Offering healthier foods at school isn't enough to take on the childhood obesity epidemic according to a new study at the University of Oregon. That's because kids acquire their tastes much earlier. Experts say it’s evident because in cafeterias, the pizza bar is emptied much soon her than the salad bar, and that’s because those tastes were learned earlier in life.   Bettina Cornwell says their study found many preschoolers prefer salt sugar and fat because that's what they're exposed to by their parents and TV advertising.