Grapefruit Juice Curbs Weight Gain

Eating grapefruit or drinking grapefruit juice may help to prevent weight gain and  increase insulin sensitivity. Andreas Stahl and Joseph Napoli of the University of California Berkeley and colleagues randomly assigned mice to receive drinking water alone (control) or drinking water containing either 50% grapefruit juice, 25% grapefruit juice, naringin (a bioactive compound in grapefruit juice that has been identified as a key agent in weight loss), the glucose-lowering drug metformin, or a combination of metformin and grapefruit juice. Saccharin was also added to the mixture to counteract grapefruit's bitterness. The researchers also added glucose and artificial sweeteners to the control group's water so that it would match the calorie and saccharin content of the grapefruit juice. The mice were fed a diet that was either 60% fat or 10% fat for 100-days, and their metabolic health was monitored throughout the study. Results showed that mice that ate the high-fat diet and drank diluted grapefruit juice not only gained less weight than their control counterparts, but also exhibited a 13-17% decrease in blood glucose levels and a threefold decrease in insulin levels, thus suggesting that grapefruit boosts insulin sensitivity. The results of the mice fed naringin or metformin were especially promising. "The grapefruit juice lowered blood glucose to the same degree as metformin," said Dr Napoli, professor and chair of nutritional sciences and toxicology. "That means a natural fruit drink lowered glucose levels as effectively as a prescription drug." Although naringin had a significant effect upon blood glucose levels it had no effect on weight, suggesting that some other ingredient in grapefruit juice is also beneficial.