MRI Shows Fructose Changes The Brain and May Cause Overeating



Don Farrall/Thinkstock
Don Farrall/Thinkstock
In a recent study released by the Journal of the American Medical Association, researchers used imaging tests to show that fructose triggers brain changes that may lead to overeating in a way that glucose does not. It’s a theory that faces a lot of criticism but certainly brings up questions.


After drinking a fructose beverage, the brain doesn’t register the feeling of being full in the same way it does with glucose. This was a small study and experts have by no means fully accepted the claim, but many contend that fructose may play a role in obesity, according to MyFoxDC.

Researchers gave 20 young, normal weight participants drinks containing glucose or fructose in sessions that were weeks apart. They used MRI scans to follow blood flow in the brain. 

Your Brain on Sugar

According to the study:

Increases in fructose consumption have paralleled the increasing prevalence of obesity, and high-fructose diets are thought to promote weight gain and insulin resistance. Fructose ingestion produces smaller increases in circulating satiety hormones compared with glucose ingestion, and central administration of fructose provokes feeding in rodents, whereas centrally administered glucose promotes satiety.

Fructose Sources

Glucose consumption seemed to promote satiety while fructose did not. Sugar is half glucose and half fructose. But it's a bit confusing because fructose is found in plant sources like honey, tree and vine fruits, flowers, berries, and most root vegetables. But in fruit it's also combined with fiber, which fills you up. 

Its natural sources don't create near the issues that its processed state seems to produce. Fructose is added to beverages and processed foods in the U.S. in the form of high fructose corn syrup. The process starts off with corn kernels that are spun at a high velocity and combined with three other enzymes: alpha-amylase, glucoamylase, and xylose isomerase, so that it forms a thick syrup that's way sweeter than sugar and super cheap to produce. 

According to MyFoxDC:

Scans showed that drinking glucose "turns off or suppresses the activity of areas of the brain that are critical for reward and desire for food," said one study leader, Yale University endocrinologist Dr. Robert Sherwin. With fructose, "we don't see those changes," he said. "As a result, the desire to eat continues - it isn't turned off."

I’ve written before that high fructose corn syrup interferes with the body's metabolism so that a person can't stop eating. It's truly hard to control cravings because high fructose corn syrup slows down the secretion of leptin in the body. Leptin is a crucial hormone that tells you you're full and to stop eating. 

It's an area of study where much more research is sure to come, but either way, limiting your sugar consumption is always a good idea. 


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Sara Novak writes about health and wellness for Discovery Health. Her work is also regularly featured in Breathe Magazine and on She has written extensively on food policy, food politics, and food safety.









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