The Neurology of Eating

Any attempt at weight management that fails to address the whole person is doomed to failure.

It is not enough to diet and exercise, and whatever the truth of manifesting, you cannot think yourself thin. Success demands an approach that integrates every system of your body, mind, social and subtle systems. For many people there is even an important role for integrating their spirituality into a plan for healthy living.

So we need to learn as much as we can about each component. Some fascinating new research has added some important pieces to the puzzle.

Writing in the journal Nature a group of scientists from University College London and King’s College London used peptide YY (PYY), a naturally occurring hormone that regulates appetite, to investigate which areas of the brain are involved in controlling food intake.

PYY is released into the bloodstream from the intestine after we eat something. In animals PYY signals the appetite control centers in the hypothalamus and brainstem that food has been eaten. Injections of this hormone have been shown to decrease food intake both in healthy volunteers and in people with obesity.

The hypothalamus and brainstem are ancient regions of the brain involved I te most basic functions. But humans have complex, highly developed brains, and the question was to discover how PYY regulates eating in humans.

The study involved eight normal weight men in a double blind placebo-controlled study. After 14 hours without food the subjects were given an intravenous infusion of either PYY or placebo for 100 minutes. During all this their brains were scanned continuously using functional Magnetic Resonance Imaging (fMRI). Thirty minutes later they were offered an unlimited meal. Each subject was tested twice one week apart, once with PYY and once with the placebo. PYY infusion reduced food consumption in all 8 subjects and on average caused a 25% reduction in the calories eaten.

Now it gets interesting. The fMRI scans showed that PYY not only targets the primitive parts of our brain that control feeding but it also acts in the corticolimbic brain regions that are involved in the rewarding and pleasurable aspects of eating.

The greatest change in brain activity in response to PYY was within the orbitofrontal cortex (OFC), a region that acts as an integrative center in the brain and is also implicated in reward processing. The change in OFC activity predicted how much food the volunteers subsequently ate. The greater the activation, the less people.

When we are hungry, brain activity within the hypothalamus predicts how much food we should eat. However an infusion of PYY tricks the brain into thinking that it has eaten, and switches on the circuits that control eating. The activity in the orbitofrontal cortex now predicts how much people will eat in the future.

If you have not eaten for a long time, you get full very quickly. It is not that your stomach has shrunk; it is that the production of hormones like PYY has been turned down. When you eat, they are over-produced and switch off more eating. When someone has gastric bypass surgery, their levels of PYY go up and stay up.

An important aspect of weight management is to retrain and reprogram the mind and body.

This research helps to show us how the approach works.