Fasting almost never causes permanent weight lossicon, and it can be dangerous.
Fasting has been promoted as a way to cleanse the body of impurities and aid weight loss. But fasting almost never causes permanent weight loss, and it can be dangerous. The same is true for liquid diets.
Unsupervised fasting can upset the body’s chemistry and put an extra strain on the kidneys. During fasting extra water is excreted in the urine, causing temporary weight loss that is usually regained when the fast is over.
A second problem with any diet that severely restricts calories is that the body must use its own tissue for fuel. Because the body can convert muscle tissue into fuel more easily than it can convert fat tissue, the body draws on muscles and major organs such as the heart. Fasts and diets that claim to “burn” fat are actually burning needed muscle tissue.
At one time, high-protein liquid diets with as few as 400 calories per day were popular. These extreme diets had poor nutritional quality and were linked to several deaths from irregular heart rhythms and cardiac arrest.
Although high-protein over-the-counter liquid diets are now prohibited, some medically supervised liquid diets are used along with a behavior modification program. But even these diets do not have proven results after two to five years. Professionals warn that any diet of fewer than 800 calories a day is dangerous. Furthermore, starvation diets cause the body’s metabolism to slow down so that weight is gained more and more easily.
Another disadvantage to fasting and liquid diets is that they don’t provide for healthy eating habits once the diet is over. The only kind of weight-loss programs that really work are those that involve long-term and permanent changes in eating and exercise habits.