Conducted by principal investigator Kathleen Page, assistant professor of medicine at the Keck School, the research determined that fructose and glucose, the two forms of simple sugars, are processed differently in the brain. The difference was apparent after study participants consumed drinks containing fructose or glucose and is a potential explanation for why people gain weight.
“We saw that fructose did not cause feelings of fullness, whereas the participants reported an increase in feelings of fullness after the glucose drink,” said Page, who is also chair of the Maternal-Child Health section of the USC Diabetes and Obesity Research Institute.
The research was published in the Journal of the American Medical Association and was conducted while Page was on faculty at Yale.
The study used functional magnetic resonance imaging to map changes in the brains of 20 test subjects who consumed sugary drinks.
The researchers found that the glucose drink suppressed activity in the hypothalamus and other brain regions that regulate appetite, motivation and reward processing, while the fructose drink did not. The different responses to fructose were associated with reduced levels of the hormone insulin, which sends signals to the brain that a person has had enough to eat.
Fructose, found with glucose in many fruits and vegetables, as well as table sugar, is an ingredient in high-fructose corn syrup, a popular sweetener. High-fructose corn syrup is found in certain soft drinks and processed foods, and consumption of the sweetener has been on the rise over the past few decades. Rates of obesity have increased in parallel, the researchers noted.
In continuing research, Page’s team is studying whether obese people have exaggerated brain reward and hunger responses to fructose and whether different ethnic groups respond differently to fructose and glucose.
Research funding was provided by the Doris Duke Charitable Foundation.