Keto and the Menstrual Cycle: Is There Reason To Worry?

It seems every “keto for women” forum abounds with stories about menstrual cycles gone wild in the first few months of keto. Irregular cycles, breakthrough bleeding, and periods lasting much longer than normal are common complaints. Sometimes these stories are cited as evidence that keto isn’t good for women, at least not premenopausal women, and that we need carbs for healthy hormones. Yet, many women don’t notice any changes in their menstrual cycles at all, while others report improvement in PMS symptoms and cycle regularity from the get-go.

What gives? Why do some women’s cycles apparently become wacky when they start keto, while others feel like keto is the key to period bliss? Can keto “mess up” the menstrual cycle?

We know that diet—what and how much we eat—can profoundly affect our hormones. This is true for both women and men. One of the reasons people are so excited about ketogenic diets is specifically because keto shows promise for helping to regulate hormones and improve cellular sensitivity to hormones such as insulin and leptin.

At the same time, women’s hormones are especially sensitive not only to dietary changes but also to downstream effects such as body fat loss. Furthermore, one of the ways women’s bodies respond to stressors is by turning down the dial on our reproductive systems. It’s reasonable to hypothesize, then, that women might have a tougher time adapting to or sustaining a ketogenic diet. Keto can be stressful depending on one’s approach, and that might negatively impact women’s reproductive health. But do the data actually bear that out, or is so-called “keto period” more misplaced hype than genuine fact?

Note that throughout this post, I’m going to use the term “reproductive health” to refer to all aspects of women’s menstrual cycle, reproductive hormones, and fertility. Even if you aren’t interested in reproducing right now, your body’s willingness to reproduce is an important indicator of overall health. When your reproductive health goes awry—irregular or absent periods (amenorrhea) or hormone imbalances—that’s a big red flag. Of course, post-menopausal women can also experience hormone imbalances that affect their health and quality of life (and low-carb and keto diets can be a great option for them).

Menstrual Cycle 101

Let’s briefly review what constitutes a normal, healthy menstrual cycle, understanding that everybody’s “normal” will be a little different. A typical cycle lasts from 21 to 24 days on the short end to 31 to 35 days on the long end, with 28 days being the median. Day 1 is the first day of your period and begins the follicular phase, which lasts until ovulation. Just before ovulation, levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), and estradiol (a form of estrogen) spike. Next comes the luteal phase covering the approximately 14 days from ovulation to menses. LH, FSH, and estradiol drop, while progesterone rises. Estradiol bumps up again in the middle of the luteal phase. If a fertilized egg is not implanted, menstruation commences, and the whole cycles starts over again. All this is regulated by a complex communication network under the hypothalamic–pituitary–gonadal (HPG) axis, which is closely tied to the actions of the adrenal (the A in HPA axis) and thyroid glands.

Across the cycle, fluctuations in body weight are common as fluid is retained and then released along with shifts in estrogen and progesterone. Changes in blood glucose are also normal, and insulin-dependent diabetics often find that they need to adjust their dose at different times of their cycles to keep their blood sugar in check. The most common pattern is higher blood glucose readings in the pre-menstrual period (the second half of the luteal phase), and lower readings after starting your period and before ovulation. This is generally attributed to the fact that progesterone, which is highest during the luteal phase, is known to reduce insulin sensitivity. However, different women experience different patterns, which can also be affected by other factors such as oral contraceptive use.

Normal fluctuations in insulin resistance and blood glucose can mean that women get lower ketone readings at certain times of the month than others. When these occur premenstrually—and so they tend to coincide with a period of (transient) weight gain and food/carbohydrate cravings—women often feel as though they are doing something wrong. Rest assured that these variations reflect normal physiology.

The many factors that affect your cycle and the levels of your sex hormones include: other hormones, gut health and microbiome, metabolic health (e.g., insulin sensitivity), environmental toxins, stress, sleep, immune health, nutrient deficiencies, activity level and energy expenditure, and age. Each affects the others, and all (except age of course) can be affected by diet. It’s no surprise, then, that it can be extremely difficult to pin down a root cause of menstrual changes or reproductive issues.

