Health tip: MythBuster: IF YOU EXERCISE, YOU CAN EAT WHAT YOU WANT--While exercise does burn calories, what and how much you eat still matters—a lot," Kim says. "For example, a one-mile walk burns about 100 calories — so you’d have to walk for 12 miles to burn off the typical 1,200-calorie fast-food meal of a hamburger, fries, and a soft drink!"