I have been told that hair loss increases when one doesn’t meet their caloric and nutritional requirements. does this happen when you fast ?
It has nothing to do with the kind of fasting we talk about here in IF. You still get all of your daily nutritional needs met during your eating window (eg eat healthy balanced food), and if you are going for weight loss, you are probably just in a mild overall calorie deficit, not starvation levels. If you are doing it for genera health purposes, then you are not at a caloric deficit.
Studies have found the link between vertex alopecia and metabolic syndrome. Applying the approach that fasting can only improve insulin resistance and metabolic syndrome - its longer term effect on hair can only be beneficial…
If there is any negative shorter term one - it could be related to the (lack of) quality of macro nutrients