Well, what, woke up today with the idea that you urgently need to get rid of all excess weight , without the slightest mercy and indulgence? Curiously, what led to such conclusions. Presumably, you either realized that everything in your life still did not go as it should, and with enlightenment came the thirst to fix everything in the shortest time, or you just remembered that in a month, not later, you need to look at all 100 (not kg, but millions). Whatever it was - it's your own business. Well, our duty is to curb your laudable impulse and to explain very clearly that to lose 20 kg in 20 days, the task, if real, is not at all safe.
Size matters
Yes, it's your size. Let's see what the diet means, in which they lose 20 kg in 20 days. If your weight is 70 kg, and you want - 50, this is one thing, and if your weight is 150 and after the diet is 130 kg - this is quite another matter. Remember, for a month the maximum permissible weight loss is 10% of the initial mass, that is, 20 kg for people with different weights - this can be fatal, and maybe not tangible.
Metabolism
When you sit on a diet, whether it's a diet of 20 days minus 20 kg or an ordinary 3-4-day diet, the body experiences stress. Due to this condition, in the first days, you lose all the excess fluid and lose weight. Further safety depends on the duration of stress.
After several days of weight loss on a diet, the body understands that something has changed and for safety it is worth putting aside for the already come "black" day. Fat deposits begin to form actively, even from the meager food that you consume on a diet. A metabolism , that is - spending on life, building new cells, regenerating tissues, moisturizing the skin, all these things are secondary, they, like mice, can be saved. As a result, you lose muscle mass, gaining the same "fat", your hair, nails, teeth and bones become vulnerable and brittle. All nutrients are spent on the most important - the heart, brain, blood and fat deposits in case of already onset of hunger. Establish metabolism in the future, even with normal nutrition, is not always possible.
Appearance
Well, oh well, if you are not heavily occupied by what is inside, then maybe you will somehow react to the following. Imagine, what will you look like if you drop 20 kg in a week? Sumptuously? And if you think better? The fact is that with such rapid weight loss, the skin does not have time to contract after new forms. As a result, the inevitable "companion" of a fast diet are stretch marks, which get rid of even heavier than from cellulite.
You have only one way out: stop treating your body as a servant. It is not created to satisfy you with its appearance, it is not in order to be experimented with over it. Respect yourself and value your health!