well, I consistently powerfeed and have been doing so for almost 20 years.
my experience with it is this:
a fat fish after feeding is generally a healthy fish.
I believe that well fed fish are much more capable of fighting off diseases too.
pretty rare that a fish gets better when its not getting much food..
having said that, I feed a lot of high protein pellets/sticks etc and I do take the odd day off for my fish, in order to 'purge' their systems.
so I do powerfeed, but I guess I really do it 6 days a week with usually day off..as you can see from the growth of my barbs, they don't notice the missing day
some my fish will literally eat and eat and eat - not eating food that is in front of them is not an option..
I have a feeling that if you kept on feeding they would probably throw up = I have seen tinfoil barbs do this - they pack so much food down, and then they cough it back up, usually trying to eat it again LOL