(13-10-11) Why You Have to Feed Your Brain

by Victor Marchione, MD

Forget the stomach for a second: don't let your brain go hungry. This is a key thing to consider for anyone looking to shed pounds or eat healthier. In a new study amid the swirling pool of health tips for nutrition, researchers have found that, if your brain is hungry, the impulse to eat junk food grows larger.

Brain imaging scans show that, when glucose levels drop, an area of the brain known to regulate emotions and impulses loses the ability to dampen desire for high-calorie food. Quite simply, your prefrontal cortex just loves sugar. If it's kept satiated, it won't want to seek a sweet snack.

The study researchers manipulated glucose levels intravenously and monitored changes in blood sugar levels while people were shown pictures of high-calorie food, low-calorie food, and non-food. MRI scans were used to see what happened in the brain.

When glucose levels drop, an area of the brain called the "hypothalamus" senses the change. Other regions associated with reward are activated, inducing a desire to eat, the study found. The most pronounced reaction to reduced glucose levels was seen in the prefrontal cortex. When glucose is lowered, the prefrontal cortex seemed to lose its ability to stop increasingly urgent signals to eat. This weakened response was particularly striking in the obese when shown high-calorie foods.

Obese individuals may have a limited ability to inhibit the impulsive drive to eat. That becomes overbearingly so if glucose levels drop. Another area of the brain, the striatum, became hyperactive when glucose levels dropped. But the stress hormone cortisol played a bigger role than glucose in activating the brain's reward centers. Thus, if you are stressed out and your blood sugar drops, you face a huge desire to eat junk food.

The key amid all this is clear: eat healthful foods that keep your blood sugar levels in check. Fruit is an excellent idea, as it contains much natural sugar, but is still dense in nutrients. Just remember, if you are trying to shed pounds, your brain needs its food. If you think fighting your waistline is hard, try fighting your brain.

Source: Page, K., et al., "Circulating glucose levels modulate neural control of desire for high-calorie foods in humans," The Journal of Clinical Investigation, published online Sept. 19, 2011.

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