I hear from a lot of amazing women who practice intermittent fasting. This daily ritual is an important part of their health routine. These women fast to lose weight, boost productivity, support a ketogenic diet, or all of the above. It makes me beyond happy to see their successes. But like with most things, fasting isn’t for everybody, and I have concerns for women specifically.
Fasting can overstress your body, especially if you’re a woman of reproductive age. Many people think that pushing their fasts a bit longer is a good idea. Aren’t longer fasts more beneficial, Nicki?
Well, even assuming you do benefit from fasting, more of a good thing is not always better. Extended fasts often result in greater weight loss, but that weight loss isn’t always sustainable. Fasting comes with risks from consuming too few calories and nutrients. Women are highly sensitive to these risks.
The trick is to find a balance. That’s what I try to accomplish with my routine—I don’t eat around the clock, but I also allow myself enough eating time to get all my nutrients in. If I squashed my feeding window down to 4, 5, or 6 hours, I don’t think I could do that.
It comes down to balancing the risks and benefits. And in this article, I hope to help you—or any lovely women who benefit from fasting—find their balance.
Intermittent Fasting 101
We don’t need a fancy definition for intermittent fasting (IF). IF is just the practice of taking regular breaks from calories.
How long must these breaks be to qualify? That depends who you talk to, but somewhere around 12 hours is a good lower bound for IF, while the upper bound is around 36 hours.
When I say “breaks from calories”, I don’t necessarily mean zero-calorie breaks. Yes, some fasting regimens are noncaloric, but others allow limited calories on fasting days.
Anyways, the point of pausing the calories is to unlock some wonderful adaptations in the human body. When we fast, blood sugar and insulin levels drop, ketone levels rise, “longevity” pathways like AMPK switch on, and body fat burns preferentially.
Why do you think we haul around body fat anyway? It’s there for when the food runs out. Before the age of readily-available, calorically-dense food on every street corner, three meals a day plus snacks was a rare occurrence. Our ancestors survived these fasting periods by accessing stored body fat.
Now, if you plopped early humans into a Whole Foods, they wouldn’t burn much fat. Instead, they’d post up in the bulk goodies aisle (with those addictive banana chips) and add fat mass until a concerned employee called the police.
This is (more or less) what’s happening in modern society. Our genes still love to eat, but—for fortunate people like you and me—the food never runs out.
Practiced mindfully, intermittent fasting is a clever way to sync up with our ancestral roots. We aren’t meant to eat all the time, but as you will see, we are better served being conservative with fasting vs pushing the envelope.
Health Benefits of Intermittent Fasting
Before covering how intermittent fasting differs in women, I want to talk about the general benefits of intermittent fasting. These benefits apply to both sexes, but they’ll be bracketed by the risks and considerations sections that follow.
#1: Fat loss
Weight loss is why most women (most people, really) practice IF. IF promotes weight loss because:
- You generally eat less in a compressed feeding window.
- Fasting keeps insulin low—but from a purely weight loss perspective, this takes a 2nd seat to #1: reduced calorie intake. The reduced insulin levels can offer both benefits and pitfalls, so this is a tool we want to use wisely.
A lot of people view fasting as some sort of magic. But as research progresses, we can see that this tool primarily boils down to this: you tend to eat less if you fast for at least 12 hours daily. And if you want to lose weight, you need to operate at an (ideally mild) caloric deficit.
Low insulin helps because having too much insulin around blunts your ability to burn body fat and may contribute to disordered appetite control, which leads to overeating. Low insulin also signals your body to enter ketosis. Ketosis offers a good number of benefits for various situations, but its main benefit is likely improved appetite regulation.
#2: Ketosis
A bunch of fasting benefits can get lumped into the ketosis category. This fat-burning metabolic state—which you can enter via fasting, exercise, or a Keto diet—can help:
- Control cravings
- Stabilize energy
- Improve cognitive function
- Lower blood sugar and insulin levels
- Help manage type 2 diabetes
- (Potentially) treat chronic diseases like cancer and Alzheimer’s
- Lower inflammation
#3: Circadian rhythm enhancement
The more I learn about the circadian rhythm, the more I care about mine. The circadian rhythm is our 24-hour wake-sleep cycle that regulates sleep, body weight, mood, alertness, hormonal health, appetite, DNA repair, and pretty much everything we care about.
Since food sends “wake up” signals to your body, fasting overnight is crucial for restful sleep. That’s why fasting overnight makes sense for most people most of the time.
Fasting for Women: Special Considerations
Most fasting benefits aren’t sex-specific. Both men and women can burn fat, make ketones, and enhance sleep by not snacking overnight. But that doesn’t mean women don’t respond differently to fasting. In certain cases, we do.
My main concern is reproductive health. If a woman fasts too aggressively, there can be negative consequences for her fertility, menstrual cycle, and hormonal health.
