Many people are increasingly interested in healthy ways to manage their weight, leading them to explore trendy diets. However, it's important to understand how these dietary changes, especially drastic ones, can affect your body, particularly your menstrual cycle. The foods you eat can significantly impact your hormones and overall body composition, especially if you're not getting the right balance of nutrients.
How Diet Changes Affect Your Period
Drastic changes in diet can affect your menstrual cycle. It’s important to know how changing your diet changes your period and to track any changes you need to inform your doctor about. Because hormones play such a major role in your body’s ability to lose or gain weight, your period and overall menstrual cycle will also be affected. In addition, drastic changes in your diet could lead to fertility issues. In addition, if you’re dealing with severe PMS symptoms, changing your diet could positively impact your cycle.
The Ketogenic Diet: An Overview
The ketogenic diet, often shortened to keto, is a low-carb, high-fat diet. This diet aims to lower blood sugar and insulin levels, shifting the body's metabolism away from carbohydrates and toward fat and ketones. When your body is at its best to burn for energy, reaching this metabolic state is referred to as ketosis. If you choose a keto diet, your meals will typically contain 70% fat, 20% protein, and less than 10% of carbs. Before starting any diet, especially one as restrictive as keto, consulting with your doctor is essential.
Can Keto Affect Your Period?
The answer is yes, the keto diet can affect your period. If you begin to lose weight at a faster rate, your period may skip or vanish altogether. One of the most common effects on how the keto diet affects your period is the decrease in estrogen. Hormone changes can make your cycle more irregular and even cause period spotting on a keto diet.
Keto and Menstrual Irregularities: What the Research Says
Recent studies also point to keto’s effects on menstrual irregularities with unknown causes. In a study of women on either low-fat diets or keto diets, researchers only observed changes in menstruation in the women on keto. Women observing a low-carb diet reported changes in either the frequency of their periods or the intensity of their periods after starting the diet. While keto is an excellent weight loss tool, the participants’ weight didn’t seem to factor into the results. Both groups experienced improved cholesterol levels and body composition. Only those on keto and/or ketone supplements saw menstrual changes. Researchers say this suggests a clear link between blood ketones and menstrual physiology. That’s the biological process that regulates the menstrual cycle and is so important to fertility and overall reproductive health. On the other hand, keto can also lead to menstrual irregularities in some women, especially during the initial stages as your body adjusts to the new diet. The irregular or disappearing periods can be traced to hormone changes.
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The Role of Hormones
"To have a normal period, you have to have a pulsatile release of hormones from the brain," Dr. Thoppil says. "Any sort of stressor - weight loss or a lot of exercise - can affect that pulsatile release that has to happen for this normal choreography of hormone release that allows you to have regular menses." A study published in September 2018 in the Journal of Obesity and Weight Loss Therapy noted that keto caused disruption to women’s hormonal systems.
One of the main hormones in play here is estrogen, which is responsible for regulating the menstrual cycle. As weight drops, so do estrogen levels, says Luiza Petre, MD, a board-certified cardiologist and nutrition expert based in New York City. According to previous research, when participants lost an average of 17 pounds, their levels of the estrogen hormone estrone decreased 5.7 percent and the estrogen hormone estradiol dropped nearly 10 percent. The study authors note that weight loss as a result of calorie restriction and exercise significantly decreased estrogen levels.
Another hormone that seems to mess with period regularity is the gonadotropin-releasing hormone (GnRH). GnRH is the signal for pituitary production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are responsible for stimulating ovarian production of estrogen and progesterone, and therefore ovulation). A small study published in the Journal of Translational Medicine in February 2020 found overweight women with PCOS who followed the keto diet for 12 weeks lost a significant amount of weight and also saw a decrease in the ratio between LH and FSH, which is a healthier balance between the two.
Increasing ketones in the blood through a keto diet or supplements may help put irregular menstrual cycles back on schedule or even restart a period that appears to have stalled for good, new research suggests.
