If we had to live off of only vegetation, including fruit, we would eat a lot more food. IOW, a VERY large salad with a variety of lettuce and veggies, a cup of sunflower seeds, two apples, two oranges, 1-2 slices of whole wheat bread with an olive oil spread, and a cup of rice milk(to wash it all down) as a meal is sufficient for our health as humans. Not consuming meat makes us eat more food, the kind of food that's better for our health.
I disagree with the fruit only diet because consuming only fruit would leave us lacking many vital vitamins and nutrients. Yes fruit has an important place in our diet, but it shouldn't be the only thing we consume. For instance, we need calcium, which fruit doesn't provide. We have to get it from another source. Dairy should not be consumed, so I personally drink rice, almond, or oat milk.