Absolutely... ref your weekend - NO criticism intended, because you're a big girl and you know what you're doing, but I was doing that a lot this year. The odd meal/day/weekend (even WEEK in May) off... and putting on so much weight in May, and seeing that even size 16s I bought just to tide me through were too small, has clicked something back into place in my brain - like in 2002... (The 14s I bought in May are now big... but the 12s I already had are small - so obviously some sizing issues going on there.)
Somehow, sticking to it is easier without the interruptions. For me at least. I will come out of ketosis mid-July (maybe even end June), because I need to eat fruit and live in the real (food) world a little more, but I'll always I'm sure use Dukan to get the "control" back... when (or if?!) I slip up!