. >> reporter: eric schlosser spent two years researching the fast food industry. he wrote a book just for kids called "chew on this -- everything you don't want to know about fast food." it includes one surprising fact about those mcdonald's french fries many of us love. >> they're salty, and mcdonald's puts a little extra something in them. and when i was doing research for the book, i discovered that little extra thing is beef flavor. so the fries have beef in them, and if you're a vegetarian, you shouldn't eat them. >> reporter: eric isn't a vegetarian. in fact, like most of us, he loves a good burger. but he stopped eating fast food after he did his research. he already knew most fast food is not made fresh. it's processed -- created in a big factory, frozen, packaged and shipped around the world. that's why the food tastes the same no matter if you buy it in china or california. but eric was shocked to find out the taste and smell of fast food is not natural. >> this fast food is so heavily processed that while they're processing it, it loses its flavor. so t