In a study comparing weight loss results on low-fat and ketogenic diets with and without the addition of ketone supplements, 11 of 13 pre-menopausal participants who achieved nutritional ketosis reported at least one change in menstrual frequency, intensity - or both - during the intervention.
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Women on low-fat diets did not report any change to their periods. All women had lost the same relative percentage of weight. Their average age was 34, and all were healthy but overweight.
“There were six women who hadn’t had a period in over a year - who felt like their typical cycles were over. And their periods actually restarted on the diet,” said Madison Kackley, lead author of the study and a research scientist and lecturer in human sciences at The Ohio State University.
“Our hypothesis after seeing these results is that the presence of ketones may help regulate women’s health in regard to endocrine, cognitive and metabolic influences.”
The study was published recently in PLOS ONE.
Potential Benefits of Keto on PMS Symptoms
Premenstrual syndrome (PMS) is a catch-all term used for a wide range of symptoms many women experience before the start of their period. Following a keto diet can alleviate some of these symptoms thanks to its effects on blood sugar, inflammation, and hormonal balance. For example, reducing your intake of carbs can reduce insulin spikes. Keto may improve your sleep. If you deal with insomnia before your period, keto’s effects on blood sugar and neurotransmitters like gamma-aminobutyric acid (GABA) can help you get better rest. Keto reduces cravings. By lowering your carb intake, you’ll automatically control your blood sugar, a common culprit behind sweets cravings. Being in a state of ketosis may also help lower levels of ghrelin, your hunger hormone, to prevent weight gain. Keto is highly anti-inflammatory. Inflammation causes hormone fluctuations that can lead to period cramps, gastrointestinal discomfort, and other painful PMS symptoms. A boost in ketones like beta-hydroxybutyrate (BHB) may help block inflammatory responses. Ketones support cognition. Many report better memory and concentration when following keto. This is likely due to an increase in the protein brain-derived neurotrophic factor (BDNF) as well as the enhanced bioavailability of ketones in the brain.
Read also: Magnesium Supplements for Keto
Weight Loss, Leptin, and Amenorrhea
While there isn’t much research to support that ketosis itself messes with menstruation, there are things that can happen on any diet to send certain signals to your body. Weight loss can be a great way to balance your hormones and keep your body operating efficiently. When it happens too fast, it can lead to an imbalance in estrogen and progesterone levels and amenorrhea, or the absence of menstruation, and spotting between periods. Most people on keto also find they’re eating fewer calories than before. When leptin is in range, it tells your body that it’s safe to reproduce. When leptin signaling dials down, your brain gets the message that it’s not a safe time for reproduction. The result is something called functional hypothalamic amenorrhea. Functional hypothalamic amenorrhea is your brain’s way of preserving energy for your body but shutting down your menstrual cycle. Stress can have the same effect.
Keto and Specific Hormonal Conditions: PCOS
The keto diet can significantly affect hormones like insulin, cortisol, and reproductive hormones. The absence of excess insulin gives your sex hormones a chance to find natural balance. This can improve ovulation, reduce androgens, and improve symptoms of polycystic ovary syndrome (PCOS). It may also prevent type 2 diabetes and obesity, common complications of PCOS.
Keto also influences cortisol, your body’s stress hormone. Much like intermittent fasting, you may trigger a stress response in the short term. Finally, ketosis can affect reproductive hormones. Studies show keto may reduce excess testosterone elevated in conditions like PCOS and support a balance of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
Insulin resistance, a common issue for women with PCOS, leads to elevated insulin levels that can trigger excess androgen production. By drastically reducing your carbohydrate intake, keto lowers blood sugar and insulin levels, improving insulin sensitivity. Keto can also make it easier for you to lose weight, a common concern for women with PCOS. Getting to a healthier weight and staying there isn’t just good for your mental health.
The Importance of Tracking Your Cycle
Everyone’s cycle is different, so understanding how your personal cycle works is the first step in taking control of your health and hormones. If you don’t already have some way of tracking your cycle, apps can help. You can also keep a hormone journal. It can be very easy to forget how bad your cramps were a couple of months ago when you’re not feeling them anymore. This helps you better identify subtle changes happening in your body before you start addressing them with diet or lifestyle changes.
