Cyclic Fasting (my term) refers to not fasting at all for women a week before menses. The point of it is to maximize the body’s ability to make progesterone when it needs it most. 

Progesterone is a hormone that plays a crucial role in the menstrual cycle and pregnancy. It is primarily produced by the ovaries during the second half of the menstrual cycle, known as the luteal phase. Progesterone levels naturally fluctuate throughout the menstrual cycle, with higher levels during the luteal phase and lower levels during the follicular phase.

Avoiding a fast during the week that progesterone should be at its peak, could support the body’s ability to produce optimal levels of progesterone.