Health & Wellness

Why We Crave Junk Food

Before you rip open a bag of chips or reach for a jelly doughnut, take heed. If you want to lose weight, you’ll have to expend more calories than you take in.

“There’s no way around this equation,” says Utah State University neurobiologist Timothy Gilbertson. “Don’t believe product claims that promise to melt away fat. It’s impossible.”

Gilbertson, professor and associate head of USU’s Biology Department and associate director of the university’s Center for Advanced Nutrition, has long studied how the body recognizes and responds to nutrients. His research reveals that certain fats activate receptors in our bodies that make sweet and salty foods taste better.

“Until recently, scientists believed that fat had mouth feel but no taste,” says Gilbertson. “But it does have a taste, which impacts why we choose to eat the foods we do.”

Craving and storing fat was critical for our Paleolithic ancestors’ survival but creates a formidable health challenge in our current era of plentiful food and leisure, he says. Based on studies he’s conducted with rats, Gilbertson believes the more fat we eat the less sensitive our fat receptors become, which causes us to crave even more fat.

In Gilbertson’s experiments with sibling rats, one was given a normal diet and the other a high-fat diet. As expected, the rat that ate more fat became fatter. But when researchers switched the fat rat to a normal diet, the rat, apparently unsatisfied, ate more than her normal weight sister. Months passed before the fat rat reduced her intake.

“We think this has implications for why dieting is so hard for people,” he says.

What about claims that certain people are genetically disposed to obesity?

“Obesity linked directly to genes accounts for only about five percent of cases and about five to seven percent of cases are caused by metabolic disorders,” says Gilbertson.

For the vast majority of people, he says, obesity is caused by lifestyle choices. “We eat too much and exercise too little.”

And the result is alarming. Obesity trends in the United States are spiraling upward. The rest of the world is following suit.
“One in three Americans is now obese, which has serious health consequences,” says Gilbertson. “Obesity places people at direct risk of hypertension, diabetes, heart disease and cancer.”

There’s no magic solution, says Gilbertson, who advocates efforts to educate children at an early age about healthy eating and exercise habits. If children eat a high-fat diet before age 10, he says, “We’re pushing them down the same path as that (fat) rat.”

Contact: Tim Gilbertson,, 435-797-2578
Writer: Mary-Ann Muffoletto,, 435-797-1429
January 2008

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Tim Gilbertson

Research led by USU neurobiologist Tim Gilbertson focuses on how our bodies recognize and respond to nutrients.

sibling rats

Gilbertson's research with sibling rats revealed the long-term consequences of a high-fat diet.


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