Supporting Hormonal Health Through Diet and Supplements
Certain foods can help you optimize your hormonal health during each phase of your menstrual cycle. You can also use diet to manage PMS symptoms. You should always start with diet when targeting your hormonal health, but supplements can help address existing nutritional deficiencies or fill in the gaps where your diet falls short.
- Fiber: Healthy levels of fiber support balanced estrogen levels and a healthier gut microbiome, a key component of hormonal health.
- Fish oil supplements: If you’re not getting omega-3s from dietary sources like fatty fish, try fish oil. Research shows it works better than ibuprofen for period cramps.
- Krill oil: Studies show supplementation with krill oil lowers stress levels, improves mood, and decreases the use of over-the-counter pain medications.
- Magnesium: Studies show this nutrient can reduce food cravings, mood swings, depression, and fatigue during your period.
- Vitamin B6: This one is an all-star in combating PMS symptoms like breast pain and bloating. It may also reduce depression risk when hormones aren’t in balance.
- Vitamin D: Low vitamin D levels are linked to menstrual irregularities.
The Impact of Stress and Exercise
Another chemical that can wreak havoc on your hormones is cortisol. The big issue with cortisol and hormone balance is that your sex hormones share the same precursor as cortisol - pregnenolone. (19) When stress is high, you use more pregnenolone to make cortisol, leaving little left for your sex hormones. Finding ways to deal with your stress is then vital for balancing your hormones. Exercise, meditation, and deep breathing can all be positive destressors.
If you’re not moving your body in some way or another every day then you’re missing out on an important aspect of hormone balancing and overall wellness.
Navigating Changes and Seeking Guidance
While many women report changes in their menstrual cycle during the first few months of keto, many others find a healthier cycle on the other side of keto. If you find yourself with any unwelcome changes to your cycle, there are plenty of modifications to the diet that you can try for healthier hormonal health.
Additional Research Findings
A recent study suggests the ketogenic diet could positively impact menstrual cycles by boosting ketones, potentially unlocking new therapeutic insights for women’s reproductive health. Irregular menstrual cycles may be mediated by a ketogenic diet (KD) which increases ketones in the blood, according to a recent study published in PLOS One.1In a KD, fat is converted into ketones, which cells in the body and brain use as an alternative to glucose. The goal of a KD is to put the body in nutritional ketosis, which refers to a state in which the body has greater access to ketones for fuel and as a signaling molecule.1A change in menstrual frequency, intensity, or both was reported in 11 of 13 pre-menopausal patients achieving nutritional ketosis in a study evaluating weight loss in KDs, vs no change among women on low-fat diets (LFDs). This led investigators to hypothesize ketones may help regulate menstrual health in women.
