Dietary treatment of obesity can vary between total starvation to diets which are only slightly hy-pocaloric. The most extreme form of diet is total starvation which means that no energy is given, whereas losses of water, electrolytes, vitamins and trace elements are compensated. Starvation obviously results in fast initial weight loss but requires medical supervision. Lethal complications have been described, probably because of cardiac arrhythmias (25). Starvation has the disadvantage of leading to considerable loss of lean body mass. Since most of the combustion takes place in such tissues, an increased breakdown of muscle in particular will result in a disproportionate reduction of the basic metabolic rate.
Most studies demonstrate that the long-term results of starvation programmes are not satisfactory. Rebound generally occurs and sustained weight loss is rare (26). An often held argument that starvation 'cleans the body' is not scientifically supported.
Modern VLCD products are composed of high quality proteins with adequate addition of electrolytes, vitamins and trace elements (27). Previously, the VLCDs were considered dangerous, an opinion that to a great extent seems to be based on the results of early treatment with the so-called liquid protein diet (28), an incomplete VLCD preparation, which resulted in several deaths. Today there is agreement that VLCDs can be used without medical supervision for 2 weeks and under medical supervision generally up to 26 weeks. However, almost continuous VLCD treatment for up to one year without serious side-effects has been reported (29).
Most VLCD products contain 400-800 kcal per day. During treatment with VLCD ketonaemia develops within a few days. Generally an anorectic effect is observed, and most patients on VLCD
programmes do not complain of hunger as long as they adhere to the diet. The advantage of the VLCD is that it safely makes it possible to avoid the food cues and the temptations associated with food cues. Many patients experience a euphoric sensation, at least during the initial phase of the treatment programme.
During VLCD the initial weight loss is several kilograms during the first week of treatmnt. The energy deficit results in initial breakdown of liver and muscle glycogen. Since glycogen in these stores binds its weight in water almost three times, there is an initial phase of diuresis explaining early losses. Towards the end of the first week the hypocaloric situation stabilizes and weight loss generally is about 2 kg/week, consisting of 60-70% of fat, the rest being lean body mass (30).
VLCD treatment may also be used in place of an ordinary meal. However, since most patients substitute the lunch meal, which often is not the most energy containing meal of the day, the effects of this strategy are generally modest. Probably, a dietary programme substituting dinner for VLCD would exhibit more marked long-term results.
VLCDs should not be used in patients with unstable metabolic conditions (such as renal or hepatic insufficiency), in patients with eating disorders, infections, or other acute catabolic conditions such as renal failure, severe liver disease etc. When VLCDs were introduced, several medical precautions were taken and patients kept under strict medical supervision. Later experience has demonstrated that after an initial metabolic screening, laboratory tests and safety control can be kept to a minimum.
Recently low calorie diets (LCD) have been introduced, generally consisting of 800-1200 kcal/day and based on the same components as VLCDs. Whereas these seem to result in safe weight losses, rather similar to those achieved with VLCDs, they may not induce ketonaemia and so may be more dificult to adhere to (31). Diets with an energy content in this range can also be composed of regular low caloric food products.
Vegetarian diets have often been promoted as healthy and suitable for weight reduction pro grammes. Several studies suggest that vegetarians weigh less and have fewer obesity-associated comorbidities. However, this may not only depend on the diet but could be explained by self-selection. Studies lasting for 1 year indicate that a lacto-veg-etarian diet, hypocaloric diet and a complete diet containing animal products with the same energy content results in the same weight loss (32).
Diet acceptance for long-term use is probably the most important component in making patients comply with dietary restrictions.
Numerous special diets are described in the literature, often marketed as 'different' or 'magic'. The principles are described by Summerbell in her review (6). As long as obese subjects attend to them and they result in energy deficiency, weight loss will follow. In reality few of them have been found to have any sustained effects on body weight and invariably the 'scientific advance' they are supposed to represent illustrates a commercial rather than scentific breakthrough.
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