A recent study found that when obese adults consumed half a grapefruit or 4 ounces of 100 percent grapefruit juice before three main meals, they experienced a significant decrease in both body weight and waist circumference. This may be due to the high water content of the grapefruit helping them to feel satisfied and reduce their portions of other foods.
One extra belly fat–fighting benefit of grapefruit: It contains diuretic properties, helping you shed unwanted water weight, that bloats your belly.