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Addicted to … Food?

High-glycemic foods and substance abuse may engage the same brain mechanism

By ANDREA MOONEY
July 3, 2013

A study of 12 men found that glycemic load—distinct from calories or sweetness—can alter brain function and promote overeating. Image: iStock

Is there such a thing as food addiction? A study using brain imaging suggests that high-glycemic foods may trigger the same brain mechanism as substance abuse.

A team led by David Ludwig, HMS professor of pediatrics at Boston Children’s Hospital, found that consuming highly processed, rapidly digested carbohydrates can cause excess hunger and stimulate brain regions involved in reward and cravings. These results suggest that limiting these high-glycemic-index foods—“bad carbs” such as white bread and potatoes—could help obese people avoid overeating.

Published recently in The American Journal of Clinical Nutrition, the study investigated how food intake is regulated by the pleasure centers of the brain.

“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,” said Ludwig, who is also director of the New Balance Foundation Obesity Prevention Center at the hospital.

To examine the link, researchers measured blood glucose levels and hunger, while also using functional magnetic resonance imaging (MRI) to observe brain activity during the crucial four-hour period after a meal, which influences eating behavior at the next meal. (Previous studies have tended to evaluate patients with MRI soon after eating.)

On two occasions, 12 overweight or obese men consumed two test meals delivered as milkshakes with the same taste, sweetness and number of calories. One milkshake contained rapidly digestible (high-glycemic index) carbohydrates and the other contained slowly digestible (low-glycemic index) carbohydrates.

After the men consumed the high-glycemic index milkshake, they had an initial surge in blood sugar levels, followed by a sharp crash four hours later. This decrease in blood glucose was associated with excessive hunger and intense activation of the nucleus accumbens, a critical brain region involved in addictive behaviors.

Prior studies of food addiction have compared patient reactions to drastically different types of foods, such as high-calorie cheesecake versus boiled vegetables. This study narrows the difference to one variable only—the glycemic load—and indicates that this factor, distinct from calories or sweetness, can alter brain function and promote overeating.

“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,” says Ludwig.

Though the concept of food addiction remains provocative, the authors recommended that more interventional and observational studies should be done. Additional research could inform clinicians about the subjective experience of food addiction, and how to potentially treat these patients and regulate their weight.

Adapted from a Boston Children’s Hospital news story.

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