I noted from your first post that you were fasting - I found it counter productive - in fact I need to space my meals out more to get the best results, eating earlier in the day with just a few carbs - none at all did not work either, so I have mushrooms or a tomato or some celery and cheese - I can eat bacon and eggs along with it, no problem, and my blood glucose level before dinner, last time I tested it, was 4.8mmol/l
As a last meal I can have a couple of different vegetables, or just one and then berries and cream.
It works well for me, and I find that my Atkins New Diet Revolution is a good guide as to what to eat and when - one of Dr A's guides was not to go more than 6 waking hours without eating.
I am really getting to the situation of thinking 'this is no big deal' and 'I can do this for ever' - plus I intend to knit myself a jersey with 'Dr Atkins was right' across the back - I might have to make it a bit loose to fit all the letters on.
There are various ways to low carb - rather than trying to stick to one which is not working for you do move things around to try to find what is going to be best for you.
Low energy might mean that you are eating too little, or at the wrong time for your lifestyle or metabolism.
I eat about 50, maybe 60 gm of carb in a day - most of them in the evening as that is when I am least insulin resistant. I concentrated only on my blood glucose levels to guide my eating - did not try to push them really low, just tried to keep under 8mmol/l after eating - that seemed to tip the balance - eating so as to spike and then waiting to get down to a low number again did not work for me.