If you're going to commit to a diet for the long term, it had better include desserts. "When people try to give things up, they often rebound-overeat," says Cynthia Sass, R.D., a coauthor of Your Diet Is Driving Me Crazy (Marlowe & Company, $15, www.amazon.com). The key is moderation, which means either splurging once in a while (cheesecake or a hot-fudge sundae once a week) or having more frequent treats that are smaller or less indulgent. Sass suggests a piece of quality chocolate every day or a few cookies a few times a week. Suzanne Farrell, R.D., a spokesperson for the American Dietetic Association, encourages her clients to try what she calls "plan B" sweets for when the urge hits: fat-free pudding, a low-calorie Fudgsicle, or a mini parfait of berries, low-fat yogurt, and some crushed graham crackers.