it’s just an adaptation period. Address the headache with paracetamol (or whatever you’re used to treating it with), address low energy with morning coffee. Preferably black but with a tbsp of heavy cream won’t hurt.
if you’re eating every day you don’t have to worry about electrolytes. Those are for the 3 day fasts and up.
Are you making sure to drink enough? I don’t think this timeframe should have such a noticable effect - I fast to maintain my weight, just at weekends (i.e. I do not have any excess weight to ‘back me up’) for a very slightly longer period than this (6 to 12) and never get headaches or exhaustion even after significant exercise or a solid morning of chores. I make sure to drink two \~500ml drinks across the morning, then another \~500ml drink with every meal and snack when I am eating. I’d be surprised if electrolytes were an issue on this timescale but perhaps if your diet is particularly lacking?
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Alternatively if you were accustomed to snacking late into the night beforehand this may have been more of a shock to the system and you may want to ease into it from a gentler split? But I would not accept these symptoms as ‘normal’.