Not all sugar is alike! (GIF: Getty Images/Priscilla De Castro for Yahoo Health)
If you were given the option to eat junk food or receive money, you’d choose the money, right? It’s practically a no-brainer … or so you’d think.
A small new study out of the University of Southern California shows that people are more willing to choose high-calorie foods over money after ingesting a certain type of sugar.
In the study, researchers conducted brain scans on 24 people who had been given drinks sweetened with fructose on one day and glucose on another. Glucose is the main sugar circulating in our bloodstream, and the sugar used to fuel all of the cells in our body, including our brain. Fructose, on the other hand, is mainly metabolized in the liver and doesn’t stimulate hormones like insulin that let you know that you’re full.
The study participants were then shown images of high-calorie foods like candy, cookies, pizza, and hamburgers, and reported how hungry they felt and how much they wanted those foods.
Participants felt hungrier and showed greater activity in the areas of the brain associated with the reward value of taste and visuals when they saw the food images after ingesting fructose, versus after having the glucose drink.
Researchers also gave participants the option of choosing a delayed monetary reward or immediate high-calorie food reward. After having the fructose drink, people were more willing to give up free money to have the food than they were after they had the glucose drink.
While the study results are surprising, what do they mean, exactly? Lead study author Kathleen Page, MD, assistant professor of medicine at the University of Southern California, tells Yahoo Health that the results suggest fructose may not make people feel as full as they do after having glucose. As a result, they end up feeling so hungry that they’re willing to give up money for food.
Translated to the real world, that means you’re more willing to buy a greater amount of high-calorie foods at the grocery store after you’ve had a soda or junk food.
This isn’t the first research to show that fructose negatively affects our hunger response. A 2013 study published in The Journal of the American Medical Association found that fructose only weakly stimulates the body’s secretion of insulin, which works to increase feelings of fullness and blunt the reward value of food. A study from Harvard Medical School that was published last year in the journal Molecular Metabolism also found that fructose may promote obesity and diabetes by overstimulating a hormone that helps to regulate fat accumulation.
While research has analyzed fructose that was consumed in a sugary drink, fructose occurs naturally in fruits and honey — and it’s not a problem when it’s eaten in moderation, says Jennifer Clemente, certified nutritionist at The Kellman Center in New York City. But fructose in processed foods like soda, packaged foods, prepackaged meals, junk food, and processed sauces is another story. That fructose is often highly concentrated and, after it’s metabolized by the liver, can end up as fat that collects around your midsection and organs.
“This type of fat is dangerous and correlated with a higher risk of heart disease,” Clemente tells Yahoo Health. “It is also turned into free fatty acids and the ‘bad’ cholesterol, VLDL.” Ingesting high levels of fructose, mainly in the form of high-fructose corn syrup, is directly related to a rise in obesity, metabolic syndrome, Type 2 diabetes, high cholesterol, insulin resistance, and liver and heart disease. It can also block your body’s ability to use vitamins and minerals that you take in.
Glucose, on the other hand, comes from a variety of the foods we eat. Carbohydrates like fruit, bread, pasta, and cereals are common sources of glucose, but it’s also found in vegetables and meats. Glucose is essential for your body to function and when your glucose levels drop, you’ll often feel hungry and moody.
Clearly, it’s not a good idea to consume concentrated amounts of fructose. The best way to steer clear, says Page, is to try to avoid foods that have added sugar sweeteners — such as sodas, junk food, and packaged foods — whenever possible.
Your waistline — and your wallet — will thank you.
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