Scientists have used magnetic resonance imaging to show for the first time that fructose can trigger brain changes that may lead to overeating.
Researchers found that after drinking a beverage containing fructose, the brain doesn’t record the feeling of being full as it does when simple glucose is consumed.
Although sugar in its various forms may contain the same amount of calories, they are metabolized differently in the body.
An extra metabolic step for fructose molecules is missing in high-fructose corn syrup which is why the excess fructose is metabolized to produce fat. Glucose, on the other hand, is processed for energy or stored as a carbohydrate called glycogen in the liver and muscles.
Table sugar is sucrose, which is half fructose, half glucose. High-fructose corn syrup is 55 percent fructose and 45 percent glucose, and some nutrition experts say this sweetener may pose special risks.
“Fructose and high-fructose corn syrup are added to virtually all processed foods and beverages, and consumption has risen dramatically since the 1970s along with obesity. A third of U.S. children and teens and more than two-thirds of adults are obese or overweight.”
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, Yale University endocrinologist Dr. Robert Sherwin.
With fructose, “we don’t see those changes,” he said. “As a result, the desire to eat continues – it isn’t turned off.”
What’s convincing, said Dr. Jonathan Purnell, an endocrinologist at Oregon Health & Science University, is that the imaging results mirrored how hungry the people said they felt, as well as what earlier studies found in animals.
“It implies that fructose, at least with regards to promoting food intake and weight gain, is a bad actor compared to glucose,” said Purnell. He wrote a commentary that appears with the federally funded study in Wednesday’s Journal of the American Medical Association.
Last year, a study conducted by researchers at the University of California Los Angeles revealed that a steady diet of high-fructose corn syrup slows the brain, and impairs memory and learning.
The study also showed that omega-3 fatty acids — mainly found in fish and some fruits and vegetables — can counteract the memory and learning disruption caused by elevated levels of high-fructose corn syrup.
“Our findings illustrate that what you eat affects how you think,” said Fernando Gomez-Pinilla, a professor of neurosurgery at the David Geffen School of Medicine at UCLA and a professor of integrative biology and physiology in the UCLA College of Letters and Science.
“Eating a high-fructose diet over the long term alters your brain’s ability to learn and remember information. But adding omega-3 fatty acids to your meals can help minimize the damage.”