Skip to content

Here's How The Keto Diet Can Mess With Your Period & Hormones

Tasha Metcalf
Author: Medical reviewer:
Updated on January 15, 2020
Tasha Metcalf
By Tasha Metcalf
mbg Contributor
Tasha Metcalf, based near Seattle, Washington, is the creator of Ketogasm, and author of the new book Keto: A Woman's Guide. Her Hello Keto course has had 58,000 students since its launch in 2017.
Sheeva Talebian, M.D.
Medical review by
Sheeva Talebian, M.D.
Reproductive Endocrinologist
Sheeva Talebian, M.D., is a board-certified reproductive endocrinologist. She graduated from Columbia University and obtained her medical degree from Mount Sinai School of Medicine.
Last updated on January 15, 2020
Our editors have independently chosen the products listed on this page. If you purchase something mentioned in this article, we may earn a small commission.
We know the keto diet affects men and women differently, and therefore, the approach should be adjusted accordingly. One of the things that can be affected by the keto diet is the menstrual cycle, and it helps to know what's happening during each phase. Tasha Metcalf, the founder of Ketogasm and author of the new book Keto: A Woman's Guide found the keto diet helped her reverse PCOS, boost fertility, and lose weight, and shares this journey along with tips for how to customize the keto diet to your needs. In this excerpt from her new book, she explains how the keto diet affects our hormones and how it may interact with each phase of the cycle. 
This ad is displayed using third party content and we do not control its accessibility features.

Diet and lifestyle can affect our hormones, which is excellent news once we know how to optimize this to our benefit. Eating a ketogenic diet can dramatically affect our hormones, so we need to do our part to ensure it is a positive shift and not one that throws us into hormonal chaos. Considering how a woman's body responds to a ketogenic diet, calorie restriction, and the oscillations brought on by each hormonal cycle allows us to implement the diet in a way that promotes the balance required to flourish. The goal is not to reach an ideal body composition at all costs but to lose excess body fat safely, without sacrificing hormonal health. A better body and happy hormones—you can have both!

How the keto diet may help balance hormones.

Besides clueing you in to overall health, is your menstrual cycle essential to pay attention to for any other reason? One hundred percent yes! Hormonal fluctuations related to your cycle play a significant role in your metabolism, insulin sensitivity, and food preferences—and, in turn, your ability to lose and store body fat.

The menstrual cycle also affects our sensitivity to the insulin hormone and, in turn, our insulin resistance. In the beginning half of the cycle, we are more sensitive to the effects of insulin and therefore able to take up glucose into the cells more effectively. This means that in the follicular phase, before ovulation, women are better able to efficiently metabolize carbohydrates for energy. One reason for this is that estrogen increases insulin sensitivity. If you are going to eat carbohydrates, the ideal time to do so is in the first phase of your menstrual cycle.

As progesterone levels rise and estrogen dips in the second phase of the cycle, we lose this sensitivity and become more insulin resistant. Insulin resistance impairs our ability to properly metabolize carbohydrates for energy, thereby increasing blood sugar, insulin levels, and fat storage during this time when a high-carbohydrate diet is consumed. Choosing low-carb foods is an effective way to bypass the impaired glucose uptake. Arguably one of the biggest benefits of a ketogenic diet is the alternative metabolic pathway to combat a faulty insulin response. Eating a keto diet during times of insulin resistance can help alleviate the effects of insulin resistance, balancing blood sugar and hormones.

This ad is displayed using third party content and we do not control its accessibility features.

When to start the keto diet in relation to your cycle

Keto is very beneficial during your luteal phase. Eating fewer carbs with higher protein and fat can help combat the increased insulin resistance in the second half of your cycle to balance blood sugar and hormones.

You can start keto whatever time suits you best, but consider starting your diet during the follicular phase of your cycle. After your menstrual bleed has ended and your estrogen is rising, you may have better compliance with your new dietary choices.

That's right: Impulsiveness can be affected by which part of the menstrual cycle you are in. Rising levels of estrogen in the follicular phase are related to decreased impulsive behavior compared to stages of the cycle when estrogen is low. As estrogen levels fall in the second phase of the cycle, impulsive behavior rises. This time also coincides with increased food cravings, which can further provoke impulsive eating behavior. Even with the best intentions, the combination of increased appetite, intense cravings, and impulsiveness can lead to excess intake and crush our efforts to even get started on a diet. Beginning your diet when estrogen levels are at their peak in the follicular phase of your cycle may help you battle the urge to quit your diet before you even get started.

Why your period may be wacky on keto.

If you start keto and then your periods go wild, what now? Relax! If you are using a ketogenic diet for weight loss, there are a couple of things happening concurrently. One, your calories have been reduced, which can trigger a stress response in your body. Be honest: Are you cutting your calories too low? Are you really eating as much as you think you are? Ketogenic diets are appetite-suppressing, which can be useful when trying to reduce calorie intake but can backfire if you aren't actually eating enough. Remember: The body sees undereating as a stressor; elevated cortisol will throttle your progesterone levels, and a missed period is a red flag to evaluate and adjust your calorie intake.

Another reason you could be experiencing erratic periods has to do with fat loss and the release of stored hormones and toxins. Adipose tissue is not just a storage space for fat—all kinds of things are stored here! They include fat-soluble vitamins, hormones, pollutants, toxins, and a variety of other substances that are foreign to the body. While stored, they are slowly released into the bloodstream, but they are rapidly freed during weight loss as the fat deposits are burned for energy. As these extra components enter the blood, your hormones and menstrual cycle may be affected. As we know, hormone balance is a delicate process, and even slight increases can trigger deviations in the system. Your body will either metabolize and excrete the excess that's been released or reabsorb it, so any imbalance this causes is only temporary. Ultimately you will be better off, as the pollutants in your body tend to decrease by about 15 percent after weight loss. This also supports the argument for a slow and steady approach to fat loss, as you don't want to load your liver with an overabundance of toxins to metabolize all at once.

Finally, a drop in carbohydrates has the potential to affect thyroid hormone production. For those susceptible to impaired thyroid function, this could also affect your menstrual cycle.

A dramatic drop in carbohydrates can undoubtedly affect your menstrual cycle, specifically if you are at risk of or have a thyroid-related disease. Beginning a keto diet doesn't have to be all or nothing; you don't have to go from high carb to no carb in the blink of an eye. Gradually ease into carbohydrate restriction if cutting carbohydrates quickly is problematic. You can also eat carbs strategically to counterbalance this effect. Listen to the clues your body gives you and adjust your approach accordingly.

Based on excerpts from Keto: A Woman's Guide by Tasha Metcalf with the permission of Quarto Publishing Group. Copyright © 2019.
Want to turn your passion for wellbeing into a fulfilling career? Become a Certified Health Coach! Learn more here.
This ad is displayed using third party content and we do not control its accessibility features.
Tasha Metcalf
Tasha Metcalf

Tasha Metcalf, based near Seattle, Washington, is the creator of the popular website Ketogasm, a resource for women learning how to implement a ketogenic diet. She's the author of the new book Keto: A Woman's Guide and her Hello Keto course has had 58,000 students since its launch in 2017. With a background in biology, nutrition, and functional medicine, Metcalf used the ketogenic diet to reverse PCOS and infertility and lose weight. She has shared her experience with thousands of women looking to utilize the keto diet to improve their health and well-being.