The restriction of calories during intermittent fasting may lead to hormonal disturbances. However, intermittent fasting and menstruation will not become an issue if you pay attention to your body.
Learn the different phases of your menstrual cycle and the most appropriate fast lengths and food choices to make during the month. This will give you the greatest intermittent fasting success without an increase in period problems.
Men and women lose weight differently. Some general intermittent fasting rules apply to both sexes, but there are some ladies-only things to consider when fasting.
Unless they are in menopause, women experience hormonal changes every month from their menstrual cycle. Intermittent fasting also has hormonal effects on a woman. These effects may change a woman’s menses (periods).
Approximately 25% of women have issues with heavy, irregular, or painful periods (1). The last thing you want to do if you’re already having menstrual problems is exacerbate them with fasting.
Women need to understand the phases of the menstrual cycle because intermittent fasting and eating recommendations will be different for each phase.
The menstrual cycle starts with the follicular phase for days 1-14. The first 5 days of the follicular phase is when a woman menstruates. During this time, women experience lowered hormone levels and often decreased energy, especially during the first few days.
The ovulatory phase is next in the cycle on days 14-15. Estrogen and energy levels are at their highest.
During days 15-28, the luteal phase, hormones surge and lower as the body prepares to start the cycle over again.
Many women have questions about how intermittent fasting will affect menstruation.
During intermittent fasting, calories are restricted or avoided altogether for a set period of up to 24 hours, depending upon which method of fasting you choose to follow. Prolonged fasting refers to refraining from eating for 1-3 days. During these longer fasts people sometimes decide to do a water fast, consuming zero nutrients for the duration.
It is not a problem to do intermittent fasting during any phase of the cycle, but it is recommended to avoid longer fasts or water fasts while menstruating.
Your period may present differently when intermittent fasting due to calorie restriction and the decreased release of the hormones needed for normal menstruation.
The part of the brain that regulates hormones (the hypothalamus) is affected when calories are restricted. The hypothalamus may not secrete the gonadotropin-releasing hormone (GnRH) needed to trigger the release of the reproductive hormones, which play a significant role in menstruation (2). Without the release of these hormones, communication with the ovaries breaks down, and problem periods occur.
There is little research in intermittent fasting and menstruation, but one study using rats reported a decrease in size of the ovary and irregular menstruation occurring after 3-6 months of using the alternate day fasting method (3,4).
A second study looked at menstruation during Ramadan (An Islamic period of fasting, prayer, and reflection in which people fast for 15 or more hours a day for one month). This research revealed that menstrual issues did occur with fasting, with a significant increase in abnormalities when fasting for 15 days or more. Issues had been reduced three months later, but not all were completely resolved (5).
Many medical professionals believe that poor nutrition leads to hormonal disturbances. In recent years, a new term and method of eating based on a woman’s menstrual cycle was developed called “cycle syncing.” Although there isn’t much scientific backing for cycle syncing, there are many anecdotal reports of it providing benefits (6).
Different levels of estrogen, progesterone, and testosterone occur during the cycle with additional nutritional requirements. Understanding your menstrual cycle, paying attention to how you feel, and knowing what your body needs in each phase of the month helps you to feel great all the time and not be at the mercy of hormonal changes. Focusing on whole, healthy foods throughout the cycle is essential for hormonal balance and intermittent fasting success.
1) When menstruating, keep your body hydrated. Eat water-filled foods like cucumbers and melons. Iron levels decrease during this time, so fill up on spinach, apples, and legumes. Avoid red meat when you have your period. Although it is high in iron it is also high in prostaglandins. Prostaglandins levels are already increased during menstruation. They start the uterine contractions and the shedding of the uterine wall leading to menstrual bleeding. Too high levels of prostaglandins in the body cause cramping. Soothe cramps with ginger or chamomile or peppermint tea which you can have when fasting. Reduce or eliminate alcohol, fatty foods, caffeine, and salty foods. Shorter fasts are recommended. When the period ends, increased protein is needed. Eat more eggs, meat, and lentils.
2) During the follicular phase, you can do mid-length fasts depending on your energy level. Focus on foods that increase estrogen production, such as fermented foods, sprouts, kimchi, and sauerkraut. Leafy green vegetables are important. Also, foods called “phytoestrogens” (naturally occurring plant-based estrogens) include flaxseed, pumpkin seeds, and soybeans. Increase your antioxidants and fiber in this phase.
3) In the ovulatory phase, your estrogen and energy levels are at their highest. You can do longer fasts in this phase. Focus on foods that support your liver. Choose fruits, vegetables, and nuts. Limit refined sugar and carbohydrates. If you want to do a 1-3 day prolonged fast, this would be the best time.
4) The luteal phase is directly before bleeding occurs. The body is preparing for another round of ovulation and menstruation, and the fast length should be decreased again. Eliminate foods that may be cramp-inducing such as caffeine, dairy, red meats, carbonated drinks, and artificial sweeteners. Eat foods that increase serotonin levels, are magnesium-rich, and improve general mood. Dark chocolate, quinoa, bananas, tofu, and leafy greens are good choices.
Due to the monthly hormonal changes a woman encounters with menstruation, she needs to pay close attention to how her body reacts to reducing and restricting calories during intermittent fasting. Fasting may cause hormonal interference, exacerbating already occurring problems.
Fast lengths of 12-16 hours are usually beneficial during the entire menstrual cycle, but prolonged fasts should be avoided during your period. Food choices can also play a role in hormonal disruptions. Try cycle syncing and eat according to the phase of your menstrual cycle for maximum hormonal support.
Don’t feel alone as you navigate intermittent fasting and menstruation. Join our online intermittent fasting community of women for support.
1. Grandi G, Ferrari S, Xholli A, et al. Prevalence of menstrual pain in young women: what is dysmenorrhea?. J Pain Res. 2012;5:169-174. doi:10.2147/JPR.S30602
2. Meczekalski, B., Katulski, K., Czyzyk, A. et al. Functional hypothalamic amenorrhea and its influence on women’s health. J Endocrinol Invest 37, 1049–1056 (2014). https://doi.org/10.1007/s40618-014-0169-3
3. Martin B, Pearson M, Kebejian L, et al. Sex-dependent metabolic, neuroendocrine, and cognitive responses to dietary energy restriction and excess. Endocrinology. 2007;148(9):4318-4333. doi:10.1210/en.2007-0161
4. Kumar S, Kaur G. Intermittent fasting dietary restriction regimen negatively influences reproduction in young rats: a study of hypothalamo-hypophysial-gonadal axis. PLoS One. 2013;8(1):e52416. doi:10.1371/journal.pone.0052416
5. Yavangi M, Amirzargar MA, Amirzargar N, Dadashpour M. Does Ramadan fasting has any effects on menstrual cycles?. Iran J Reprod Med. 2013;11(2):145-150.
6. Shah MD, A. I’m So Effing Tired: A Proven Plan To Beat Burnout, Boost Your Energy And Reclaim Your Life. Houghton Mifflin Harcourt; 2021.
7. Vitti, A. WomanCode: Perfect Your Cycle, Amplify Your Fertility, Supercharge Your Sex Drive and Become a Power. HarperOne; 2014.
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