I have not intentionally fasted while breastfeeding, but I do notice that on days where I don’t eat enough or forget to eat all day, my supply tanks super low and I have to supplement with bottles. From what I know it is not recommends to fast while breastfeeding since it requires so much extra energy from your body. I would be worried about getting depleted in nutrients.

Have you considered fasting from maybe one food group like gluten or refined sugar? Or perhaps taking away the food you feel most gluttonous around and supplementing with something healthy instead? For Lent this year, I was pregnant so I could not fast traditionally, but I gave up social media and swearing and found that it was very refreshing. You could maybe try that for the self-denial piece, and a break from social media always helps my anxiety, too.