According to WebMD, only eating fruit for a certain amount of time can lead to weight loss. The Fruit Flush Diet can cause nine pounds of weight loss in three days. Much of this, however, is water, and the weight is likely to come back after the diet ends.
WebMD adds that eating only, or mostly, fruit can be healthy, since most Americans do not get enough fruits and vegetables in their regular diets. However, the key to sustained weight loss is a commitment to a continued change in eating habits, not restriction to a certain kind of food for a short period of time.