In order to understand the dangers of fasting, it should be appreciated that when an individual fasts for an extended period of time, the body switches into dietary ketosis and in fact ketones can then be detected on the individual's breath. When in ketosis some individuals feel extremely alert and can endure long periods of activity. In dietary ketosis, whilst the muscles can burn fat, the brain however requires a continuing supply of glucose, although in prolonged ketosis the brain may begin to burn fat. Dietary ketosis must be clearly distinguished from diabetic aceto-ketosis which of course is a dangerous situation.

Dietary ketosis however is a normal response to fasting or restriction of carbohydrate intake. Since the brain requires a continuing supply of glucose, the body must generate this from its food stores. Although glucose is readily turned into fat, we cannot break fat down to maintain blood glucose levels. Instead the body breaks down protein to maintain blood sugar levels. However our metabolism does not distinguish between the muscles in the heart and in the limbs and in prolonged fasting there is significant muscle breakdown. This was the reason for the numerous deaths during the early days when Modifast was first introduced. In the initial clinical trials when the product was under evaluation, several women discovered that they lost their insatiable appetite and so dropped back to only a single Modifast meal (essentially a protein drink per day). These women then developed muscle breakdown and 49 women died of cardiac failure. This phenomenon of muscle breakdown in fasting explains the muscle loss in those with anorexia nervosa and bulimia. It also explains the weakness and fatigue these patients experience and also explains the tendency for them to put fat onto the abdomen when they do eat a meal; having lost muscle mass, when they do finally eat, the food is rapidly converted into fat. Tragically this physiological mechanism of muscle breakdown and storage of food as fat has been overlooked in the understanding and management of both anorexia and bulemia.


Of course the changes in fasting, anorexia nervosa and bulimia are far more complex than as outlined above and involve many other endocrine imbalances as a consequence of stress, lifestyle changes, drugs as well as diet. But the basic principle remains; namely:- cut back the calorie intake below a certain critical level and the body must maintain blood sugar levels by breaking down protein; this leads to progressive muscle weakness and can cause cardiomyopathy and heart failure.

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