Could be that your body is healing itself from previous problems? Have you been calorie restricting in the past? I have read many times that women have a harder time losing than men due to multiple hormonal issues as well as having more things to heal before the weight loss starts. You could take a look at
www.ketogenicforums.com lots of advice there about people new to keto not losing immediately. The usual advice seems to be keep calm and keto on it will happen when your body is ready (as well as people asking "are you eating enough?")
Edit to add to answer your initial question...I do quite a lot of fasting and have kick started weight loss through various types.. no food fasts, egg fasts and a week of bacon only.