Rock Doc

Lots of us have observed that foods that are good for us - broccoli and bean sprouts - don't trigger intense cravings. In the late afternoon, when my energy is low, I want a cookie or a piece of chocolate, not a green pepper. Similarly, when I walk around the grocery store, I go through the meats and produce section without feeling deep cravings for the food I see. But when I get to the bakery, all bets are off, even if I'm not hungry.

These patterns of cravings are significant because what we eat affects our health so much. Obesity and diabetes are more and more problematic in the U.S., and a...