The study was conducted to evaluate the impact of KD on stalled menstruation. Participants included premenopausal women aged a mean 34 years residing in the greater Columbus, Ohio area.2Patients on a KD consumed approximately 40 g of carbohydrates daily, with the remaining non-protein calories obtained from fat. In comparison, those on an LFD received 25% of energy from lipids, with less than 10% being saturated fat and less than 30 g of added oils.2Women with major weight loss events, habitual consumption of a low-carbohydrate diet, gastrointestinal disorders or food allergies, excess alcohol consumption, disease conditions, or diabetic medication use were excluded from the analysis. Participants completed questionnaires about medical history, physical activity, and menstrual history.2Diet use lasted for 6 weeks, with participants attending bi-weekly in-person visits. Weight and height were measured, alongside body composition using dual x-ray absorptiometry. A trained phlebotomist used aseptic techniques to perform blood draws.2Menstrual events were reported subjectively through the lifestyle changes survey. Changes were recorded on days 14, 28, and 42. Patients responding positively to questions asking if changes occurred were then asked if menstrual events differed in intensity, frequency, or if they were regained after 1 year or longer.2Baseline characteristics did not significantly differ between groups, with similar capillary beta-hydroxybutyrate (R-βHB) reported. However, participants on the KD had R-βHB boosted further than the LFD into the range of nutritional ketosis. R-βHB concentrations were not impacted by LFD.2Significant changes were reported for all menses categories for both KDs assessed. This included KD with ketone salts (KS) or with flavor-matched placebo (PL). Both KD+KS and KD+PL had significant differences in the “no change” response at days 28 and 42 when compared to LFD.2A significant elevation in body mass index (BMI) was reported in participants with a change in menstrual patterns vs those with no response. An increase in serum MCP-1 levels was also reported in these participants.2Clinically meaningful weight loss was reported among women with a KD+PL diet at day 14, along with those on the KD+KS and the LFD by day 28. Reversing a class 1 obesity BMI to an overweight BMI was reported in 64% of patients with obesity class 1 at baseline.2Patients on the LFD had a significantly reduced mean fasting insulin vs the KD+KS. Inflammatory markers were not impacted by weight loss.2These results indicated clinically significant weight loss from both a KD and LFD, with a KD linked to a positive impact on self-reported menses. Investigators concluded further research may highlight novel therapeutic roles of ketosis.
Low Carb Diets and Hormones: A Closer Look
Studies show that low carb diets can cause weight loss and improve metabolic health (1). However, although low carb diets are great for some people, they may cause problems for others. Any diet that severely restricts calories, including some low carb diets, may disrupt certain hormones in some women (2).
The HPA Axis and Low Carb Diets
Your hormones are regulated by three major glands:
- Hypothalamus: located in your brain
- Pituitary: located in your brain
- Adrenals: located at the top of your kidneys
All three glands interact in complex ways to keep your hormones in balance. This is known as the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is responsible for regulating your stress levels, mood, emotions, digestion, immune system, sex drive, metabolism, energy levels, and more (3). The glands are sensitive to things like calorie intake, stress, and exercise levels.
Long-term stress can cause you to overproduce the hormones cortisol and norepinephrine, creating an imbalance that increases pressure on the hypothalamus, pituitary, and adrenal glands (4). This ongoing pressure may eventually lead to HPA axis dysfunction. Although you may have heard the term “adrenal fatigue” associated with similar health concerns from long-term stress, this is not a medical term and its use is controversial. The accepted medical term is HPA axis dysfuntion (5, 6).
Symptoms of HPA axis dysfuntion include sleep problems, a weakened immune system, and a greater risk of long-term health problems such as cardiovascular disease, stomach ulcers, and mental health conditions (7). Studies of diet changes in people with obesity suggest eating too few calories can act as a stressor, increasing production of cortisol - commonly known as “the stress hormone.” However, many of these studies reported no problems with HPA axis function (2).
An older 2007 study found that, regardless of weight loss, a low carb diet increased cortisol levels compared to a moderate-fat, moderate-carb diet. But these researchers studied obese men only. More evidence is needed to understand the connection between diet and cortisol levels (8).
Eating too few carbs or calories and experiencing chronic stress may disrupt the HPA axis, causing hormonal problems.
Menstrual Irregularities and Amenorrhea
If your diet is very restrictive, you may experience irregular menstrual cycles or amenorrhea. Amenorrhea is defined as the absence of a menstrual cycle for 3 months or more. The most common cause of amenorrhea is functional hypothalamic amenorrhea, which can result from a very low calorie diet, disordered eating, losing weight, experiencing stress, or getting too much exercise. Restricting carbs could contribute to some of these causes (9).
Amenorrhea occurs as a result of the drop in levels of many hormones, such as gonadotropin-releasing hormone, which starts the menstrual cycle (9). This results in a domino effect, causing a drop in the levels of other hormones such as luteinizing hormone, follicle-stimulating hormone, estrogen, progesterone, and testosterone (11).
