I use Keto-Diastix when I'm fasting. It tells me when I've gone into ketosis, and how far I've gone. It's a little stick you pee on that changes color depending on how many ketones
are in the pee. I've noticed that I don't like how it feels to be in
deep ketosis, so I often suck on a mint or drink a little juice to raise
it slightly — to stay in ketosis but not too deeply. I like to stay
around moderate or a little more (as it shows in the picture).
I also occasionally, when it feels right, have a little chicken broth. Probably average one cup of broth a day, but I don't stick to any regimen about it, unless I'm doing an experiment, like when I wanted to find out what happens after the third day of a water-only fast (read about that here).
This morning, the sixth day of a fast, my hip hurt and I felt generally yucky. But I didn't want to break my fast yet, so I compromised and had about an ounce of cooked hamburger meat (about the size of my little finger) and a single cooked Brussels sprout, and a piece of lettuce. After awhile I felt fine. Apparently that's all I needed. It is now ten hours later and I still feel fine, haven't had anything else to eat, and am still in ketosis.
The point of this is that you don't need to think in terms of absolutes. It doesn't have to be all-or-nothing. Fasting can be relatively pleasant, and you don't need to be hardcore about it. If you go for awhile without food, that's good. If you have a little something and then go even longer, that's even better (until your fast turns into starvation, which you should avoid).
Adam Khan is the author of Principles For Personal Growth, Slotralogy, Antivirus For Your Mind, and co-author with Klassy Evans of How to Change the Way You Look at Things (in Plain English). Follow his podcast, The Adam Bomb.