> Especially fasted cardio feels so good.

I noticed this too, if you mean the after effect. It almost got me a little worried though, since the good feeling is probably caused by a release of endorphins, which should usually get released as a response to pain. But I'm not sure.

Just to add, it is possible to gain weight while doing intermittent fasting. You just have to eat more :) Maybe add a meal so you don't eat 3x a day but 4x. The other tactics is to add 50g of some nuts to 2-3 meals a day, like walnuts, almonds, cashews...