Obstacle: We are programmed to love fat. It was the best possible fuel for Stone Age humans—calorie-dense, easily stored, long-lasting.

Strategy: The less fat you eat, the less fat you'll want. Try skim and low-fat dairy products, and when baking, substitute fruit purees for fats and evaporated skim milk for heavy cream in recipes. It takes a few weeks, but you really can retrain your tastes to prefer the lighter versions. A follow-up study of participants in the Women's Health Trial found that those eating a diet of only 20 percent fat developed aversions to the high-fat foods they used to prefer.

Obstacle: We have an innate preference for familiar foods—a safeguard left over from prehistoric times, when unfamiliar foods could turn out to be poisonous. This is why we find the dishes our mothers fed to us as children comforting. Unfortunately, these foods—macaroni and chees, cookies and milk—are good for the sould but bad for the waistline.

Strategy: Katz insists you can get used to any new taste if you move slowly. Experiment with fruits and vegetables you haven't tried and with different ways of preparing those you have; use familiar spices and condiments for a link to you favorite tastes. And remember that you—not the vending machine—are the boss.

Next: Get Dr. Katz's Top 10 Rules for Eating Right