JoAnn, I have no idea. I have been roughly at this same weight for a year now, and I would not be unhappy to lose another 10-15lbs. But this is not in my control so I have to forget about the weight and just enjoy my better health. I have not been on a scale for months and do not feel any worse for it, in fact I feel better not chasing a number anymore and just focusing on day to day energy and feeling good.
I do know that for a lot of ZIOH women, there does appear to be a time when the weight loss stops, but really, those women know there is no other 'way' for them to be eating. For them it is a matter of feeling well and carrying around a few extra pounds, or feeling poorly and gaining weight back.
Who knows where I (or them) will be a year or 2 or 10 from now though.
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Happy, the only time I have heard of people with that complaint, was when they were not eating enough fat. I heard of one woman complain of exactly what you are saying, and it turns out she was living pretty much off of beef jerky. She 'quit' ZC and when back to her LC/VLC and blamed ZC for making her feel poorly.
I am not saying that is you, I am only pointing out that not enough fat seems to bring on those exact symptoms you mentioned. When you went back to eating carbs, you were getting the energy you should have been getting from eating more fat. Protein does not provide a lot of energy on a ketogenic diet
Nothing scientific or groundbreaking here I am afraid, but that would be my very first guess.