Non professional opinions of a 60kg guy who was full-time obsessed with learning nutrition/fasting for 2 months.
Literature on long term water fasts is severely lacking, most likely because it's not profitable to promote anti-consumption in consumption society. Reading medical studies directly is a great way to understand fasting and nutrition. With better understanding of nutrition it's much easier to see junk food for what it is. And in consequence it loses its appeal.
Prolonged water fast should not have negative impact on future metabolism. It is highly advisable to consult medical professional before and during prolonged fast. They can help monitor concentrations of vitamins, minerals and expelled protein. Unmonitored prolonged fast can cause deficiencies and those can cause severe medical problems. Non-adults, pregnant individuals or those suffering medical conditions that can be negatively affected should not attempt prolonged fast. Most common adverse effects include: bad breath, mood swings and deregulation of menstrual cycles. Anecdotal effect which seems more important than loss of fat is shift in worldview, proponents of prolonged fasting include Moses, Buddha, Jesus, Plato, Pythagoras and Gandhi.
After initial period during which body uses mostly stored carbohydrates and protein for energy, you can expect to lose 200g-300g of fat per day. To shorten the initial period, lower its adverse effects and "ease into" prolonged fast it is beneficial to eat only one heavy in fat meal per day for two weeks in advance.
Before the fast it's important to have adequate levels of sodium and potassium. They are expelled in normal quantities at the start of prolonged fast and it takes body some time to stop it. To mitigate effects similar to those of dehydration during first few days you can eat teaspoon of salt per day and progressively lower it. To mitigate hunger which will be most intense during first few days, you can "cheat" and drink tea or coffee (pure). After the initial period, hunger should subside, anecdotally it will return on its own after undetermined amount of time. When it returns it is very important to break the fast gradually. Start with something like a glass of broth, next day something equivalent to one egg, then two and four. Prolonged fasting can help reduce weight in long term, it can assist in changing eating habits. Best motivation to eat healthy is knowledge of nutrition, weight is just a byproduct of it.
Non professional opinions of a 60kg guy who was full-time obsessed with learning nutrition/fasting for 2 months.
Literature on long term water fasts is severely lacking, most likely because it's not profitable to promote anti-consumption in consumption society. Reading medical studies directly is a great way to understand fasting and nutrition. With better understanding of nutrition it's much easier to see junk food for what it is. And in consequence it loses its appeal.