This is my 2nd time trying to fast, the first one was a few years ago and I was able to make it to the 3rd day, just tried fasting yesterday and the headache was killing me so I had to break it. I suppose this is a side effect of electrolytes but all I have at my home is normal salt. I’m a really sedentary person that rarely even get sun or exercise, would fasting be dangerous for me? Also, next time I try to fast and get a headache I’ll probably try take some meds.
At the very least getting electrolytes for fasting would be incredibly important. I’m unsure if what you’re dealing with would be a side effect of no electrolytes or not. But I’d start with that. Also, try the first week or so doing only 16/8 intermittent fasting so your body adjusts to it. If you can, try keeping what you eat keto/low carb. It’ll help your body adjust.
Easing yourself in seems to be the standard advice. Start at 12/12 for a week or so and then increase your fasting window an hour or two per week to give your body time to adjust.
I can’t speak to the safety of doing fasting while sedentary. But I can tell you getting some movement on really helps pass the time, for me at least.
As for electrolytes, it’s true they make longer fasts much easier, but under 16 hours I’d be surprised if that’s the issue. What’s your water intake like? What are your caffeine habits and do they change on fast days? How are you handling mental stress during your fasts? I started getting brutal headaches during my second week of OMAD, turns out I had been grinding my teeth. Fasting can trigger the release of adrenaline, and how your body deals with that hormone can have a huge affect on how you feel during fasts.