Like some milkshakes and meal replacement powder, in fact, they all lose weight by controlling the total energy intake, which is different from your intake. In such a short time, the weight will definitely drop. If you return to a normal diet in the later stage, your weight will definitely rebound, because in the process of milkshake, your metabolism will decrease and your nutrient intake will be incomplete, which is very harmful to your health. So if you lose weight, you should supplement your diet properly.