The amount of weight loss on an all-liquid diet depends on the number of calories in the diet and the starting weight of the person dieting. Most doctors do not recommend liquid diets because the weight lost usually returns once the diet is over, according to WebMD.
Any diet that takes in fewer calories than is expended results in weight loss; however, many liquid diets are deficient in the vitamins and minerals needed for good health. Potential side effects of low-calorie liquid diets include fatigue, dizziness, hair loss, gallstones and heart damage. Diets that combine liquid meals with solid foods are more effective for lasting weight loss than all-liquid diets, according to WebMD.