Been fasting since March, Keto/LC since April. I found fasting easier before I went low carb but once I heard about feasting that helped so much. One thing, fasting resets my snacking, it curbs the impulse to grab something while passing through the kitchen, makes me more aware. A fat fast does not do that since I am still eating something.
I have done a few fasts with nothing but a little coffee HWC in the morning. It was ok. I never weigh myself during the fast, usually 36 hours after it is over, that way the water weight has some time. Usually I lose about 4 lbs or so on a regular 4 - 6 day fast. In July on a whim I did a fat fast after reading something by Dana Carpender and lost about 3 lbs or so. It was much easier and I was happier eating something than nothing. However you still have the hassle of preparing food and there is an element of something missing but that may be psychological. It seemed more effortless. Since then I went back to regular fasting, mostly shorter ones. Gearing up to do a longer one but cannot quite find the time. Plus I have to cook more since husband is on Keto but will not fast.
I ate small handfuls of macadamia nuts, a daily brazil nut for selenium, the occassional spoonful of EVCO, avocado and zoodles with lots of butter or cheese. I probably had an egg or two cooked in a lot of fat. I tried to keep my calories under 800 a day with most of those coming from fat. I do not eat pork and hate really fatty meat which is a problem
I have no idea when and if I lose fat or something else, except that in general whatever I weigh 36 hours after the fast is usually what I continue to weigh