The sustainability of using extended fasts past 48 hours is in proportion to how much extra body fat you have. The more fat you have, the longer you can fast and the less you have to eat. As you approach say, 10% or less body fat for males, your eating frequency has to go up because your body needs energy from exogenous sources. But one meal a day (omad, fasting for 22-24 hours a day) is infinitely sustainable.

Last year I lost 20 lbs a month for 5 months, and I could have lost it even quicker because I was eating a lot more frequently than my above example.

People have lost 60 pounds in a month, 100 in 2 months on the snake diet. The only plateaus you hit fasting is when your body is holding onto water. If you’re in ketosis and not eating, as long as you have the fat stores, your body is burning almost pure fat.