I'm an opportunistic omnivore and eat whatever is cheap and locally grown when I can. If I have tomatoes ripe, I eat tomatoes. If I have bananas ripe, I eat bananas, caught fish I eat fish, shot Bambi, I eat venison, made cheese, I eat cheese etc..
You have to be careful with vegetarianism and especially veganism, as there are some nutrients that are difficult to get and there are some right nutters promoting these diets who haven't done their homework. or aren't suffering the known deficiencies yet, or worse, are having symptoms but are ignoring them thinking that they haven't been following their chosen diet Guru as strictly as they should have.been.
The important lesson I learned when playing with restrictive diets, was that failure to thrive on a chosen diet is likely to be more about the poor nutrition from the food choices than from your ability to stick to the rules and that trying harder to obey the rules may make your chance of thriving worse.