Very low calorie diet
Very low calorie diet (VLCD) is a diet with very or extremely low calorie consumption per day. It is defined medically as a diet of 800 kilocalories per day or less. VLCDs are formulated, nutritionally complete, liquid meals containing 3350 kJ (800 kcal) or less per day. VLCDs also contain the recommended daily requirements for vitamins, minerals, trace elements, fatty acids and protein. The VLCD products are usually a powder which is mixed with water, juice or other low calorie liquid.
A VLCD diet is aimed primarily for severely or morbidly obese adults who must lose significant amounts of weight quickly, in order to live. It is also for those individuals who wish to lose some of their weight as rapidly as possible in a safe manner. Because of the extremely low calories per day, a VLCD diet cannot be used by children no matter how obese. The average weight loss on the VLCD program is in the range of 3 to 5 pounds per week, but it is to be remembered that at first you only lose excess liquid from your body.
A VLCD should never be undertaken without medical supervision.
Health benefits
A 1997 study concludes that the short-term use of a VLCD is very effective in rapidly improving glycaemic control and promoting substantial weight loss in obese patients with Type 2 diabetes. Moreover, a VLCD increases insulin sensitivity and reduces the substrate for gluconeogenesis. Thus VLCD treatment may improve glycaemic control more than calorie restriction alone.[1]
Adverse effects
The risk of gallbladder disease is greatly increased for individuals following a VLCD. [2]
A slowing of one's metabolism can occur as your body adapts so the brain and central nervous system, as well as other bodily systems, will cease to work efficiently.
The body will break down fat, but it will also break down muscle and other lean body tissue which can be very dangerous.
An imbalance in minerals and electrolytes can occur. Osteoporosis can be another danger, especially for women as can anaemia (a lack of iron in the blood). If taken to extremes, women can find that menstruation (periods) becomes irregular or stops altogether. A lack of serotonin in the brain can lead to clinical depression. The lack of essential nutrients on a very low calorie diet leads to a deterioration in the condition of hair and nails.
Another potential side effect is constipation (depends on the fibre content of the diet).[3]