The simple answer is yes, I was very tired at first. I had so many early nights in the first few weeks I thought I would never have any life again. I would be having a warm bath by 7pm and then very early to bed. But it passed - very quickly. I cant remember exactly how long it took but amazed myself that warm bath and early night was very quickly replaced by a walk in the park after an early morning swim and after a full day in work. My advice is to listen to your own body, it takes time to adjust to this diet and time for the energy to come flooding in. You have to detox from Carbs and other foods, that takes time. The headache is part of that. So drink more water - the universal cure, go to bed early, watch the weight drop off and wait for the tiredness to pass, it will. I hope this helps.
GSQ