What the Research Tells Us About Keto and Menstruation

As I said at the outset, there are lots of anecdotes, both positive and negative. In my experience, most women whose cycles seem to go crazy when they start keto find that things get back to normal—and often a better version of normal—after a few months.

First, it’s tricky to determine the effects of keto per se, since many people combine a ketogenic diet with calorie restriction (intentionally to lose weight or unintentionally due to the appetite suppressing effects of keto) and with fasting (intermittent and/or extended). Each of these can independently impact the factors listed above, lead to weight loss, and affect the menstrual cycle and reproductive health.

So, is there any evidence that keto itself causes changes to menstruation?

The scientific evidence is scant….

The one statistic you’ll see floating around the interwebs is “45% of (adolescent) females experience irregular menstrual cycles on keto.” This statistic comes from one small study of adolescent girls using a therapeutic ketogenic diet to treat epilepsy. Six of the twenty girls reported amenorrhea (loss of period) and three were diagnosed with delayed puberty. However, the ketogenic diet used for epilepsy is different and usually much stricter than an “everyday” keto diet needs to be, and epilepsy is frequently associated with menstrual dysfunction regardless of diet.

To extrapolate the findings of this study and argue that nearly half of teenage girls (or women generally) are likely to experience menstrual problems from going keto is a huge leap.

The fact is, I’m unable to find any studies done in healthy human females (or mice for that matter) demonstrating that otherwise normal menstrual cycles are disturbed by going keto.

5 Ways Keto-Related Factors *Might* Affect Your Menstrual Cycle

With the limited amount of research looking directly at keto and menstruation, let’s look first at whether there are direct effects of carbohydrate restriction or elevated ketone production on the menstrual cycle. Those are the defining characteristics of keto and what differentiates keto from other ways of eating. Then we can examine indirect effects that occur due to factors such as weight loss. These are not unique to keto, though they might be more likely on a ketogenic diet compared to other ways of eating.

Carbohydrate Restriction

There is no real body of evidence that looks at ketogenic levels of carb restriction and menstruation, but there are some clues. In this small study, functional hypothalamic amenorrhea (FHA) was associated with dietary fat restriction; women with FHA actually ate non-significantly more carbs than matched controls and nearly identical total calories. Likewise, in this small study, FHA was associated with lower fat intake but no significant difference in carb intake.

This meta-analysis looked at the effect of low-carb (not keto) diets on markers of reproductive health among overweight women. The researchers found four studies that examined effects on menstruation; all showed improved menstrual regularity and/or ovulation rates. Of six studies that looked at levels of reproductive hormones, five reported significant improvements.

Carb restriction also results in decreased insulin production. Hyperinsulinemia and insulin resistance are frequently associated with polycystic ovarian syndrome (PCOS), one of the leading causes of female infertility and a frequent cause of menstrual irregularity. There is currently a lot of interest in using keto to treat PCOS, but only one small study has so far directly tested the effectiveness of a ketogenic diet to treat PCOS, with positive results.

Ketones

No studies have looked at the direct effects of ketones on menstruation.

Weight Loss

Of course weight loss is not unique to keto, but keto can be very effective for weight loss. Some women experience rapid weight loss when first starting a keto diet. Weight loss in and of itself can impact menstruation through a variety of pathways (and, of course, keto isn’t the only way people lose weight). A key way is by reducing the hormone leptin. Leptin’s main job is to communicate energy availability to the hypothalamus—high levels of leptin tell the hypothalamus that we have enough energy on board, which also means we can reproduce. Low leptin can disrupt the menstrual cycle and is linked to hypothalamic amenorrhea.

Body fat loss can also affect estrogen levels since estrogen is both stored and produced in adipocytes (fat cells). While fat loss in the long term will decrease estrogen production, it is possible that rapid fat loss might temporarily raise estrogen levels and can also affect estrogen-progesterone balance. These transient changes in estrogen levels might underlie some of the menstrual irregularities women report.

Stress

Stress can impact the menstrual cycle in myriad ways. Cortisol acts on the hypothalamus and pituitary glands, affecting hormone levels, sleep, immune function, and gut health, to name a few. Diets can be a source of stress, both at the physiological and psychological levels. Keto has a reputation for being especially stressful because it is more restrictive than other low-carb diets, but this can be mitigated by following the Keto Reset tips for women.

