Intermittent Fasting for Women: How It Affects Hormones

I believe that feeling our best comes when we learn to listen to our bodies—and one thing I’ve personally observed over the years is that I’m my most vibrant when I cycle in and out of intermittent fasting. When I’m consistent with a rhythm that works for me, I have steady energy, better digestion, and I find it easier to maintain my weight without stressing over every bite.

But here’s the key: I’m not rigid about a fasting schedule. If I wake up really hungry, I eat. If it’s the week before my period, I skip fasting entirely. Intermittent fasting, for me, is about listening to my body and tapping into that intuition—not “forcing” anything.

My current approach is mostly inspired by Dr. Mindy Pelz’s book, Fast Like a Girl. Her research is all about how women can fast in a way that supports our hormones, rather than working against them. I loosely sync my fasting habits with my menstrual cycle: during most of the month, I usually follow a 16:8 fast (an 8-hour eating window, so between 10 a.m. and 6 p.m., for example). During the luteal phase (the week before my period), I don’t fast at all. During my follicular phase, I like to experiment with a slightly longer fast, when my energy naturally feels higher.

This flexible approach has been such a game-changer for me. But it’s not just anecdotal experience—there’s real science behind why intermittent fasting can support women’s health, increase longevity, reduce inflammation, and bring a whole host of other health benefits.

To help us dig into the research, Lauren Zielinski, MSN, CNM, a certified nurse, midwife, and women’s health expert shares practical advice to approach intermittent fasting in a grounded, supportive way.

The Science Behind Intermittent Fasting

“There’s an abundance of research behind intermittent fasting,” Lauren shares. “And while it can lead to weight loss, the benefits run so much deeper. Research has shown its ability to “clean cells,” increase longevity, and decrease the risk of common diseases like diabetes and heart disease. Intermittent fasting keeps your DNA and cells healthy, and can slow down the aging process. I’d argue that it’s the closest thing to the fountain of youth.”

Lauren explains that intermittent fasting isn’t a fad—it’s been studied at leading research institutions including USC’s Longevity Institute and Harvard University. Studies link it to improved metabolic health, reduced inflammation, better brain function, and increased longevity.

How Fasting Actually Works in the Body

On a normal day, your body uses glucose from food for energy. But when you fast, it shifts from burning sugar to burning stored fat—a process called metabolic switching (a term coined by Johns Hopkins neuroscientist Mark Mattson, Ph.D.).

This switch doesn’t just help with fat loss. It triggers a cascade of cellular benefits. As fasting continues, glycogen stores deplete, and your body enters ketogenesis—releasing ketones into the bloodstream. These ketones:

• Enhance the body’s defenses against oxidative stress
• Help remove or repair damaged cells
• Improve blood sugar regulation
• Increase stress resistance and reduce inflammation

Even more fascinating: ketones stimulate the release of BDNF (brain-derived neurotrophic factor), a molecule that strengthens neurons and neural connections, supporting memory and cognitive health.

“Think of fasting as a mini ‘spring cleaning’ for your body,” Lauren says. “You’re giving your system a break from constant digestion, which allows your cells to repair and regenerate.”

The Unique Considerations of Intermittent Fasting for Women

While intermittent fasting can benefit nearly everyone, women’s hormones make it especially important to approach it with flexibility. Lauren emphasizes: “Women are not just smaller men. Our hormonal fluctuations throughout the month mean that fasting can feel amazing at certain times and depleting at others.”

Here’s a simplified guide based on what both research and many women (including myself) have experienced:

• Follicular phase (Day 1–14): Estrogen is rising, energy is higher. This is often the best time to try longer fasts (14–16 hours).
• Ovulation: Continue moderate fasting if it feels good, but listen to your body.
• Luteal phase (the week before your period): Cortisol is more sensitive, and your body may need more nourishment. This is a great time to ease off fasting or skip it altogether.
• Menstrual phase: Many women feel better with gentle fasting or none at all during their period.

This cyclical approach is what’s worked best for me. It’s also what Mindy Pelz and many hormone experts recommend: honor your cycle, rather than pushing through it.

The Long-Term Benefits of Intermittent Fasting

A 2019 New England Journal of Medicine review of fasting research found significant, wide-ranging benefits, including:

• Cognitive function: Improved memory and mental clarity
• Heart health: Better blood pressure, cholesterol, and resting heart rate
• Metabolic health: Improved insulin sensitivity and reduced risk of Type 2 diabetes
• Physical performance: Enhanced endurance and lean muscle preservation
• Longevity: Improved cellular repair mechanisms that may slow aging

For me, these benefits show up as sustained energy, better digestion, and feeling more in tune with my body’s cues.

How to Start Intermittent Fasting Gently

If you’d like to give fasting a try, here’s Lauren’s mindful approach:

1. Begin with 12 hours between dinner and breakfast.
2. After a week or two, extend to 14–16 hours if it feels good.
3. Stay hydrated—water, black coffee, and herbal teas are your best friends.
4. Focus on nutrient-dense foods during your eating window to support hormones and blood sugar balance.
5. Give your body 3–4 weeks to adapt. “It’s normal to feel tired or irritable at first,” Lauren says. “That usually passes as your metabolism adjusts.”

And perhaps most importantly: it doesn’t need to be all or nothing. If you wake up hungry, eat. If your body needs more fuel during certain phases of your cycle, listen.

When to Avoid Intermittent Fasting

While intermittent fasting can be beneficial, it’s not right for everyone. Lauren advises against fasting if you:

• Are under 18
• Are pregnant or breastfeeding
• Have a history of eating disorders
• Have diabetes or other blood sugar disorders

Always check with a healthcare provider before making major changes to your eating routine—especially if you have underlying conditions.

Food Freedom, Not Restriction

For me, intermittent fasting isn’t about restriction. It’s about finding a rhythm that supports my energy, mood, and hormones—and being flexible when my body needs something different.

Lauren sums it up perfectly:

“When done thoughtfully, intermittent fasting can be a powerful tool to support women’s health, but the key is flexibility. Our hormones are dynamic, and our approach to fasting should be, too.”

References & Sources:

• Pelz, M. Fast Like a Girl (2022)
• Mattson MP et al. “Intermittent Fasting and Human Metabolic Health.” New England Journal of Medicine, 2019.
• National Institute of Health. “Ketogenesis and Cellular Stress Response.”
• USC Longevity Institute; Harvard Medical School studies on metabolic switching.

This post was last updated on October 24, 2025, to include new insights.