The "grapefruit diet" was a popular way to lose weight back in the 1990s. Although fad diets are generally unhealthy and ineffective, one aspect of the grapefruit diet was on to something: Eating grapefruit or drinking grapefruit juice, as part of a healthy lifestyle, can help you lose weight. Grapefruit juice may help to lower insulin levels, which makes it easier to keep the pounds off.
A study of 100 men and women by the Scripps Clinic in San Diego, California, found that participants who drank grapefruit juice three times a day lost an average of 3.3 pounds. Some participants lost more than 10 pounds.
Researchers believe the positive weight-loss effects of grapefruit juice happen because it lowers insulin levels. Insulin is a hormone that regulates the absorption of glucose, or sugar, in the body; excess insulin in the body can cause weight gain. If you have high insulin levels and are already following a diet and exercise plan, adding grapefruit juice can help.
Juice vs. Fruit
Although juice is a more convenient way to get grapefruit into your diet, you may want to consider eating the whole fruit instead. In the Scripps Clinic study, those who ate half a grapefruit with each meal lost 0.3 pounds more than the juice drinkers. Fruit juices in general contain a lot of sugar -- though grapefruit juice in particular isn't as sweet as other juices -- and lack the fiber found in the whole fruit, which may explain the increase in weight loss by the fruit eaters.