Not a runner? No sweat. Start a walking routine instead. Researchers found that overweight women who did 45-minute speed-interval walking workouts and toning exercises four times a week lost 23 pounds in 16 weeks. The key is to perfect your form, so that walking feels good and doesnt become boring over time, says Danny Dreyer, the creator of the Chi Walking technique. Fast-track your fat burning while you walk with these easy tweaks.