good, and has good texture. None of what I ate had that, although I admit it wasn't the worst thing I've ever eaten.
BTW, I don't eat at McDonald's, Burger King, KFC, Pizza Hut or any of the other fast food places either. It's garbage IMHO. If others want to eat there, great. I wouldn't go out of my way to ban them like some of the PETA folks did with foie gras in Chicago.
In the end, as a cook and aspiring chef, I have no choice but to accomodate their wishes even though I don't necessarily agree with their choices (tempeh is the nastiest thing I've ever eaten, and I've eaten fresh, still squirming squid tentacles in Korea). Besides, grilled veggies suits my food cost just fine.
Alan