Very low calorie diet

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A very low calorie diet (VLCD) provides less than 800 Calories per day. Some contain as little as 400 Calories. VLCDs were first introduced in the 1920s to replace fasting as a means of treating overweight people. Some take the form of a drink made from powder and water. So-called ‘liquid protein diets’ were freely available in the 1970s and gained considerable notoriety after they were linked to a number of deaths. It was discovered that the protein they contained was mainly collagen derived from cowhides. The diets were nutritionally inadequate. Deficiencies of certain essential amino acids and potassium were thought to have caused a loss of lean muscle mass, weakening of heart muscle, and heart irregularities which probably contributed to the death of at least 60 people in the United States. Such liquid protein diets are no longer generally available. Most modern VLCDs are designed to be nutritionally sound and provide the recommended daily intake of proteins, vitamins, and minerals to sustain health.

VLCDs can be dangerous if not used properly, or if taken by certain groups of people. Pregnant women and people with an eating disorder, psychiatric illness, a history of high blood pressure, diabetes, or heart, liver, kidney, or gall bladder disease, should not use a VLCD. Children, breast-feeding women, and the elderly should only take one if medically advised to do so. The general consensus is that VLCDs are safe if used under medical supervision and that they should be used only by those who are medically classified as obese (i.e. have a body mass index of at least 31). Many doctors believe they should be used only by the morbidly obese (BMI greater than 40). In Canada, laws ensure that VLCDs can be used only with a medical prescription; similar laws are being considered in the United States. Potential side-effects, even when VLCDs are used under medical supervision, include gastro-intestinal problems, fatigue, and muscle cramping. The risk of suffering side-effects is reduced by drinking plenty of fluids (at least eight glasses a day).

VLCDs have high rates of short-term success, with the majority of dieters losing 9 kg (about 20 lb). However, people usually stick to the diets only for a short time. They lose weight rapidly, but fail to maintain the loss. One British survey of VLCD users found that less than 20 per cent stayed with the diet for more than two weeks. The better VLCDs include regimes of exercise, nutrition education, and support groups to increase their long-term effectiveness.

VLCDs include the Cambridge Diet or Cambridge Health Plan, which has been used by more than 15 million people worldwide (see Cambridge diet).

A diet containing less than 800 kcal day⁻¹ specifically designed for the treatment of severe obesity. Usually, food substitution in the form of a drink made from powder and water is used. Ingredients in the powder are designed to provide nutrients in sufficient quantities to sustain health, and consist mainly of high quality protein such as egg whites, minerals, and vitamins. These diets require medical supervision and are not recommended for people with a body-mass index (BMI) of less than 30.

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