I have been doing IF for 2 weeks and last night I slept for 2 hours before waking up fully, I laid in bed for the rest of the night, not able to fall back asleep until 30 minutes before my alarm went off.
Is this to be expected?
Are you also eating low carb? Poor sleep is a fairly well-documented side effect of that and I’ve definitely experienced it. What has really helped me is to eat carbs about an hour before I go to bed (I almost always eat oatmeal with some peanut butter and bananas in it). I shifted my eating window specifically to allow for that and now I sleep great. I also take L-Theanine and L-Ttyptophan at night and that helps me too.
Generally speaking though, IF and being on a caloric deficit can increase cortisol levels which affects sleep.