These changes can slow some functions in the hypothalamus, the region of the brain responsible for hormone release. A low level of leptin, a hormone produced by fat cells, is another potential cause of amenorrhea and irregular menstruation. Research suggests that women need a certain level of leptin to maintain normal menstrual function (12, 13).
If your carb or calorie consumption is too low, it may suppress your leptin levels and interfere with leptin’s ability to regulate your reproductive hormones. This is particularly true for underweight or lean women on a low carb diet.
In a 2021 narrative review of research on female athletes and their diets, the authors reported that female athletes often underconsume in calories, especially carbohydrates, and that this can affect menstruation and other important metabolic processes (14). However, research on amenorrhea and low carb diets is still scarce. Studies that report amenorrhea as a side effect were usually done only in women following a predominately low carb diet for a long period of time (15).
One small 2003 study followed 20 teenage girls using a ketogenic (very low carb) diet to treat epilepsy. Researchers found that 45% experienced menstrual problems and 6 experienced amenorrhea during the 6-month study period (16).
Following a very low carb (ketogenic) diet over a long period of time may cause irregular menstrual cycles or amenorrhea.
Carbs and Thyroid Function
Your thyroid gland produces two hormones: thyroxine (T4) and triiodothyronine (T3). These two hormones are necessary for a wide range of bodily functions, including breathing, heart rate, the nervous system, body weight, temperature control, cholesterol levels, and the menstrual cycle. In a study of people with breast cancer, the ketogenic diet in particular had no adverse effects on thyroid function. In fact, the diet had beneficial effects in that it significantly reduced levels of lactate and alkaline phosphatase (17). However, other studies have found that carbohydrates can be beneficial for thyroid function and that consuming too few of them can actually lower thyroid hormone levels (18).
Very low carb diets may cause a drop in thyroid function in some people. This may result in fatigue, weight gain, and low mood.
How Many Carbs Should You Eat?
The optimal amount of dietary carbs varies for each individual. However, the Dietary Guidelines for Americans recommend that carbs make up 45-65% of your daily calorie intake (19). Furthermore, the Food and Drug Administration states that for a 2,000-calorie diet, the Daily Value for carbs is 275 grams per day (20).
Moderate Carb Intake: Potential Benefits
A large 2018 study looked at carb intake in middle-aged adults. In this group, eating a moderate amount of carbs - that is, 50% to 55% of your total calories - was associated with the lowest risk of dying. This means that people with a moderate carb intake were likely to live longer than people with low or high carb diets (21). There are other reasons to consider a moderate carb intake. Given the potential side effects of restictive diets, certain women may do better consuming a moderate amount of carbs.
This may include women who:
- are very active and struggle to recover after training
- have an underactive thyroid, despite taking medication
- struggle to lose weight or start gaining weight, even on a low carb diet
- have stopped menstruating or are having an irregular cycle
- have been on a very low carb diet for an extended period of time
- are pregnant or breastfeeding
For these women, benefits of a moderate-carb diet may include weight loss, improved mood and energy levels, normal menstrual function, and better sleep. Other women, such as athletes or those trying to gain weight, may find a higher daily carb intake appropriate. Your doctor or a registered dietician can help you create a healthy eating plan.
A moderate carb intake may benefit some women, including those who are very active or have menstrual problems.
Low Carb Intake: When It Might Be Beneficial
Certain women may do better sticking to a low carb diet. This includes women who have (22, 23, 24, 25, 26):
- overweight or obesity
- a very sedentary lifestyle
- epilepsy
- polycystic ovary syndrome, fibroids, or endometriosis
- yeast overgrowth
- insulin resistance
- type 1 or type 2 diabetes
- a neurodegenerative condition such as Alzheimer’s disease or Parkinson’s disease
- certain forms of cancer
Note that “low carb” is defined differently across studies. Some diets were very low carb, in the range of 15 grams to 20 grams per day. On the higher end, some diets were less restrictive, with low carb defined as less than 45% of daily calories from carbs.
A lower carb intake may benefit women with obesity, epilepsy, diabetes, polycystic ovary syndrome, and some other conditions.