Your grandpa was a svelte boss. You, by comparison, are a junk-gobbling slob, according to a slick new split-screen ad for Coca-Cola from agency David in Buenos Aires. The spot, part of a larger effort to position Coke as anti-obesity, is meant to compare granddad's modest approach to life with today's steady diet of too much everything: oversized sandwiches, lattes and pre-TV-dinner hot dogs. Don't cut out Coca-Cola, though. Sugar water is cool, so long as you're riding your bike to work and taking the stairs.