Why Fasting Feels Different in Midlife Women

A 72-hour fast, an unexpected HRV signal, and what the science reveals about fasting in perimenopausal and menopausal women

Inside the Playbook: January Edition

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Most fasting research either excluded women entirely or didn't differentiate by hormonal stage. Which means when midlife women apply these protocols, we're working blind. I learned that the hard way at hour 53 of my last fast.

I have been doing 3–5 day water fasts twice a year for years and I know the rhythm. For me, it often starts with a slight discomfort as the body adjusts. By day two, the hunger is gone and replaced by a strange and uncanny clarity. Strength training still feels possible and even productive until somewhere around day four.

That rhythm has always been reliable… until this time. It was nothing dramatic but by somewhere around the second night my body stopped cooperating.

I first noticed it walking up a small incline. It felt heavier than it should. Small movements were demanding more effort than they had done in previous fasts. When my Garmin flashed an out-of-range health metric at 53 hours in, I realised this was physiological.

Here’s what I learned about fasting and the female midlife physiology.