Excessive carbohydrate consumption causes the insulin level in the blood to increase, which reduces the blood sugar level. Research suggests that a decrease in blood sugar stimulates hunger and thus there is an intense desire to eat more food. Through functional magnetic resonance imaging, researchers observed intense activation of the nucleus accumbens (a critical brain region involved with addictive behaviors) after participants consumed a carbohydrate-rich food with a high glycemic index. Chronic, excessive consumption of the latter food type may trigger the reward and addiction regions of the brain leading to food cravings.