America without a doubt is one of the most obese nations on earth.
A new study published in the American Journal of Clinical Nutrition has shed a light on why the obesity epidemic exists suggesting that consuming highly processes carbohydrates can cause excess hunger and stimulate brain regions involved in reward and cravings. These foods are considered to be high glycemic index foods and limited their consumption may assist individuals from over eating.
The food intake is regulated by the dopamine containing 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,” says Ludwig a lead author of the study.
To directly examine the causal 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. Evaluating patients in this time frame is one novel aspect of this study, whereas previous studies have evaluated patients with an MRI soon after eating.
Twelve overweight or obese men consumed test meals designed as milkshakes with the same calories, taste and sweetness. The two milkshakes were essentially the same; the only difference was that one contained rapidly digesting (high-glycemic index) carbohydrates and the other slowly digesting (low-glycemic index) carbohydrates.
After participants consumed the high-glycemic index milkshake, they experienced an initial surge in blood sugar levels, followed by 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.
“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.
Belinda S Lennerz, David C Alsop, Laura M Holsen, Emily Stern, Rafael Rojas, Cara B Ebbeling, Jill M Goldstein, and David S Ludwig. Effects of dietary glycemic index on brain regions related to reward and craving in men. Am J Clin Nutr, June 26, 2013 DOI: 10.3945/ajcn.113.064113