Thyroid Function

Thyroid dysregulation is another common cause of menstrual irregularities, and there remains a pervasive belief that keto is bad for thyroid health. Indeed, the thyroid is sensitive to nutrient deficiencies and caloric restriction, and thyroid hormones, especially T3, do frequently decline on keto. However, as Mark has discussed in a previous post, changes in T3 levels might not be a problem, especially in the absence of other problematic symptoms. Moreover, many practitioners now use keto as a cornerstone in their treatment of thyroid disorders.

What Should I Take From These Findings?

The first takeaway: there just isn’t much direct evidence about how keto might affect your menstrual cycle, positively or negatively. We have some studies suggesting that low-carb diets improve some aspects of menstruation and reproductive health, but keto is more than just another low-carb diet. Ketones themselves have important physiological properties, such as being directly anti-inflammatory, which might positively impact women’s reproductive health.

Second, the ways that keto is likely to (negatively) affect menstruation aren’t unique to keto, they’re common to any diet: hormone shifts mediated by energy balance, stress, and weight loss.

Furthermore, since keto is so often combined with caloric restriction, time-restricted eating, and fasting, even the anecdotal evidence might not be able to tell us all that much. If a woman is eating ketogenically, in a big caloric deficit, and doing OMAD (one meal a day), and her leptin plummets, how are we to know what really caused it? We don’t have good evidence that otherwise healthy women start a well-executed ketogenic diet and end up messing up their menstrual cycles.

That said, women do need to be cognizant of the sum total of the signals they are sending their bodies when it comes to energy availability and stress. A lot of women come to the keto diet with a history of adrenal, thyroid, metabolic, and reproductive issues. It’s important that they’re extra careful about how they approach keto. Done correctly, it might be just what the doctor ordered. I encourage any woman who’s dealing with other hormonal issues to work with a medical practitioner to tailor a keto diet to her unique needs.

But I’m Telling You, Keto Made My Period Go Haywire!

Ok, I believe you, really! But changes do not necessarily equal dysfunction. It is normal to experience hormone fluctuations when you make a massive—or even a relatively small but important—shift in your nutrition. Sometimes those fluctuations are unpleasant or unwanted, such as a period that lasts 14 days or one that arrives a week before you planned while you’re on vacation. However, that doesn’t make them bad from a health perspective. We need to respect that our bodies are dynamic systems. Changing the input will invariably change the output, and the system might need a few months to adapt to a new normal.

If your cycle goes wonky but you’re otherwise feeling good, give it a few months to sort itself out. If after a few months it’s still all over the place (or definitely if you’re having other disruptive symptoms), enlist help. In the meantime, check to make sure you’re not short-changing yourself nutritionally or calorically. Scale back on fasting efforts, and consider shifting more toward a traditional Primal way of eating.

At the end of the day, if you go keto and experience negative effects, stop. Keto is super hyped right now, but if your body is sending you clear signals that keto is not a good approach for you at this time, don’t do it. You can always try again later. It might be that your first attempt at keto didn’t work, but with a few adjustments and some experimentation over time you can find a version of keto that works for you.

Thanks for reading, everyone. Do you have comments, questions, or feedback? Let me know below.

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References:

Comninos AN, Jayasena CN, Dhillo WS. The relationship between gut and adipose hormones, and reproduction. Human Reproduction Update 2014; 20(2): 153–174.

Fontana R, Della Torre S. The Deep Correlation between Energy Metabolism and Reproduction: A View on the Effects of Nutrition for Women Fertility. Nutrients. 2016;8(2):87.

Klok MD, Jakobsdottir S, Drent ML. The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obesity Reviews 2007;8(1):21-34.

Meczekalski B, Katulski K, Czyzyk A, Podfigurna-Stopa A, Maciejewska-Jeske M. Functional hypothalamic amenorrhea and its influence on women’s health. J Endocrinol Invest. 2014;37(11):1049–1056.  

