Keto and the Menstrual Cycle: Pros and Cons

You might have heard that going Keto can disrupt a woman’s menstrual cycle. Is it true?

For some women, yes. Although there’s only a tad of science suggesting Keto leads to irregularity or missed periods (amenorrhea)[*], there’s more than a tad of anecdotal reports.  

Anecdotal data is data too. We should take it seriously, and later we’ll review possible ways that a Keto diet might interfere with menstruation. 

But the data goes both ways. There’s also data—both anecdotal and peer-reviewed—suggesting Keto can improve a woman’s reproductive health.[*][*] 

You’ll learn both sides today, along with practical tips for maintaining a healthy cycle on a low-carb diet. First, though, let’s cover some basics. 

What Is a Healthy Menstrual Cycle?

Every month or so, women of reproductive age go through a biological process to prepare for a possible pregnancy. This process—which involves the fluctuation of sex hormones, the release of an egg from the ovaries (ovulation), and the shedding of the uterine lining (menses)— is called the menstrual cycle.[*] 

Most women start cycling between the ages of 10-16 and stop cycling at menopause in their late 40s or early 50s. The average length of the menstrual cycle is 28 days, but this figure can vary considerably from month to month and from woman to woman.[*] 

A healthy menstrual cycle is largely dependent on the healthy activity of a slew of female sex hormones. These hormones include follicle-stimulating hormone (FSH), luteinizing hormone (LH), oestradiol (a form of estrogen), and progesterone. 

Without going too deep (this isn’t your freshman physiology textbook), let’s see how these hormones behave during a healthy cycle.  

Before ovulation (the follicular phase), FSH, LH, and estrogen should be high. After the egg is released (the luteal phase), estrogen falls and progesterone rises. Finally, assuming the egg is not fertilized by a sperm cell, menstruation occurs, and the cycle begins anew.[*] 

But it’s not just sex hormones influencing a woman’s cycle. Both insulin and thyroid hormones are linked to reproductive health as well.[*][*] And that’s where this story links up with the Keto diet.  

Can Keto Have a Positive Effect on the Menstrual Cycle?

The menstrual cycle is a complex hormonal dance. Dietary change only adds to this complexity. 

One way that low-carb diets may positively affect this system is by improving insulin function. When someone is insulin resistant (a hallmark of type 2 diabetes), they can’t properly regulate blood sugar and end up storing excess body fat.[*]

How does this connect to the menstrual cycle? Well, insulin resistance is also linked to polycystic ovary syndrome (PCOS), and PCOS is a primary cause of female infertility, menstrual irregularity, and missed periods.[*] 

Here’s the good news. Several studies suggest that low-carb diets may improve reproductive health in women with PCOS.[*]   

On top of that, a 2017 meta-analysis found low-carb diets to (generally) improve fertility outcomes in overweight and obese women.[*] Low-fat diets? Not so much.  

4 Ways Keto May Disrupt the Menstrual Cycle

Not all women have healthier menstrual cycles on Keto. Here are four potential reasons why the Keto diet and your period might not be a great fit. 

#1: Rapid weight loss

People tend to eat less food on Keto while simultaneously burning more calories.[*][*] That’s an effective combo for weight loss. 

Sometimes a little too effective. If fat loss happens too quickly, a woman’s estrogen levels will fall[*]. Low estrogen, unfortunately, can drive menstrual irregularities.  

#2: Stress

Stress is a well-documented disrupter of the menstrual cycle.[*] The stress hormone cortisol can bind to most cells in the human body, including cells that influence reproductive health. 

Dietary change can be difficult, and going Keto can be uniquely stressful. It’s hard to give up carbs. 

And if you’re dealing with Keto flu symptoms from carb withdrawal, that’s stressful too. Even if you know the symptoms are temporary. 

#3: Calorie restriction

Because Keto reduces hunger hormones, many people end up eating fewer calories overall.[*] Unfortunately, significant calorie restriction can interfere with the female reproductive cycle.[*] 

#4: Thyroid health

Too much calorie-cutting on Keto can also interfere with thyroid function. And disruptions in thyroid hormones are linked to disruptions in menstruation.[*]  

Thyroid hormones, however, aren’t just sensitive to calorie restriction, but also carb restriction. That’s why both T3 and T4 often decline on low-carb diets. 

It’s not clear, though, whether this decline is a cause for concern. In fact, low-carb diets may be therapeutic for certain thyroid disorders.[*] 

Tips to Maintain a Healthy Cycle

Maintaining a healthy cycle is a holistic endeavor. It means sleeping well, managing stress, and eating right. It means taking care of yourself, in other words. 

If you decide to experiment with Keto during your reproductive years, consider these additional tips:

Don’t skimp on calories

It’s easy to undereat on Keto, so be sure to throw enough energy down the hatch. To stay on top of this, track your food intake with the Carb Manager app and supplement with Keto-friendly snacks as needed. 

Be cautious with fasting

Intermittent fasting has benefits, but it also increases the odds of calorie restriction. If you are considering IF, start with a 12 or 13 hour overnight fast, work your way up slowly, and back off to a shorter fast if your periods get wonky. 

Eat nutritious foods

Hormonal health depends on what you eat, so eat nutrient-dense whole foods like vegetables, meat, fish, eggs, and nuts. These foods are rich in vitamins, minerals, and protein to support reproductive health. 

Allow time to adapt

When your diet changes, your hormones change. This is normal. 

Allow a couple of months for things to smooth out. If things are still bumpy then, mind the next two tips. 

Cycle your carbs  

Eating high-carb 1-2 days per week— a practice called “carb cycling”, “Keto cycling”, or “cyclical Keto”—may improve thyroid function and stabilize reproductive hormones. It hasn’t been tested in the lab, but it may be worth trying out. 

Don’t force Keto

Let’s say you’re doing everything right on Keto, but you’re still having issues. It’s time to try another menstruation diet plan.  

Keto works for many women, but if it’s not working for you, consider another whole foods approach like the Paleo or Mediterranean diet.  

It would be nice if one diet guaranteed perfect health for all humans, but that’s not how life works. You have to tinker, experiment, and recalibrate until you discover which diet works best for you. 

And when you do, all the tinkering will have been worth it.