104. How Light Shapes Hormones with Sarah Kleiner

Mar 4, 2026

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Perimenopause can feel like your body is sending mixed signals. Appetite shifts. Sleep changes. Stress tolerance shrinks. And when labs come back “normal,” it can leave you feeling unheard in your own experience.

In this episode, I sit down with Sarah Kleiner to explore circadian rhythm as a foundational regulator of women’s hormones. We unpack leptin as a master safety signal that influences thyroid function, reproductive hormones, metabolism, and appetite. We also discuss how artificial light, screens, chronic stress, and restrictive dieting can blunt this signaling, especially in midlife when resilience narrows.

This conversation reframes hormone imbalance through the lens of rhythm and nervous system regulation rather than quick fixes. You’ll walk away with simple, practical ways to begin restoring amplitude to your day, starting with light, timing, and nourishment.

Sarah Kleiner is the founder of Sarah Kleiner Wellness and the creator of My Circadian App.

What's Discussed:

(00:00) Midlife as recalibration and why hormones reflect circadian rhythm and safety
(07:30) Leptin as a master signal and how it informs thyroid, metabolism, and fertility
(15:00) Cortisol, melatonin, and the hormonal cascade shaped by morning and evening light
(23:00) How artificial light, screens, and late eating disrupt hormone signaling
(31:00) Restrictive dieting, fasting, and why low leptin states keep women stuck
(39:00) Nervous system regulation and how chronic stress blunts metabolic communication
(47:00) Fertility, perimenopause, and why resilience narrows in midlife
(55:00) Practical circadian shifts for busy women and families
(1:03:00) Rhythm as root healing and returning to biological coherence

Thank You to Our Sponsors:

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Learn more about Sarah Kleiner:

Website: https://www.sarahkleinerwellness.com/

Instagram: @sarahkleinerwellness