Tena-Sempere M. Roles of Ghrelin and Leptin in the Control of Reproductive Function. Neuroendocrinology 2007;86:229-241.

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13 Keto-Friendly Fiber Foods

While some keto or low-carb proponents claim fiber is useless at best and actively harmful at worst, I come down on the side that says fiber is probably helpful for most people. Some folks have persistently better responses to low- or no-fiber keto diets, and I won’t argue with that—I’ve seen it happen and I’ve read the studies where de-emphasizing fiber can actually improve constipation, for example.

I’ll just say that I have an opposite reaction, and, most importantly, I love eating a variety of plant foods that also happen to contain a ton of great nutrients in addition to fiber.

Do I buy into the idea that fiber is important because it is every human being’s responsibility to produce as much colonic bulk as humanly possible? No.

Do I think we should be consistently pushing the limits of our digestive tracts, performing feats of bathroom heroism so momentous they border on Herculean, and making sure the toilet bowl buckles beneath us? No.

The real value of fiber lies not in its coarseness, its tendency to form colonic bulk, to keep us topped off. The true value lies in its fermentability. A fermentable fiber is a prebiotic fiber—fiber that feeds our gut bacteria.

I won’t get into the many roles our gut bacteria play in our health today (I’ve covered that before. 1, 2, 3).

I will, however, explain why we need to be feeding our gut bacteria. Our gut bacteria form a physical barrier against incursions and colonization by pathogenic bacteria; they take up room along the gut lining so pathogens can’t. If we don’t feed our gut bacteria with prebiotics, it won’t be around to protect us. After antibiotic treatment where both good and bad gut flora are indiscriminately targeted and wiped out, pathogenic obesity-promoting bacteria take advantage of the open space. That’s a worst-case scenario, but it shows what can happen when the harmony of the gut is disturbed by antibiotics or, to a less extent, a lack of fermentable prebiotic fibers.

When our gut bacteria eat prebiotics, they also give off metabolites like butyric acid—a short chain fatty acid that our colonic cells use as an energy source and which improves metabolic health.

Gut bacteria also convert antinutrients like phytic acid into nutrients like inositol. The almond meal-obsessed keto eater would do well to have a powerful gut biome set up to convert all that phytic acid to inositol.

Now, some writers will come up with specific blends of fibers, powders and gums to create the “optimal” prebiotic diet for your gut bacteria, but that’s pretty silly. The gut is a complicated place. We’ve barely begun to even identify all its inhabitants. To think we know the precise blend of isolated fiber that will make them flourish, and then act on that, is a mistake.

A better option is to eat foods that contain fiber. Some of the prebiotic fibrous foods with the best nutrient profiles also happen to be extremely keto-friendly.

1) Almonds and Pistachios

Nuts are usually favored in health-conscious circles for a few reasons. They like the monounsaturated fat. They like the mineral profile, or the complete protein, or their ability to dissemble into nut meals and form baked goods. But what gets short shrift is the fiber content. Now, I can’t speak for other nuts, but almonds and pistachios in particular contain fiber with potent prebiotic effects. People who eat almonds and to an even greater extent pistachios end up with improved gut bacteria profiles.

2) Green Bananas

Ripe bananas are difficult to squeeze into a ketogenic diet. The green banana—an unripe one—is mostly resistant starch, a type of starch that cannot be digested and travels untouched until colonic bacteria metabolize it. It’s one of the best stimulators we know of butyric acid production. And sure, you could do a spoonful of raw potato starch to get your resistant starch, but the beauty of the green banana is that it also provides potassium, another nutrient that some find difficult to obtain and stay keto.

3) Wild Blueberries

Blackberries, boysenberries, raspberries, and strawberries are all loaded with fiber, and you should eat them. They’re lower carb than you think, they’re loaded with polyphenols, and topped with some real whipped cream they make a fantastic dessert. But wild blueberries are special. They’re smaller than other berries, which increases the amount of skin per ounce you get, and skin is where all the polyphenols and fiber lie. Heck, even the blueberry’s polyphenols have prebiotic effects on the gut biome.

