I've been doing 16:8 for about a week and a half now, religiously every day (not even having a splash of milk in tea during the fasting hours), weekends included, and I've lost nada. Not a thing. Not even 0.1 of a kg!
I have been stuck at this weight since the beginning of March, through 5:2, and now switching to 16:8.
I'm a healthy BMI, but put on a few kilos last year.
I'm trying to lose a further 4kg to get down to a weight that I feel good at, and look better at. It's not much, but I have completely stalled on the weight loss front since March, and I can't really understand it.
I know it's always hard to lose the last weight, but I can see on my body lots of places it could quite happily go from! 
Frustrating, but I will continue.