Fruits and veggies: bad or good?

my brother and i are having arguments about whats good and bad....he's decided that he was just going to cut out almost everything from his diet and i think he's being absolutley ridiculas. he won't eat melons or carrots or avacodo....basicly anything that has sugar in it. he won't eat meat because he says its all bad. he takes stacker 2 and alli. he doesn't eat anything with sugar, nothing thats more the 5 grams fat. theres more but i think he is just not getting enough vitamins. he's lost 50-60 pounds in 2 months and he's still going. which i'm happy for him but i was told 2 pounds a week. oh and he was not having bowel movements for 2 days. weird! someone give me advice on whats right and wrong?