4) Mushrooms

A few years ago, I wrote a whole post on mushrooms. Suffice it to say, they’re quite wonderful, bordering on magical. I did not discuss the fiber they contain. It turns out that all the various mushroom polysaccharides/fibers, including beta-glucans, mannans, chitin, xylans, and galactans also act as potent prebiotics that improve the health of the host.

5) Avocado

Your standard avocado has about 12-15 grams of fiber, if you eat the whole thing. I

6) Jicama

Great with chili powder, salt, and lime juice, jicama is about 11 grams of carbs per cup, but half of those are inulin, a potent prebiotic fiber with a tendency to really ramp up butyrate production.

7) Onions

Onions are another fantastic source of inulin. They go into almost every dish of every cuisine, so there’s no excuse not to be eating onions.

8) Garlic

I’ve been known to treat garlic like a vegetable, roasting an entire cast iron pan full until brown and sweet and chewy. They’re another great source of prebiotic fiber.

9) Leeks

Leeks have more inulin than onions. Try them crispy in egg scrambles.

10) Broccoli

Broccolini is a major part of my favorite meal of the day—my Big-Ass Keto Salad. Broccoli (and cruciferous vegetables in general) has been shown to have modulatory effects on the gut biome.

11) Sauerkraut

Kraut gives you two in one. It’s a fermented food, which is great for the gut biome. And it’s cabbage, which is very fibrous. Even pasteurized kraut improves gut health.

12) Dark Chocolate

Dark chocolate, the good stuff with a high cacao content (85%+) and low sugar content, is an incredible source of prebiotic fiber. Eat more of it.

13) Animal Fiber

Obligate carnivores like cheetahs who don’t eat any plants (willingly) still have gut bacteria. These gut bacteria thrive on “animal fiber,” the gristle and cartilage and other bits of connective tissue that comprise a good 20-30% of the walking weight of a prey animal. Humans are not obligate carnivores, but eating the entire animal has been a mainstay of advanced hominid existence for millions of years. I find it very likely that something, someone, somewhere inside our guts is breaking down the animal fiber we eat—so you’d better be eating some!

Not so tough, is it? It’s not like I’m suggesting you load up on bran muffins, psyllium smoothies. I don’t want you dumping flax meal into everything or munching on those awful fiber gummies. Just eat some basic, healthy, low-carb plant matter—foods that don’t really scream “fiber”—and the rest will take care of itself.

What’s your favorite low-carb source of fiber? Let me know down below.

Thanks for reading, everyone.

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References: 

Hernández E, Bargiela R, Diez MS, et al. Functional consequences of microbial shifts in the human gastrointestinal tract linked to antibiotic treatment and obesity. Gut Microbes. 2013;4(4):306-15.

Ukhanova M, Wang X, Baer DJ, Novotny JA, Fredborg M, Mai V. Effects of almond and pistachio consumption on gut microbiota composition in a randomised cross-over human feeding study. Br J Nutr. 2014;111(12):2146-52.

Jiao X, Wang Y, Lin Y, et al. Blueberry polyphenols extract as a potential prebiotic with anti-obesity effects on C57BL/6 J mice by modulating the gut microbiota. J Nutr Biochem. 2019;64:88-100.

Jayachandran M, Xiao J, Xu B. A Critical Review on Health Promoting Benefits of Edible Mushrooms through Gut Microbiota. Int J Mol Sci. 2017;18(9)

Nielsen ES, Garnås E, Jensen KJ, et al. Lacto-fermented sauerkraut improves symptoms in IBS patients independent of product pasteurisation – a pilot study. Food Funct. 2018;9(10):5323-5335.

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Dear Mark: Protein Efficiency in Seniors, Earned Carbs, Hardgainer with Limited Time

For this week’s edition of Dear Mark, I’m answering three questions from readers. First, is the reduced protein efficiency in older adults due to inactivity, or is it something inherent to the aging process, or both? Second, how does a person know if they’ve actually “earned” any carbs? Does everyone on a keto diet earn carbs by virtue of exercising, or is there more to it? And finally, how can a hardgainer with a packed schedule all week long and limited gym time maintain what little muscle mass he’s managed to gain?

Let’s find out:

Interesting observation on protein needs and training in Sunday with Sisson – general consensus is that older folks need more protein as they age but maybe that’s because they are less active and not simply a result of aging.

