Researchers used functional ("real time") MRI to observe the brain activity of 12 overweight or obese men during the crucial four hours after they ate a meal, a period that experts say influences eating behaviour during the next meal.
The participants' blood sugar levels and hunger were also measured during this time.
The men's "meals" were two milkshakes that had the same kilojoules, taste and sweetness. The only difference was that one milkshake contained high-glycaemic index carbohydrates and the other had low-glycaemic index carbohydrates.
High-glycaemic index carbohydrates -- which are quickly transformed into sugar in the blood -- are found in highly processed foods such as white bread and white rice. Low-glycaemic index carbohydrates are found in items such as whole wheat products and sweet potatoes.
What the study found
The researchers found that consuming carbohydrates like those found in processed foods can cause excess hunger and stimulate areas of the brain involved in reward and cravings, regions that also play a role in addiction, according to the study published June 26 in the American Journal of Clinical Nutrition.
The study might have implications for weight control, the researchers said.
"Limiting high-glycaemic index carbohydrates like white bread and potatoes could help obese individuals reduce cravings and control the urge to overeat," study leader Dr David Ludwig, director of the obesity prevention centre at Boston Children's Hospital, said in a hospital news release.
The Harvard School of Public Health has more about carbohydrates.