I’m only doing IF weekends for maintenance but I’m the same, and if I need painkillers I need to eat, no buts. I leave oats soaking in the fridge overnight when I’m anticipating waking up in agony because they’re super easy to eat no matter what state I’m in. My take would be that anything you can eat to make it work is fine, but going for something with plenty of fibre or protein rather than something sugary or carby might fit closer to the spirit of intermittent fasting if you want to lean that way.
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Don’t worry about ‘undoing weeks of progress’ - calories have to come from somewhere. Worst case you might have a little more effort becoming reaccustomed to the IF schedule once you’re back on it strictly, but as long as you keep your commitment to fast on days you don’t need painkillers it should be very doable.