Eating some types of sugar rather than others leaves you feeling hungrier and with less self-control when it comes to making decisions about food, a study out of the US indicates.
Anti-sugar advocates have long blamed a type of sugar called fructose for many of our nutritional woes.
Different types of sugar have different effects on our bodies, a study has shown. Photo: Andrew Quilty
One Australian expert says this new research shows how fructose “gets under the satiety radar”, importing calories without sending signals to our body that we have eaten.
Study leader Kathleen Page, a doctor and an assistant professor of medicine at the Keck School of Medicine at the University of Southern California, said her research could have important public health implications because it essentially showed that fructose may encourage “feeding behaviour”.
In her study, 24 volunteers were asked to drink fructose and glucose drinks, and afterwards were subjected to a range of different tests to see the effect the different sugars were having on their bodies.
The tests included measuring insulin and other eating-related hormones in the blood, as well as rating their hunger, and scanning their brains for activity while they looked at images of food and showing them images of high-energy foods and offering them the choice of having the food now or a monetary reward later.
Professor Page said on average the fructose group were willing to give up about $US1.45 ($1.85) in payments in order to eat the foods presented to them – and one participant even went as high as forgoing $20 in payments to get the food.
The different ways glucose and fructose affect insulin. Graph: Proceedings of the National Academy of Sciences
“Ingestion of fructose versus glucose also led to greater hunger and desire for food and a greater willingness to give up long-term monetary rewards to obtain immediate high-calorie foods,” the authors wrote in the prestigious journal Proceedings of the National Academy of Sciences. “Ingestion of fructose relative to glucose [also] activates brain regions involved in attention and reward processing and may promote feeding behaviour.”
Kerin O’Dea, a professor of population health and nutrition at the University of South Australia, said the findings were not just important for fructose, but for sugar more generally.
Table sugar, or cane sugar, is technically known as sucrose, a molecule that is half glucose and half fructose. But the fructose is what really gives the sweet flavour.
Professor O’Dea said sugar was also often added to foods that did not even need to be particularly sweet, such as peanut butter.
“Why does the industry add sucrose to foods that aren’t sweet? Somehow it stimulates appetite, and this is probably the mechanism,” she said.
“I have said … for years now that fructose essentially gets under the satiety radar, and this is proof,” she said. “What this study shows is that if you consume 50 grams of fructose it will only produce about half the amount of insulin as you would get with 50 grams of glucose, and insulin going to the brain is part of the satiety process.”
She said while many people pushed the idea that drinks and other products sweetened with high-fructose corn syrup were the real problem because it contains about 65 per cent fructose, in reality that was “not that much more” than normal sugar.