Very-low-calorie diet

A very-low-calorie diet (VLCD), also known as semistarvation diet and crash diet, is a type of diet with very or extremely low daily food energy consumption. VLCDs are defined as a diet of per day or less. Modern medically supervised VLCDs use total meal replacements, with regulated formulations in Europe and Canada which contain the recommended daily requirements for vitamins, minerals, trace elements, fatty acids, protein and electrolyte balance. Carbohydrates may be entirely absent, or substituted for a portion of the protein; this choice has important metabolic effects. Medically supervised VLCDs have specific therapeutic applications for rapid weight loss, such as in morbid obesity or before a bariatric surgery, using formulated, nutritionally complete liquid meals containing 800 kilocalories or less per day for a maximum of 12 weeks. Unmonitored VLCDs with insufficient or unbalanced nutrients can cause sudden death by cardiac arrest either by starvation or during refeeding. Very-low-calorie diets (VLCDs) are diets of or less energy intake per day, whereas low-calorie diets are between 1000-1200 kcal per day. The routine use of VLCDs is not recommended due to safety concerns, but this approach can be used under medical supervision if there is a clinical rationale for rapid weight loss in obese individuals, as part of a "multi-component weight management strategy" with continuous support and for a maximum of 12 weeks, according to the NICE 2014 guidelines. The US dietary guidelines recommend that VLCDs can be used for weight loss in obese individuals only in limited circumstances and only under supervision by experienced personnel in a medical care setting where the individual can be medically monitored and high-intensity lifestyle intervention can be provided. For the general public, VLCDs are not recommended due to low evidence. As there are considerable risks of starvation with an inadequately composed or supervised VLCD, people attempting these diets must be monitored closely by a physician to prevent complications.