Ultimate Guide To Intermittent Fasting For Women

Around the world, both men and women have succeeded with intermittent fasting (IF). Both genders have experienced health benefits like weight loss, blood sugar improvements, and reduced cravings. 

But should women approach fasting differently than men?

In some cases, yes. But it depends on the situation and person in question.

This article is a guide to intermittent fasting for women, but men will find plenty of helpful info here too. 

What Is Intermittent Fasting?

Intermittent fasting is the practice of taking regular breaks from calories. Depending on the protocol, these breaks can span anywhere from 12 to 36 hours. 

From an evolutionary perspective, intermittent fasting is nothing new. Fasting helped our ancestors stay lean and metabolically flexible while they survived the harsh realities of Paleolithic life. 

When a hunt-and-gather session came up empty, early humans fasted. Simple as that. 

During these intermittent fasts, our ancestors entered a fat-burning state called ketosis. And in ketosis, they accessed stored body fat for energy. 

We still have that program today. When we fast, blood sugar and insulin levels fall, and we burn body fat as fuel.

Is Fasting Different for Women?

Both men and women have been fasting successfully since prehistoric times. Both genders have the same basic machinery to access stored body fat and make ketones to fuel the brain during times of scarcity. 

Women, however, should pay special attention to reproductive health while fasting. 

There isn’t much evidence that fasting impairs fertility in humans—(there is some in mice[*])—but we know that calorie restriction, nutrient deficiencies, and rapid weight loss can cause irregular periods and disrupt reproductive hormones.[*] If the fasting protocol is too aggressive, this could be an issue. 

Similarly, pregnant and nursing women should be careful with fasts longer than 12 or 13 hours. The potential for nutrient deficiency is too high.  

Intermittent Fasting Benefits

When you practice intermittent fasting, you shift your metabolism towards burning fat. This may have beneficial consequences for both men and women:

#1: Weight loss

Multiple studies have found that intermittent fasting may be effective for weight loss in both sexes.[*][*][*]  

Why? Because when you compress your feeding window, you eat fewer calories overall. Fewer snacks, less weight gain.  

#2: Blood sugar control

Nothing keeps blood sugar low like eating nothing. Because of this, fasting may be a promising therapy for type 2 diabetes.[*] 

One study, however, found that three weeks of alternate day fasting (36-hour fasts) negatively impacted blood sugar control in nonobese women.[*] Meanwhile, the nonobese men in the study benefited.  

#3: Heart health

Intermittent fasting may improve heart disease risk factors like LDL cholesterol, triglycerides, and blood pressure in both men and women.[*][*] Plus, any intervention that reverses obesity makes the heart happy. 

More research is needed, however, since results have been inconsistent across studies.[*]  

#4: Other fasting benefits

Here’s a rundown of other gender-blind fasting benefits: 

• Longevity: Fasting activates an anti-aging cellular recycling program called autophagy.[*] 
• Brain health: When you fast, you burn fat and make ketones that fuel the brain with clean, efficient energy. 
• Lower inflammation: Fasting has been shown to reduce markers of chronic inflammation, the unnecessary immune activity linked to most modern diseases.[*] 
• Potential cancer therapy: Clinical trials are underway to test if fasting improves the efficacy of cancer treatment.[*] 

Risks of Fasting and Who Shouldn’t Fast

Different people respond to intermittent fasting differently. General risks include:

• Unpleasant hunger (some hunger is normal, but it shouldn’t be excruciating)
• Headaches
• Low energy
• Irritability
• Reduced focus
• Fantasizing about double cheeseburgers 

These side effects are often temporary as the body adapts to using fat for energy. 

Intermittent fasting is likely safe for most people, but the following groups should avoid it:

• Pregnant and nursing women
• Those with a history of eating disorders
• Underweight people
• Women with fertility problems

Finally, though fasting may be therapeutic for diabetes, medical supervision is essential to prevent dangerous hypoglycemia (low blood sugar) from developing. 

What to Eat During Feeding Periods

The goal when feeding is to eat the most nutritious foods possible. This means choosing whole foods like meat, fish, vegetables, fruits, and nuts over refined foods like cereal, pasta, crackers, soda, Twinkies, and anything else that comes in a package. 

Don’t skimp on protein during meals. Getting enough protein (at least 100 grams per day for most people) will help you retain muscle mass while intermittent fasting. To maintain muscle, be sure to strength train too. 

You might also consider a Keto diet to hasten your fat adaptation. When your body becomes accustomed to carb deprivation, fasting gets easier.  

For women especially, it’s important to eat enough calories. Under-doing the calories can lead to hormonal imbalances, missed periods, a reduction in thyroid hormones, and other potentially negative consequences.[*] 

A good rule of thumb? Don’t stuff yourself during feeding windows, but eat your fill.  

Drinks and Supplements While Fasting 

All non-caloric beverages—coffee, tea, bone broth, lemon water, etc.—are fair game during a fast. These drinks curb hunger and occupy the taste buds while you tick down the seconds to mealtime. 

Since they don’t contain calories, vitamins and minerals won’t meaningfully disrupt your fast—so feel free to supplement. Pay special attention to electrolytes like sodium and potassium because you excrete these minerals at higher rates during a fast.[*] 

Picking a Fasting Schedule for Women

When deciding on your ideal fasting schedule, here are your basic options:

• 12/12 or overnight fasting. Example: End dinner at 8 PM, start breakfast at 8 AM. 
• 16/8 or Leangains. Example: End dinner at 8 PM, have your next bite at noon.
• OMAD (One meal a day). Example: Eat all your calories in one sitting, preferably while the sun is shining to support restful sleep. 
• 5:2. Example: Fast Tuesday and Friday every week, eat normally the other 5 days. 
• ADF (Alternate day fasting). Fast every other day. 

Longer fasts, as you might imagine, carry a greater risk of severe calorie restriction. Because of this, women should start with shorter fasts (like 12/12) and work their way up slowly. 

Women should be especially careful with longer regimens like ADF. As a form of calorie restriction, ADF could impair fertility. Plus, it may impair the female glucose regulation system.[*] 

This doesn’t mean some women won’t thrive on longer fasts, but most women will likely do better on shorter programs. Compared to men, there seem to be more negative consequences when women restrict calories. 

If you’re a woman experimenting with intermittent fasting, make it a thorough experiment. 

Pay attention to your energy levels, mood, sleep, and other subjective metrics—and work with a doctor to monitor any relevant bloodwork. 

Maybe a 12 hour fast is your sweet spot. Maybe 14. Maybe 16. Tinker around and find what works best for you. 

And remember, it’s not a competition to see how long you can fast. It’s an exploration to optimize your wellbeing.  

Finally, check out the Carb Manager app for easy IF tracking and a custom intermittent fasting program. It has everything you need to succeed on your fasting journey, and it’s there for you whenever you’re ready.