Dude. That is not real food. It is in no way better for you than the meat versions. It is simply another version of bad.
If you wanna eat burgers, eat burgers. If you are genuinely concerned about diet, don't eat any of that fast food garbage.
Being vegetarian for health reasons then going to burger king is very oxymoronic. And if you have a philosophical problem with meat, then you shouldn't even step foot in a joint like BK.