I'm not really trying to do it 'by the book' -- I think it's better that you come up with something that works for you.
Fasting with just water is a bit tough, as you can get a metallic taste in your mouth that is rather disagreeable. So that's my 'fix' for that problem.
1kg of fat would be 9000 kcal. Impressive energy expenditure there. Of course a lot of water weight is lost initially (when fasting or just skipping all carbs) but that rate won't hold for weeks on end.
I thought in ketosis it wasn't energy expenditure, the liver causes fat to break down and pass through your bladder? ... maybe I have that all back to front though :\ Maybe ketones pass through your bladder and they also break down fat cells...
In the absence of metabolic disease, the body breaks down fat to use the resulting energy. Think about it evolutionarily; "there's no food right now, time to jettison my energy stores"?
Ketosis is a pretty weird state brought on by lack of carbohydrates. The liver starts producing ketones, ketones rapidly breakdown fat cells to boost blood sugar.
It is mostly unrelated to diabetes as that relates to insulin response.
Ever been in the middle of a hard workout and noticed that you smell like ammonia? That smell means you are burning protein, probably from your muscles. I have only ever seen this during extended exercise, but the same thing during a fast would be a clear indicator you are burning muscle.
So that's what that is! I used to notice that a lot when I first started cycling aggressively in college. Once I got into better shape it mostly went away. Thanks for the tip.
I haven't noticed any muscle lost -- but then again I put on muscle /very/ easily (a bit too easily actually, I get hypertrophia if I do too much sport).
For energy, it turns out your body /does/ have some to burn, and once you made the switch to burning fat, well, usually there's a nice source of energy... I also wonder if you don't get a small dose of adrenalin in too, which would explain the 'high' you get after a couple of days.. but don't quote me on this..
But as I mentioned, the fruit juice input in the morning does help get the day started. Oh, and the coffee contains some nutrients too, so it's not like I'm totally starving.
As the previous poster replied, it's related to https://en.wikipedia.org/wiki/Ketosis
I don't know if you can really get rid of the taste, I'd be curious to know of course; but you kind of get used to it really.
I personally don't mind taking fruit juice, as it does give a small energy boost, especially in the morning.
Not everyone gets it. Fasting puts you in nutritional ketosis as does ketogenic / very-low-carb dieting. But the metallic taste is usually a temporary and harmless keto-adaptation symptom. The body's ketone production and consumption aren't fully balanced at first for quite a while, during which some people flush out most excess ketones in urine while others breathe out more of them. As you keto-adapt (takes from a week to a few months depending on individual), ketone bodies (a byproduct of fat oxidation) are fully utilized in place of glucose by more and more tissues/cells over time, until balance is achieved.
The metallic taste is excess ketones. If your body is not used to using ketones, some will be excreted in the urine and saliva.
If you really goose your ketogenic metabolism, your body gets better at using ketones and the taste will go away. You should also be sure to eat/drink extra salt during a fast or ketogenic diet due to water loss.
Fasting with just water is a bit tough, as you can get a metallic taste in your mouth that is rather disagreeable. So that's my 'fix' for that problem.