Difference between starving and Ketosis

I’m always curious to learn about other people’s Fasting experiences so I watch lots of videos and sometime I come across vloggers doing all sort of Fasts. Mono-fruit fasts, bacon fast, juice fast and so on. One thing I don’t understand is why people do not research anything about health or how the body works before beginning these types of fasts. I mean, if you’re followed by a doctor or a clinic, that’s fine – I’m sure they’re professionals and they know what they are doing….well at least in most of the cases I guess. But if you’re fasting as DIY I would think that – considering the risks – the minimum would be to take a look at the side effects or any possible harm I can do to my body! Well it's not that obvious.
So now I want to talk about the substantial difference between Fasting and starving myself.
If I Water fast or Dry fast – as long as I have extra fat on my body – I won’t be starving myself, give that my body, after 2/3 days, will switch from burning sugar to burning fat – the magic of being into Ketosis!
Here - from this article - a clear explanation why burning fat and being into Ketosis will help me NOT being in starvation:
“Human fat is valued at 3,500 calories per pound. Each extra pound of fat will supply enough calories for one day of hard physical labor. Ten pounds of fat are equal to 35,000 calories! This is equivalent to 35 pounds of fish or 192 pounds of carrots, good value for your fat. We carry around a supermarket of reserves, capable of sustaining us for many weeks.”
On the other hand, if I’m “fasting” while basically doing an extreme caloric restricted diet – like mono-fruit juice fast, Master Fast System, or just simply mono-fruit eating diet – well then I’m not only depleting my body of all essential nutriments that I need but I’m not allowing myself to go into Ketosis (due to the high amount of sugar), so my body is still trying to run on glucose and not accessing directly to the fat storage that I have all over my body.
Those types of diets are harmful, would make me feel super weak, will eat all my muscle tissues, it cannot be sustained for long period of time.