Scientists have used imaging tests to show for the first time that fructose, a sugar that saturates the American diet, can trigger brain changes that may lead to overeating. After drinking a fructose beverage, the brain doesn't register the feeling of being full as it does when simple glucose is consumed, researchers found. It's a small study and does not prove that fructose or its relative, high-fructose corn syrup, can cause obesity, but experts say it adds evidence these sugars may play a role.
For the study, scientists used MRI scans to track blood flow in the brain in 20 young, normal-weight people before and after they had drinks containing glucose or fructose in two sessions several weeks apart. Scans showed that drinking glucose "turns off or suppresses the activity of areas of the brain that are critical for reward and desire for food," said one study leader. With fructose, "we don't see those changes," he said. "As a result, the desire to eat continues." The imaging results mirrored how hungry the people said they felt, as well as what earlier studies found in animals. Researchers now are testing obese people to see if they react the same way.