Why fasting can affect women differently
Female reproductive physiology is sensitive to energy availability. The hypothalamic-pituitary-gonadal axis can interpret a large or sustained energy deficit as a stress signal, and prolonged or aggressive fasting may in some women contribute to menstrual irregularity or disruption. The hypothalamic-pituitary-adrenal (HPA) stress axis can also respond more readily, so what feels neutral for one person may feel taxing for another.
Much of the strongest mechanistic data comes from energy-deficiency states such as functional hypothalamic amenorrhea rather than from moderate time-restricted eating, so the picture is one of caution and individual variation rather than a uniform warning.
Gentler approaches that tend to suit women
Many practitioners suggest shorter fasting windows, such as 12 to 14 hours rather than very long fasts, and adjusting around the menstrual cycle, for instance easing restriction in the luteal phase when appetite and energy needs often rise. Adequate protein and overall calories matter, since the risk is tied to energy deficiency, not the clock alone.
This is general educational information, not medical advice. Women who are pregnant, breastfeeding, trying to conceive, or who notice cycle changes should consult a qualified professional before fasting.