Your brain on food: Obesity, fasting and addiction

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(CNN) - We all know that what you eat can change your physical appearance. It also alters how your body functions, making it more or less difficult to pump blood, grow healthy bones or process insulin.

New research presented this week at the Neuroscience 2012 conference suggests that what you eat can even alter your brain -- and vice versa.

Timothy Verstynen and his colleagues used functional magnetic resonance imaging (fMRI) to observe the brain activity in 29 adults. The study participants were shown words on a screen in various colors and asked to identify the color, not the word. Sometimes it was easy -- the word red printed in red; other times it was harder, like seeing the word red printed in blue.

The overweight and obese participants' brains showed more activity during difficult questions, suggesting they were working harder to get the same answers.

Verstynen said the results imply that obese people are less efficient at making complex decisions, which could be important for controlling impulse behavior.

His team theorizes that unhealthy eating choices can lead to disrupted brain connections that lead to weakened brain performance, which can lead to making more unhealthy choices.

In other words, it's a vicious cycle.

A second study, presented by Dr. Tony Goldstone, showed the brain's orbitfrontal cortex may play a big role in how people make food choices. This area encodes the "value" of a food, Goldstone said -- i.e. how rewarding or pleasurable it will be to eat.

Study participants were asked to fast overnight. In the morning they were given a breakfast of about 700 calories and shown photos of food while hooked up to an MRI machine. They were asked to fast again before another visit; the following morning they were not given breakfast and then shown the same photos.

The starving participants' orbitfrontal cortex's were activated when they were shown photos of high-calorie food. Their reaction was less strong after they had eaten breakfast.

The research suggests fasting or dieting increases the brain's desire for high-calorie food.

"That's one of the reasons it's so difficult to keep weight off," Goldstone said.

The good news is that research is ongoing to find ways to block our brains' love of unhealthy food. Two studies presented at the conference analyzed the effect of medications designed to treat alcohol/drug addiction on rats' eating behaviors.

In one, researchers injected the addiction drug naltrexone into the prefrontal cortex -- the decision-making area of the brain -- to decrease junk food consumption in binge-eating rodents. The drug worked in the study, but more research is needed to see if and how this could apply to humans.

Copyright 2012 Scripps Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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