These chemicals send signals to the stomach, directing it to hunger for nutrients that the body theoretically needs. The result, now close at hand, is a group of experimental drugs that disrupt the cycle and sharply reduce the cravings. There is some biochemical logic to our dietary habits. Another brain chemical, serotonin, turns off NPY production, and around lunchtime triggers a demand for protein. At about the same time another chemical, galanin, starts to kick in, causing us to crave fat.
Hormones can also affect food cravings.
Science is determined not just to understand galanin, but to gain the upper hand so that one day we can turn down our fat cravings. One scientist has developed an experimental drug called M40 that acts as a galanin blocker. Another researcher has found that injecting a protein called enterostatin into animals causes them to cut their fat intake. Eating a high-fat diet may stimulate the desire for even more fat. But if you don't respond to your physiological signals, there's a rebound effect, and the signals will hit you harder.