That’s probably part of it, but it’s not all of it.

In studies where they compare resistance training seniors who eat extra protein with resistance training seniors who don’t, only the seniors eating extra protein gain muscle mass.

Now, it may be that a lifetime of inactivity degrades your ability to utilize protein, and if these older adults had always lifted weights they would have retained their protein efficiency. But maybe not. As it stands, all else being equal, an older adult needs more protein to get the same effect, even if he or she is lifting weights.

Enjoyable read. As someone who lives a ketogenic lifestyle, and who is athletically active, I am not sure exactly how to go about consuming the carbs I’ve “earned.” I rarely run into problems with athletic energy, at least not below anaerobic threshold. Not sure that eating more carbs will improve my performance. And, if they would improve my performance, how does one go about calculating earned carb replacement without losing the fat burning benefits of ketosis?

It sounds like you’re in a good place.

When I say “eat the carbs you earn,” I’m talking to the people who do run into problems with athletic energy, poor performance, insomnia, and other symptoms of exercise-induced stress. Typically, the people who “earn their carbs” are doing stuff like CrossFit, high volume moderate-to-high intensity endurance work, martial arts training, and team sports.

I doubt extra carbs will improve your performance if most of your training takes place in the aerobic zone. But if you wanted to experiment, you could try a small sweet potato immediately after a workout where you passed the anaerobic threshold.

That’s the best way to determine if you’ve earned carbs. Eat 20-30 grams after a workout and see if you enjoy performance gains without gaining body fat. There’s no consumer-friendly way to directly calculate carb debt; self-experimentation is it.

I recently took a job that has me out of bed at 4am and not home until 6pm Monday Through Friday. Is there an efficient way I can maintain muscle mass only lifting weights Saturday and Sunday? I’m a hardgainer at 5’10” and only 140lbs. I’m afraid giving up my 5 day split will ruin what muscle I’ve been able to gain.

Any hardgainer has to eat, and eat, and eat. Increase your food intake. Just eat. Stick to healthy Primal fare, but pack in the food. Meat, milk, veggies, potatoes, rice, eggs, avocados, fruit. Throw some liver in, too (old bodybuilder staple). It doesn’t sound like fat gain is an issue for you, so I’d take advantage of that and just consume calories.

As for training, get some exercise snacks in during the week.

As soon as you wake up, do a quick superset of pushups. Do as many pushups as you can. Wait 30 seconds. Do as many pushups as you can. Wait 30 seconds. Do as many pushups as you can. There you go. That shouldn’t take more than 5 minutes in the morning. Can you squeeze that in?

Repeat this every morning with a different exercise. Pullups, bodyweight rows, kettlebell swings, handstand pushups, dips, bodyweight squats, goblet squats, reverse lunges, reverse weighted lunges. Just choose one thing to do every morning, cram as many reps as you can using the same format (max reps, 30 s rest, max reps, 30 s rest, max reps). Buy any equipment you can if you choose to use weights.

When you get home at night, do the same thing with a different exercise. Morning pushups, evening KB swings, etc. That way, you get about 10 minutes per weekday of intense strength training without impacting your sleep or schedule in any real meaningful way.

Make sure your sleep hygiene is rock solid. Dim those lights at night, turn on f.lux or night mode, wear the blue blocking goggles, get to bed (ideally) by 8:30, 9 to give you 7 to 7.5 hours of sleep. Sleep is essential for gaining lean mass (and staying healthy in general).

On the weekend, hit the weights hard on both days, hitting the entire body. Go high volume/reps. If size is your goal, dropping the weight a bit and focusing on range of motion and a high rep count (10-15 per set) is very effective.

Food, sleep, reps. Good luck!

Thanks for stopping in today, everybody. Additional thoughts for these folks—or questions of your own? Share them below.

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References:

Tieland M, Dirks ML, Van der zwaluw N, et al. Protein supplementation increases muscle mass gain during prolonged resistance-type exercise training in frail elderly people: a randomized, double-blind, placebo-controlled trial. J Am Med Dir Assoc. 2012;13(8):713-9.

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