It’s very common as it affects other hormones in your body. That’s why there’s a ton of research stating fasting is not a good weight loss method for women

I started doing the 16/8 IF and my period was 12 days late this time. My cycles are like clockwork, between 24-27 days usually. I googled and this has been mentioned as a side effect. I can't get pregnant so I'm not worried about that and plan to continue the 16/8 and see if things stabilize.

Somewhat related. I do the 8 hr window for fasting. I had lots of break through bleeding from fibroids and very heavy periods. Both mostly stopped about 2 months into IF due to the effect on hormones.

It happened to me but here is more information:
https://www.precisionnutrition.com/intermittent-fasting-women

If your body is “stressed” your periods can definitely be thrown off. For your body, IF might be stressful. You can also stop menstruating if you are too thin. I’m assuming you’re at a normal weight and not underweight so that’s likely not it. Pregnancy is certainly a likely possibility depending on age but I’m sure you’ve ruled that out. I would see your doctor if this continues just to rule out a medical condition.

Are you pregnant?

Has anyone noticed disruption in their cycle as a result of intermittent fasting? I have been doing a 24-hour fast twice a week (not consecutive days) since June. It hasn't been too difficult and I like the structure of it. I had two regular cycles (June and July) but now it is August and my period has not arrived (after 6 weeks), which is not my norm - my regular cycle is 24 days. For reference, I am normal body weight/ BMI. I am not doing this for weight loss, but rather for maintenance and also for the other health benefits of fasting, such as reducing inflammation, etc. I would rather not stop the fasting routine if there was a likely change my body would get "back on track" before too long.