The next time you go out for cheeseburgers or pepperoni pizza, you might want to consider washing it down with a glass of grapefruit juice.

A study from the University of California, Berkeley researchers found that mice that drank their fill of sweetened grapefruit juice gained less weight on a high-fat diet than their counterparts that drank sweetened water. The juice-drinking mice also had better measures of metabolic health, including blood sugar levels and insulin sensitivity.

The findings, published Wednesday in the journal PLOS One, come with several caveats. The study was paid for by the California Grapefruit Growers Cooperative. But the Berkeley researchers, from the university's Department of Nutritional Sciences and Toxicology, insisted that they went into the study with plenty of skepticism.

"I was surprised by the findings," Andreas Stahl, the study's senior author, said in a statement from the university. "We even re-checked the calibration of our glucose sensors, and we got the same results over and over again."

Also, the study was small, with each combination of diet, liquid and other nutrients tested in groups of just six mice.

Still, the results may help explain why grapefruits are frequently featured in fad diets.

After eating high-fat chow for 100 days, the mice that drank grapefruit juice weighed 18.4 percent less than the mice that drank the sweetened water.

At the end of the 100 days, the mice that drank juice were in better metabolic health than the ones that drank the same amount of calories in the form of sugar water. They had lower fasting blood sugar levels, better insulin sensitivity and lower levels of triglycerides in their livers.

In a follow-up experiment, the researchers allowed the mice to become obese before they introduced the grapefruit juice. After 55 days, the mice that drank grapefruit juice weighed 8 percent less than the mice that drank water, and they also showed signs of better metabolic function.

It's not exactly clear why grapefruit juice would promote weight loss. However, the researchers noted that mice that drank juice had reduced expression of a protein involved in regulating metabolism, so perhaps something in grapefruit changes the way the body makes or stores fat.

The researchers also warned that grapefruit and grapefruit juice may interfere with the body's ability to metabolize certain drugs.

This list includes some kinds of drugs taken to control cholesterol, blood pressure, heart arrhythmia, allergies and anxiety, according to the Food and Drug Administration. The problem is serious enough that scientists are trying to create a hybrid grapefruit that would be safe to take with medications, this FDA video says.


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