Fructose in sugary drinks and even fruit could make on hungrier for high-calorie foods.
A new study looked at how the brain and body react to fructose and glucose in hopes of gaining insight into how these sugars influence brain-reward pathways and the urge to eat, the University of South California reported. Glucose is found in almost every carbohydrate-containing food, and fuels the human body's cells, while fructose is a simple sugar found in fruits and vegetables that is metabolized by the liver.
"Fructose fails to stimulate hormones, like insulin, that are important in helping us feel full," said Kathleen Page, assistant professor of medicine at the Keck School of Medicine of USC.
The researchers found that when a group of participants consumed fructose, it led to greater activity in the brain's reward areas compared to when they consumed glucose. This also led to greater feelings of hunger strong enough to cause participants to turn down a monetary reward.
"We gave the volunteers choices between being served tasty food immediately after the study or having money sent to them one month later," Page said. "When the study participants consumed fructose, they had a greater willingness to give up the money to obtain immediate high-calorie foods, compared to when they consumed glucose."
The participants, who were made up of 24 young men and women, underwent brain scans before eating breakfast as they looked at pictures of delicious food. They also provided blood samples after consuming a drink sweetened with either fructose or glucose, and then vice versa. The researchers measured hormones in the blood samples that control appetite, and rate the participants' brain scans on level of desire for food.
"This allowed us to see how consuming fructose compared to how glucose affected brain, hormone and hunger responses," Page said.
The findings suggest consuming fructose activates brain rewarding and triggers hunger much more strongly than glucose.
"The best way to reduce fructose intake is to decrease the consumption of added sugar sweeteners, which are the main source of fructose in the American diet," Page concluded.
The findings were published in a recent edition of PNAS.
