If you start a diet, you may very well lose a kilo per day at the beginning.. Much of this weight loss, however, is not due to fat loss, but the excretion of water and an empty bowel. And after a few days of drastic fasting your weight loss is also due to the loss of muscle mass. In other words: the scale is misleading.
Why is this so? Because radical diets first reduce the amount of food consumed (relatively empty stomach and intestines) and then draw on carbohydrates. The body therefore uses its reserves of carbohydrates present in the liver and muscles, these being easily available. At the same time, the water which has bound glycogen (the storage form of carbohydrates in the body) is also eliminated from the body.
As a result, not only does the weight decrease somewhat, but the circumference of some parts of the body is also reduced, so that it seems that the fat pads have disappeared. Unfortunately, this is a mistake. As soon as you eat carbohydrates again, your stomach and intestines fill up and glycogen stores are replenished, which also helps to re-fix water. You have therefore regained weight.