A team led by David Ludwig, MD, PhD, director of the New Balance Foundation Obesity Prevention Center 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 findings suggest that limiting such “high-glycemic index” foods could help obese individuals avoid overeating.
Published this week in The American Journal of Clinical Nutrition, the study investigated how food intake is regulated by 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.
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.)
The proof is in the milkshake
Twelve overweight or obese men consumed test meals designed as milkshakes with the same calories, taste and sweetness. The only difference was that one contained rapidly digesting (high-glycemic index) carbohydrates and the other contained slowly digesting (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 findings suggest that more interventional and observational studies should be done. Additional research will hopefully inform clinicians about the subjective experience of food addiction, and how we can potentially treat these patients and regulate their weight.
Lennerz BS, Alsop DC, Holsen LM, Stern E, Rojas R, Ebbeling CB, Goldstein JM, & Ludwig DS (2013). Effects of dietary glycemic index on brain regions related to reward and craving in men. The American journal of clinical nutrition PMID: 23803881