I don't see how being vegan alone can end world hunger. Many countries live in very dry land. Veggies and fruits spoil within a short period of time (meat does too, but it's easier to freeze/season etc to last longer). The amount of fuel it would take to continuously fly back and forth would be insane. Fuel prices are constantly rising, because apparently the earth is running out. Using the fuel to transport veggies back and forth could only stop world hunger for a very limited time (assuming your theory is true.)
2. Animals eat plants when people eat meat and plants. Animals also eat plants when people eat meat only. Eating plants + meat would have very little effect than just eating plants (even if people were fattening the animals.) Where there are vegetarians, there are also meatatarians.
3. That soy, organic, and produce in general is really expensive. I'm trying to pay for school, my rent/bills, a child, and feed my family and often lose money as it is. Buying a gallon of milk that came from a cow and a dozen eggs that came from an egg prevents MY WORLD HUNGER. The real hamburger and chicken stuff is cheaper, tastes better, and keeps me from starving.
Most of a person's main dietary need comes directly from starch in the form of rice/potato/etc. Eating animals products happens to be highly inefficient, because as you move up each level of biological hierarchy, only about 10% of the net energy gets transferred.
"MOST!" does not equal "ALL". 10%>0%. I agree with bolt. If I eat 1 serving of meat and 1 serving of veggies, I am even more full than say I eat like 6 servings of veggies. Animals see the need to eat other animals for energy rather than just plants. There is a lot of protein in meat, which is definitely beneficial to the human body. Most of the protein in the organic/soy sections of the stores are man-made, hence a reason they cost more.