Highly processed carbohydrates can trigger the same brain mechanism associated with substance addiction, researchers from the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital reported in The American Journal of Clinical Nutrition (June 26th, 2013 issue).

In other words, eating high glycemic foods, such as highly processed carbohydrates, can trigger overwhelming hunger and stimulate regions in the brain associated with reward and cravings.

Study leader, David Ludwig, MD, PhD, said cutting down on these high-glycemic foods may help prevent overeating in obese people.

Dr. Ludwig and team had set out to determine whether food consumption might be regulated by dopamine-containing pleasure centers in the brain.

Ludwig said, “Beyond reward and craving, this part of the brain is also linked to substance abuse and dependence, which raises the question as to whether certain foods might be addictive.”

The Glycemic Index measures how fast and by how much food raises levels of blood glucose (sugar). Foods with higher index values (high-glycemic foods) raise blood glucose faster than foods with lower glycemic values.

After we eat, our bodies break down most carbohydrates and convert them to glucose, a type of sugar. Our cells need glucose to survive. Not all carbohydrates are broken down into glucose and released into the bloodstream at the same speed – this depends on the type of carbohydrate we eat.

Examples of high-glycemic foods include most white bread, most white rice, bagels, parsnip, pretzels, corn flakes, glucose, maltose, and potato.

Ludwig and colleagues measured levels of blood glucose and hunger, while at the same time using fMri (functional magnetic resonance imaging) to observe brain activity) to observe brain function. They focused on brain activity during the four-hour period after eating, which drives our eating behavior when we next eat.

The authors explained that theirs is the first study to observe people during this four-hour period. Previous studies only evaluated patients soon after eating with MRI.

What is the difference between MRI and fMRI? – it is a bit like the difference between still photography and video. MRI sees “what is” while fMRI sees “what is going on”. fMRI observes how the brain is functioning.

This latest study included 12 obese or overweight participants. They were given two types of milkshakes, both with the same number of calories, taste and levels of sweetness. However, one contained high-glycemic carbs (carbohydrates) while the other had low-glycemic carbs.

After drinking the high-glycemic milkshake, the volunteers experienced the initial “sugar-rush”, a surge in blood glucose levels, followed by a steep crash four hours later.

The crash in blood sugar levels was accompanied by overwhelming hunger and intense activity within the nucleus accumbens, a region in the brain involved in addictive behaviors.

Previous studies tended to compare high-calorie to low-calorie meals. This one compared meals with the same number of calories, but different glycemic indexes, to determine whether they might affect brain function and make people overeat.

Ludwig said:

“These findings suggest that limiting high-glycemic index carbohydrates like white bread and potatoes could help obese individuals reduce cravings and control the urge to overeat.”

Researchers from Yale University also found that food addiction and substance dependence have similar brain activities. They reported their findings in Archives of General Psychiatry.

Ashley N. Gearhardt, M.S., M.Phil., and colleagues explained that people with addictive-like eating behavior appear to have more neural activity in certain regions of the brain in the same way people with substance abuse seem to have.

It is similar to saying that if you dangle a tasty milkshake in front of somebody who is addicted to eating, what goes on in his/her brain is not very different to what happens in the brain of an alcoholic if you tempt him/her with an alcoholic beverage.

The scientists found a correlation between food addiction and greater activity in the anterior cingulated cortex, amygdala, and medial orbitofrontal cortex when their participants knew that a tasty food delivery would arrive soon.

Researchers at the American University, Washington D.C., reported in The American Journal of Clinical Nutrition (October 2012 issue) that fatty, sugary foods may harm the brain and encourage overeating.

Written by Christian Nordqvist