Fast diets are popular because they offer significant weight loss in the matter of weeks, even days. This is because the intake of calories is set at the lowest possible level, which is usually done by reducing carbohydrates and fats in the menu. By doing this, the energy gained from food is not enough to satisfy the needs of the organism. In this case, the body needs some new energy sources and that is when glycogen is depleted. But, this is not enough and that is how fat burning process starts.
So, this means that as the intake of calories decreases, the fat burning process intensifies. This would make a fast diet a perfect diet except for a problem. Inducing the processes that create glucose from fat tissue might also create some side products that might be very harmful for the organism; the toxins that might even damage the brain. This is why all fast diets do not last longer than a couple of weeks; more than that might be dangerous. Also, continuing a fast diet more than recommended will simply exhaust the body and that really diminishes the effects of weight reduction.
Many fast diets are based on taking liquid meals, which contain a lot of vitamins and minerals but few carbohydrates and even less fats. One of those liquid diets that work is cayenne pepper diet, also known as lemon juice diet. Beside those two components, there is also maple syrup and water for mixing all of the elements. Another meal included in this diet is based on cleansing tea only. Cabbage soup diet can also be considered as a liquid diet. This soup is really very healthy, but it cannot replace the lack of carbs, so it should not last longer than two weeks. There are also very fast diets, which last for a couple of days only and allow the intake of liquids only with huge amount of vitamins and minerals and almost no carbs. Furthermore, fruit juices can be used in a liquid diet. This is a bit healthier option because some fruits contain certain amounts of glucose.