Foods like pizza, milk chocolate and doughnuts—items loaded with carbohydrates that the body digests quickly—set off the same reaction in the brains of overweight men as gambling or heroin do with addicts, according to a new study.
Researchers at the Boston Children's Hospital recruited 12 overweight or obese men for the study. They gave the men similar milkshakes to drink that were almost identical but differed in one respect.
Each shake had the same calories, sweetness and taste, but contained a different type of carbohydrate than the other. One shake had high-glycemic index carbs, found in highly refined foods like white bread and pizza. These carbs are digested quickly and spike blood sugar levels. The other shake contained a sweetener that takes the body longer to digest and has less of an effect on blood sugar levels.
Four hours after each session the men’s brains were scanned to see what regions of the brain were most active. The subjects who drank the shake with the fast acting carbs had an initial spike in blood sugar, followed by a blood sugar crash. And their brain activity—centered in the right nucleus accumbens, a portion of the brain associated with pleasure and addiction—was similar to that of subjects on heroin. Subjects who drank the low-index shake had lower activity levels in the accumbens region.
These patterns were consistent with earlier findings that the accumbens is activated by the neurotransmitter dopamine, which is released by activities such as sex, gambling, and eating.
In short, a carbodyrate high seems to be real—and potentially addictive. The researchers hope that limiting high-glycemic carbs may reduce food cravings among people prone to overeating.