Was completely wiped out those first two months, needed two to three hour naps daily just to function at all. The four months after that I've just dealt with unusual tiredness and low drive. Honestly been a genuinely tough half year, but worth it, I've lost 20 kilos and I'm at my target now. As nervous as I am about food thoughts creeping back, I'm planning to quit entirely a fortnight from now, once what I've got left runs dry, rather than switching to a smaller maintenance amount. Just can't sustain feeling like this indefinitely.
Do think my experience was atypical though, since exhaustion usually eases up for most people after roughly a month.