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Or at least stop obsessing about not doing them. "Spot training is never the key to a flat belly," says Gregory Joujon-Roche of L.A.'s Holistic Fitness. Joujon-Roche, who has worked with Demi Moore, says cardio exercise like jumping rope or interval training is just as important. Start with 20 minutes three times a week, and work hard enough to break a sweat.