Look Great in 08

DAY FOUR: EAT MINI MEALS

Eating small meals throughout the day boosts metabolism and prevents binge eating. "Every time you eat, your body burns calories," says Pachella. "So eating every two hours or so keeps your body working – and burning." Katherine Heigl's just one of the stars who has signed up for trainer Harley Pasternak's daily 5-Factor Diet, which includes five high-protein meals along with an exercise plan. "[Now] I wake up and I go, 'My God, I can't believe this is my body!' " Heigl told PEOPLE.