What is ketosis? And how long can we stay in ketosis to lose weight without any health side effects?
Many of you know what ketosis is, without perhaps knowing the exact term: ketosis is in fact a state of metabolic alteration of fatty acids, which generally occurs on two occasions:
– after a prolonged fast (at least 2 days) , and in all those slimming practices in which fasting is proposed (assisted fasting, therapeutic fasting, etc.)

– in the diet without carbohydrates: for example in the most famous protein diets (the Dukan, the Atkins), and in the ketogenic diets (such as the Bulletproof diet: the latter are called LCHF diet, or diets low in carbohydrates and high in fat).

How ketosis occurs : our metabolism requires sugar from our body to carry out all activities, therefore carbohydrates; It is true that you can survive without carbohydrates, but this last resort does not make carbohydrates useless. It just says that in a world without carbohydrates, for example a post-apocalyptic world that I cannot imagine , a small group of human beings would be able to survive without carbohydrates. Not to live happily, fit and healthy. Surviving and living are not the same thing. Can you survive on bread and water? Yes, until serious nutritional deficiencies occur that make you sick. You can live with a balanced diet. Having said that, let’s say you love to survive, because you are training for the coming of the zombies or for masochism: and you have decided to give a clean cut to carbohydrates. If our metabolism works thanks to carbohydrates, the body will look for the sugars it cannot find in the diet.

On the other hand, our cells need carbohydrates and amino acids to feed themselves. The body looks for sugar : first there is a state of hypoglycemia, in which the reserves of sugar we can take are used (few by the liver, the rest by the muscles). In this way, weight loss occurs . Yes, because the lean mass is destroyed to obtain the glycogen (but the fat remains) and this obviously brings the scale down in a very short time. Next, the body tries to biosynthesize glucose from fatty acids (ketogenesis).
So you burn fat for energy. At the same time, they get rid of substances that are called ketone bodies. 
When these substances accumulate in the body it is called ketosis.