A woman’s sexual health is highly sensitive to calorie restriction. By undereating, women of reproductive age can suffer irregular periods, low libido, missed periods (amenorrhea), and disruptions in hormones like estrogen and progesterone.
Also, rapid weight loss (common with longer fasts) has been shown to interfere with estrogen levels. That can interfere with your cycle too.
I also want to talk about pregnancy and breastfeeding. When I was pregnant with (and nursing) my two beautiful daughters, Zoe and Sagan, I was extremely mindful about getting enough calories—especially protein. I rarely went longer than 13 hours without eating and as much of that time as possible was spent sleeping!
Remember: when pregnant or nursing, you’re eating for two. We need more calories, not less. So, it’s fine to start working off some of that pregnancy weight, but it’s smart to play the long game rather than jump into a quick fix. Too much fasting or calorie restriction can tank milk production and set in motion some serious hormonal problems.
Once a woman goes through menopause (the cessation of her cycle), some of these concerns dissipate. But I still believe that all women should be careful with longer fasts. Menopause symptoms (and life in general) are stressful enough without the stress of serious calorie deprivation.
Who Shouldn’t Fast?
Fasting isn’t for everyone. Let me take a second to list the groups (both men and women) that should never go beyond a simple overnight fast.
“Never fast” groups include:
- Pregnant and nursing women
- Underweight people
- Those with a history of eating disorders
- Babies and children
And the “extra cautious” with fasting groups include:
- People fasting for diabetes or other chronic conditions (medical supervision required)
- Women of reproductive age
- Anyone who doesn’t feel right on a fasting regimen
The last point is important. Fasting is a stressful endeavor, and it might be too stressful for your body. If you’re feeling weak, low energy, or otherwise unpleasant, show yourself love and kindness by moving to an easier program.
Please, please remember this: Many people feel AMAZING for a week or two when fasting. Then, all sorts of problems emerge and energy levels tank. I’m talking about loss of normal hormone functions, disordered sleep, hair loss, and more. Unfortunately, when people hit this wall, they assume that they need to fast for even longer. More of what got us in a bad place is seldom a good solution. So, if you take nothing else from this article, please remember that any dietary change can be great for a time and then pose problems later. Be honest with yourself and adapt to what your body needs.
What To Eat To Support IF
The basic principle here is simple: Eat nutrient-dense whole foods at mealtimes. Fasting shrinks the window into which you must fit all your daily nutrients. You need to make that window count.
Protein is the nutrient I emphasize most for women. Inadequate protein is why many women suffer from body composition issues, lack of satiety, and weight loss issues—even when they’re doing everything else right.
If you aren’t eating between 0.8 and 1.0 grams of protein per pound of lean body mass (LBM) each day, you’re probably low on this macronutrient. Depending on your size, activity level, and body composition, this usually means getting at least 100 grams of protein per day.
But that’s the minimum. I recommend tracking your protein intake with an app like Cronometer, then making tweaks as needed.
What about micronutrients? Though it’s best to get most of your vitamins, minerals, and fatty acids from food, there’s a place for targeted supplementation. Three that come to mind are omega-3 fatty acids (EPA and DHA), vitamin D, and electrolytes.
Electrolytes are especially important for preventing fasting side effects like headaches, cramps, and fatigue. When you fast, you rapidly excrete electrolytes like sodium and potassium—and they need to be replaced. Might I humbly recommend some delicious, fasting-friendly LMNT for that purpose?
How to Choose a Fasting Protocol
If you’re familiar with intermittent fasting, you probably know the popular protocols. They include:
- 12/12 (overnight fasting)
- 16/8 (16 hours of daily fasting)
- OMAD (One meal a day)
- 5:2 (2 days per week of full or semi-fasting)
- ADF (alternate day fasting)
All these protocols have evidence behind them. I won’t be discussing their ins and outs today because my husband Robb already did that in this fabulous article.
What I will talk about is a basic strategy for approaching fasting. It’s not a complicated strategy. It’s also not a hard strategy to implement.
The first step is to start with the shortest fast on the menu: the 12-hour overnight fast. If you eat your last bite of the day at 8 PM, don’t eat your next bite until 8 AM the next morning.
Let the overnight fast become habitual. Let your body adapt to it and see how your sleep, weight, and mood respond. Once you’re comfortable with this routine, take stock of your situation. Do you think you could benefit from a slightly longer fast?
If so, lengthen your fasting window by hourly increments. Most women I talk to—including myself (yes, I talk to myself sometimes!)—settle somewhere between 13 and 16 hours of daily fasting. Anything longer and I just don’t feel my best.
Give it a try, be gentle with yourself, take into account any extraneous stressors, and things should go pretty smoothly. If you have a moment, I’d love to hear about your fasting journey—you can message us at @drinkLMNT on Instagram. We love hearing from you.
