Keto is wack as shit lol, your body does not really want to use ketone bodies. That's why they're primarily produced under very physiologically stressful conditions (prolonged starvation, poorly treated type 1 diabetes, etc.). It's your body's last resort to get energy from somewhere. Don't push your body to that point.

I also think "calories in vs calories out" is another wack myth in nutrition/fitness that's constantly propagated. not all calories are the same. 30 calories of protein is different from 30 calories of complex carbs and your body deals with them in different ways. I don't trust anyone who tries to oversimplify metabolism

It is usually less healthy when you use any diet to reduce weight. Only when your body suffers from conditions that demand a diet it is helpful. Given that in western countries especially people are used to and it is a custom to basically have unhealthy eating habits, going back to a well balanced food is a good thing. But calling that a diet is wrong. Any extreme forms of diets that promote to normal people exaggerated intake of single forms of food are unhealthy after a short while. While there may exist medical conditions that require to do so for a limited time in a controlled way there can ony be damage be expected when doing so as a healthy person following the counsel of people who want to sell a cult or products.