I've recently adopted a 16/8 approach and I'm wondering whether during those 16 hours the teaspoonful of fish oil I take with my vitamins or the 2 cups of decaf coffee I drink with cream in the morning are eliminating or even reducing the benefits I hope to derive?
I would not say that I am an "expert", but in the past two months I have found success in implementing a daily IF (8/16) and have achieved much better results than paleo or primal on their own.
I do not count coffee with a tbsp of coconut oil or butter, fish oil, fasted pre workout BCAAs (10-15gms) or my 2 daily Brazil nuts into the "feeding window" and only consider my first real meal as the official start. I do tend to eat my second meal about 4 or 5 hours later, so sometimes the coffee/supplements/etc. do fall into the 8 hour period, but more often than not they don't.
My abs are visible for the first time in a while and my strength and muscularity have been maintained unlike what happened when I followed a strict Loren Cordain style paleo. That time, I got abs, but I also looked rather skinny and emaciated.