Why Slim in 6 Works: Slim Training Slim in 6 is more effective at helping you lose weight than those super-intense, high-impact workouts. The secret is Debbie's Slim Training, a combination of low-impact cardio moves and light resistance that gets you into the optimal fat-burning zone—and keeps you there longer. The fat melts away as you tone lean muscle, so you get incredible body-shaping results, faster!