Vitality

Your Brain Responds Differently To Fructose Than Glucose And Causes You To Want To Eat

sugar
Fructose amplifies the reward circuits in your brain, causing you to want to eat whenever you see a food cue, such as a commercial on TV. Photo courtesy of Shutterstock.

Not all sugars are the same. According to research presented today at the annual meeting of the American College of Neuropsychopharmacology, your brain responds differently to two types of sugar. Fructose amplifies the reward circuits in your brain, causing you to want to eat whenever you see a food cue, such as a commercial on TV. However, your brain responds to glucose in a less dramatic way and also causes an opposite effect: you feel sated (full), not hungry, when you see an image of food.

Such opposite reactions can make all the difference in the world if you are battling obesity or wanting to lose weight.

Technically, there are three types of simple sugar: glucose, fructose, and galactose, which is not usually added to commercially processed foods as it is not as sweet. Glucose is the body’s primary source of energy and is usually produced through the breakdown of complex carbohydrates. Foods high in glucose include dried fruits, fresh fruits, and to a lesser extent grains, beans, vegetables, and nuts. While the same foods, especially fruit, also contain fructose, this type of simple sugar is added to many processed foods in the form of high-fructose corn syrup.

Scientific studies have shown that glucose reduces activity in the region of the brain known as the hypothalamus, whereas fructose does not. The hypothalamus controls hunger and thirst, among other metabolic processes. Compared to glucose, eating fructose also has been found to produce a smaller increase in satiety hormones. Finally, when fructose is delivered directly to the brains of rats they begin to feed, whereas given glucose in the same way, they act as if sated.

For the current experiment, Dr. Kathleen Page at the Keck School of Medicine and her colleagues at USC used fMRI brain scans to expand on these previous scientific studies. The researchers began by enrolling 24 men and women, between the ages of 16 and 25, as volunteers. Next, the 24 volunteers drank a beverage containing either glucose or fructose. While they viewed images of food (like chocolate cake), the researchers took fMRI scans of their brains. With each new image, the volunteers reported how much they wanted to eat.

What did the researchers discover?

The food cues produced activation in the nucleus accumbens, a part of the brain's "reward circuit." However, activation in the nucleus accumbens was greater after consuming the fructose drink than after the glucose drink. The fructose drink also resulted in higher ratings of hunger and motivation to eat compared to the glucose drink.

About two out of three adults in the United States are overweight and one in three is obese. While adjusting both diet and lifestyle may be necessary to reverse this pattern, a simple trick like avoiding fructose consumption, whenever possible, may make things much easier for those wanting to change.

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