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. Our brains consist of a complex network of pathways and regions that control all our bodily functions. Chemical messengers called neurotransmitters allow signals to pass from one nerve cell to the next to aid in these functions. One neurotransmitter, dopamine, plays a major role in the brain’s reward pathways. For example, the brain gets flooded with dopamine whenpeople take addictive drugs including cocaine and nicotine.
To find out how food intake was regulated by the dopamine-reward pathway, researchers recruited 12 overweight or obese men between the ages of 18 and 35 years old. On two occasions, they were fed milkshakes that were almost identical except one had a high glycemic index and one was low glycemic (the glycemic index measures how fast blood sugar levels rise after eating that item) Four hours after the meals, they were given fMRI brain scans that measured activity of these brain networks and pathways. Participants who drank the high glycemic milkshakes saw their blood sugar levels surge, only to sharply crash four hours later. When their blood sugar dropped, not only did they feel excessive hunger, but the fMRIs showed “intense” activation in the nucleus accumbens, a region of the brain involved in addiction.
These findings suggest that limiting high glycemic index carbohydrates like sweets, white bread and potatoes could help obese individuals reduce cravings and control the urge to overeat.
Adapted from the Harvard School of Public Health