I have done a couple of 48 hour fasts (although I do take milk in my coffee - sorry it is just too vile black) and I think these have given me a bit "extra" above my current normal. (Oh and I did one 68 hour fast but I won't do that again I think.
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But I've found the 48 hour fasts difficult to do, so now I just do 36 hour fasts which for me are much easier. For a 36 hour fast I eat dinner one night, go all next day on just drinks (inc milk in coffee, and some extra salt) then eat breakfast morning after.
I aim to do a couple of these a week, but that is variable to be honest. Some-times I just do the one meal a day thing, thus a 24 hour fast. I'm not very good on rigid routines, so it all gets mixed up a bit.
And yes I eat well in between the longer fasts. I generally aim for a low sugar diet, with not too many carbs. I don't avoid fatty foods, so I eat eggs, cheese, butter, bacon etc.
For whatever reason this just makes me feel less 'flu-ish - like it is helping to control something within my body. Perhaps that is just my experience, but for now it is making a difference for me, so I keep doing it.