Being a low-carber since 2009 and running my website on this dietary approach, I can tell you many a vegetarian/vegan have posted on my LC forums they now know they have done irreparable damage to their health/bodies for having followed those lifestyles for many years. Their doctors tell them they can do little to reverse that damage. Meat provides some nutrients, minerals etc. other foods just do not in adequate amounts. I don't personally know, as I've never been vegetarian, but my sister-in-law is. I have shared with her what others have said regarding their regrets on the subject. I did notice that when Bill Clinton went vegan, he started looking like death warmed over. Of course, in Bill's case, that could be due to a variety of other past times. LOL