Is there anything “unhealthy” about eating Fruits and Vegetables?
No actually it is quite healthy. Your friend is obviously eating some protein source, either beans or tofu or nuts or he would deteriorate and die pretty quick. A well balanced vegetarian diet is actually far far better than a diet including meat. The only time a person would get sick off of it would be if they didn’t keep it balanced. There are probably at least a billion people on planet earth who don’t eat meat. In India where there are a lot of Hindus, and in much of Asia where Buddhism is commonly practiced, there are millions and millions who do not participate in meat eating ever in their lives and live much more healthily than the average meat eater.