Very low calorie diet (VLCD): The Very low calorie diet (VLCD) is a doctor-supervised weight loss plan that uses commercially prepared formulas (usually shakes and/or bars) to achieve significant short-term weight loss. The shakes or bars typically replace all food consumption for a period of weeks to months. Very low calorie diets generally contain about 800 calories per day, or even less, and are only recommended for use by moderately to severely obese persons under close medical supervision. The diet shakes and bars are designed to provide all essential vitamins and other nutrients. Sometimes very low calorie diets are prescribed that contain lean protein foods such as fish or chicken.
Very low calorie diets allow those who are moderately to extremely obese to lose an average of 3-5 pounds per week. This rapid weight loss can result in improvement of medical complications of obesity such as diabetes and high blood pressure. The rapid weight loss can also be a strong motivating factor for those wishing to lose a large amount of weight. Side effects of the diet can include fatigue, mild nausea, constipation, or diarrhea and dizziness.