The type of sugar you eat may trigger fullness—or cravings for more food

April 4, 2018 by Constance Sommer, University of Southern California
Fructose, found in fruits and vegetables, is a form of sugar that may trigger cravings while still leaving you hungry. Credit: Photo/iStock

Sugar gets a lot of bad press, and for good reason. Too much of it increases the risk of obesity, diabetes, heart attack and stroke. And Americans tend to eat a lot of it—more than 60 percent blow through the government's recommended consumption on a daily basis.

But is also a naturally occurring substance. In the form of glucose, it shows up in pasta, bread and other carbohydrates. As fructose, we encounter it in fruits and vegetables. How, then, can it wreak so much havoc on our bodies? Keck School of Medicine of USC physician Kathleen Page has been asking this question in the lab, and she's come up with an intriguing answer: Even though your sweet tooth might love all sugar, our brain knows sugars are not equal and responds accordingly.

An experiment: Fructose vs. glucose

Page, who specializes in diabetes and childhood obesity, recruited 24 healthy young women and men for her experiment. One morning, before eating breakfast, they came into the lab and consumed a drink sweetened with glucose. Another morning, they consumed a drink sweetened with fructose. On the day they drank , the volunteers felt more satiated; when they drank fructose, they stayed hungry and craved more food.

So, what does this mean for an average person's diet? Well, it's not a reason to cut back on fruits and vegetables. The fiber, water and general chewiness of, say, an apple or a stick of celery takes a while for the body to digest, and so the fructose hits the system slowly. In contrast, the fructose in a can of soda or glass of O.J. "goes straight to your bloodstream," Page said, "because there's nothing to slow down the absorption."

Fructose vs. glucose vs. corn syrup vs. honey

The kind of sugar in soft drinks is the much-demonized high fructose corn syrup. But any form of added sugar—sweeteners added during processing, be it white sugar, brown sugar, , corn syrup or even honey—seems to deliver that same addictive jolt to your brain that leaves you wanting more, Page said. The key word is "seems." Scientists have fed sugar to animals, and found that it triggers cravings and withdrawal behaviors similar to those found with drug addiction. But such trials have been difficult to replicate with humans. "It's very hard to control people's access to sugar," Page said.

The problem is that added sugars are everywhere. Not just in brownies or soda, but hidden in places you might not suspect, like ketchup, bread, salad dressing and crackers. Watch out particularly for yogurts with flavoring or fruit at the bottom. "People think yogurts are healthy but they have tons of sugar," Page said. For instance, a 5.3 ounce container of Trader Joe's Nonfat Black Raspberry Greek Yogurt has 15 grams of sugar. Even when accounting for the naturally occurring sugars in the fruit, that's still a hefty chunk of the recommended 25 grams of added sugar per day (or 6 teaspoons) for women, and 36 grams (or 9 teaspoons) for men.

Check the ingredients

Be thoughtful and savvy with everyday marketing and eating, Page suggests. Remember that any food that has no fruit or milk in the ingredient list gets its sweetness from added sugars. At the grocery store, check ingredient labels. "The closer the sugars are to the top of the list, the higher the that food has." Try not to keep sodas in the house – or, for that matter, fruit juices, which have all the sugar of fruit without the fiber and chewiness that slows down the delivery.

And instead of cutting yourself off cold turkey, try to ease into it. "It's difficult to completely deprive yourself of dessert," Page said. And know that, particularly if you have a , you will probably struggle at first to cut back on sugar, not because you lack willpower – but because sugar is designed that way.

Explore further: Can eating sugar cause cancer?

Related Stories

Can eating sugar cause cancer?

January 8, 2018
A recent study published by Belgian biologists found a relationship between glucose (sugar) and the activation of a gene that stimulates the growth of cancer cells. This led to public fear that everything with sugar should ...

Researchers examine how the brain and body respond to glucose and fructose

May 5, 2015
When it comes to sweeteners, one indulgence makes our brains predisposed to do it, according to a new study by researchers at Keck Medicine of USC.

How rare sugars might help control blood glucose

March 8, 2017
In an era when the label "natural" hits a sweet spot with consumers, some uncommon sugars emerging on the market could live up to the connotation. Preliminary animal studies have suggested that allulose and other low-calorie, ...

Fructose is generated in the human brain

February 23, 2017
Fructose, a form of sugar linked to obesity and diabetes, is converted in the human brain from glucose, according to a new Yale study. The finding raises questions about fructose's effects on the brain and eating behavior.

Eliminate sweetened drinks, cut kids' sugar intake

September 26, 2016
(HealthDay)—Looking for the quickest way to cut added sugar from your kid's diet?

Recommended for you

Widespread declines in life expectancy across high income countries coincide with rising young adult, midlife mortality

August 15, 2018
The ongoing opioid epidemic in the United States is a key contributor to the most recent declines in life expectancy, suggests a study published by The BMJ today.

Diets high in vegetables and fish may lower risk of multiple sclerosis

August 15, 2018
People who consume a diet high in vegetables and fish may have a reduced risk of multiple sclerosis, new research led by Curtin University has found.

Can sleeping too much lead to an early death?

August 15, 2018
A recent study in the Journal of the American Heart Association has led to headlines that will make you rethink your Saturday morning sleep in.

Parental life span predicts daughters living to 90 without chronic disease or disability

August 15, 2018
Researchers at the University of California San Diego School of Medicine report that women whose mothers lived to at least age 90 were more likely to also live to 90, free of serious diseases and disabilities.

Mixing energy drinks with alcohol could enhance the negative effects of binge drinking

August 14, 2018
A key ingredient of energy drinks could be exacerbating some of the negative effects of binge drinking according to a new study.

New study finds fake, low-quality medicines prevalent in the developing world

August 10, 2018
A new study from the University of North Carolina at Chapel Hill found that substandard and falsified medicines, including medicines to treat malaria, are a serious problem in much of the world. In low- and middle-income ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.