Healthy Living

Eating A High-Fat Diet? Grapefruit Juice May Help You Lose Weight And Decrease Blood Sugar

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A new study finds mice who ate a high-fat diet while drinking grapefruit juice gained 18 percent less weight compared to a group of mice who ate the same but drank only water. Photo courtesy of Shutterstock.

If you yourself have never heard of the legendary grapefruit diet, then most certainly your mother has, and she will be delighted (or dismayed) to learn grapefruit’s time has come again. Or so new research from UC Berkeley might have us believe.

Their new study finds mice who ate a high-fat diet while drinking no-pulp grapefruit juice gained 18 percent less weight compared to a control group of mice who ate the same but drank only water. "Obesity and insulin resistance are such huge problems in our society," said Dr. Andreas Stahl, a professor and co-author of the published research. Though he cautioned these results do not prove humans will benefit in the same manner, he added the new data "provide impetus to carry out more studies."

The Benefits of Grapefruit Juice

The experiment worked like this: The researchers divided mice into six groups, including a control group that drank only water. The grapefruit juice was squeezed from fresh fruit, centrifuged to remove the pulp, diluted with water at different concentrations, and then sweetened slightly with saccharin to counteract the bitter taste, which the mice could not tolerate. To match the calories and saccharin content of this juice, the researchers added equivalent glucose and artificial sweeteners to the control group's water.

The mice ate a diet of either 60 percent fat or 10 percent fat for 100 days, with the researchers making sure ingested calories totaled the same for all. Activity levels and body temperatures were also comparable, and the researchers even measured calories eliminated in feces to check for problems with the mice’s absorption rates. Meanwhile, the researchers monitored the metabolic health of all the mice throughout the study.

How did the mice fare? After 100 days, the mice who ate a high-fat diet while drinking diluted grapefruit juice not only gained 18 percent less weight than their counterparts, they also showed a 13 to 17 percent decrease in blood glucose levels and a three-fold decrease in insulin levels. In one group of mice, the researchers substituted naringin, a bioactive compound in grapefruit juice identified as a key agent in weight loss, for the juice; in another group, they substituted metformin, a glucose-lowering drug often prescribed for those with Type 2 diabetes. The group of high-fat-diet mice who received naringin had lower blood glucose levels than the control group, but there was no effect on weight, which suggests some other ingredient in grapefruit juice is also beneficial. However, a major surprise awaited the researchers.

"The grapefruit juice lowered blood glucose to the same degree as metformin," said Dr. Joseph Napoli, a professor at UC Berkeley and chair of nutritional sciences and toxicology. "That means a natural fruit drink lowered glucose levels as effectively as a prescription drug."

Other results were less surprising; The mice who ate a low-fat diet and drank grapefruit juice saw a two-fold decrease in insulin levels, but no significant change in weight. The cry throughout the land is loud and clear: more studies! See if this works as well in humans!

Source: Chucnovskiy R, Thompson A, Tharp K, Hellerstein M, Napoli JL, Stahl A. Consumption of Clarified Grapefruit Juice Ameliorates High-Fat Diet Induced Insulin Resistance and Weight Gain in Mice. PLOS One. 2014.

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