Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life
Yeah, so for example 800kcal energy intake instead of 2000kcal could easily be construed as severe, and cannot be carried out indefinitely without the loss of the organism's life.
That doesn't apply because there isn't malnutrition.
There obviously is malnutrition in terms of macronutrients. That's the whole point of it, especially if the goal is to trigger autophagy. The organism is starved, so it breaks down its own tissue, so that it can later be rebuilt anew.
You are reducing the frequency of eating which the body copes very well with. The human body is designed to cope easily without food for a few days and if you have fat reserves its no problem. You are just bringing the body back to a more natural eating frequency intermittantly just so you lose a bit of weight etc.
Well, the body can cope, however, the way it does it has been determined by the evolution. If you put a contemporary Westerner in a time machine and drop them into the tundra 10,000 years ago, they would start "fasting" naturally straight away. Suppose they manage to acquire some food, they obviously are not going to waste it, so will eat as much as they can (which would usually not be a lot anyway). That's great, they would increase their chances of survival as a result.
If you subject the same person to fasting in the contemporary setting with abundant supply of food, when they come out of the fast they are likely to overeat and regain weight to compensate. Same mechanism, very different outcome due to the the environment change.
Ultimately you are a allowing a few additional processes to operate that are suppressed by eating frequently so a huge amount of health benefits before you even consider the health benefits of losing weight.
Well, the main process is actually called
starvation response.
If you take your definition of fasting being starvation then just about every creature on this planet is starving and facing starvation because natural wild animals tend to eat far less frequently than us especially carnivorous or omnivore animals. They use a bit of body fat, then they eat, then they eat again, then there might a gap where they consume their own body fat etc, that is the natural process.
That depends on the species and their environment, but yes - many have to go through periods of starvation, some don't survive.
You can find more information in the following book:
https://books.google.co.uk/books?id=yD02C44uIDUC&pg=PA15&redir_esc=y#v=onepage&q&f=false
As you can see right at the beginning, some researchers use the terms "starvation" and "fasting" interchangeably, some not. However, there is not a strict universally adopted rule on how to differentiate between the two.
I guess its a question of modern lifestyle vs our natural evolved biology does the modern lifestyle of easy food availability improve our health or hinder it. Is it ok to just remove the natural times where animals don't have access to food or does that improve our health by having frequent food with the body always digesting food. I would say the evidence is strong for some fasting being very beneficial and a great aid to weight loss naturally.
It's not even a question - there is overwhelming evidence of the currently prevailing Western lifestyle (particularly the fast food-based variety) being detrimental to health. Over 40% of Americans, the main authors of the Western lifestyle, are obese, something like 70% are overweight or worse. Britain looks only a little better.
Unfortunately, while there are some benefits of fasting in terms of cardiovascular health and potentially cell rejuvenation following starvation response (a lot of the research on that topic is based on indirect measures or animal studies), the research I have seen seems to suggest maintaining weight rapidly lost during a fast presents a considerable change. Anecdotally, I have observed this to be very much the case.
BTW I just spotted your post earlier. You reported losing 15kg in one month and hoping to lose a further 10kg per month. FYI The usually recommended safe and maintainable rate of weight loss is roughly up to about 2kg/month (0.5 kg/week).