Well...I know this is an ancient thread but this just happened to me! I was in ketosis (after 2 days on the fat fast...no recommended here I KNOW...but it works for me) --> and then my dad came over with a cake he made. A kind of sponge/cookie/icing thing. I had two pieces!
I then went for a 1hr run, and 1hr body pump session about 2 hours after eating the cake.
I tested myself now (6hours or so later) --> and I'm STILL in ketosis [albeit mild].

Very odd. Good....but odd. Is it possible it was due to the exercise? That the insulin surge didn't kick in? Or will I perhaps get bumped out by tomorrow morning?

A tad confused.