Intermittent fasting can be a reasonable option for many healthy adult women, and the same schedules used in research, such as 16:8 time-restricted eating and the 5:2 diet, apply to women as well as men. Research on women's hormones and fasting is still limited, so a gentle start and attention to how your body responds matter. It is not advised during pregnancy or breastfeeding, and women with a history of an eating disorder or who take glucose-lowering medicine should get professional advice first.
Key Takeaways
- Fasting schedules are the same for women and men; start gently with a 12-hour overnight fast and move to 14:10 or 16:8 only if it feels right.
- A 2022 review of human studies found no change in estrogen, LH, FSH or prolactin with fasting, but the studies were few, small and short.
- No fasting studies have been done in women around or after menopause, so effects in those years are unknown.
- Trials that enrolled mostly women found weight loss similar to cutting calories every day.
- Pregnancy and breastfeeding raise calorie and iron needs, so this is not a time to fast.
- If fasting leads to preoccupation with food, bingeing or restricting more than you meant to, stop and talk to a professional.
Evidence grade: Emerging. Weight trials that enrolled mostly women show results similar to daily calorie restriction, but research on women's hormones and cycles consists of a few small, short studies in premenopausal women, with none in women around or after menopause.
What Intermittent Fasting Means for Women
Intermittent fasting is an eating pattern that alternates planned periods of eating with periods of fasting or very low calorie intake. It focuses on when you eat rather than on specific foods. The main approaches are the same for everyone: time-restricted eating, the 5:2 diet and alternate-day fasting.
What differs for women is mostly life stage: the menstrual cycle, pregnancy and breastfeeding, and the years around menopause. On several of these, the research is thin, and it is better to say so plainly than to fill the gap with guesswork. For the general evidence on fasting, see our overview of the benefits of intermittent fasting; this page covers what is specific to women.
Common Schedules Women Use
| Method | How it works | Who it tends to suit |
|---|---|---|
| 12-hour overnight fast | For example, 7 p.m. to 7 a.m. | A starting point for almost anyone |
| 14:10 time-restricted eating | Fast 14 hours, eat within a 10-hour window (for example, 9 a.m. to 7 p.m.) | Beginners; women who want a gentle routine |
| 16:8 time-restricted eating | Fast 16 hours, eat within an 8-hour window (for example, 11 a.m. to 7 p.m.) | Women comfortable skipping an early breakfast |
| 5:2 diet | Two low-calorie days a week, five days of usual eating; one trial in women used about 650 kcal on low days | Women who prefer flexible days over a daily rule |
| Alternate-day fasting | Low-calorie "fast days" alternate with usual days | The most demanding option; dropout was highest with it in a one-year trial |
A 24-trial meta-analysis found that intermittent fasting overall produced weight loss similar to ordinary calorie restriction, so there is no need to choose the most extreme version. Pick the schedule that fits your routine, sleep and family life.
What Research Says About Hormones and Cycles
A common worry is that fasting will disrupt women's hormones. Much of that worry traces back to a rodent study; the authors of a 2022 review of human trials note that the female rats were very young, roughly equivalent to a 9-year-old girl. Their summary of the human evidence:
- Estrogen, gonadotropins and prolactin: fasting did not change estrogen, LH, FSH or prolactin in the women studied. Only one clinical trial measured LH and FSH.
- Androgens and SHBG: in premenopausal women with a higher body weight, fasting lowered testosterone and the free androgen index and raised sex hormone-binding globulin (SHBG). This was more likely when all food was eaten before about 4 p.m.
- Big gaps: the human studies were few, small and short, and all were in premenopausal women. It was unclear whether the day of the menstrual cycle was recorded and standardized, and no studies had been done in perimenopausal or postmenopausal women.
The androgen findings are why researchers are interested in fasting for women with polycystic ovary syndrome, but the review frames that as a question for future studies, not an established approach. Anyone with that diagnosis should plan any fasting with their healthcare provider. For more on how hormones and nutrition interact, see our article on hormonal effects on nutrient metabolism.
What this means in practice: current human studies do not show that moderate fasting disrupts the main reproductive hormones, but they do not cover lean, very active or older women well. If your periods become irregular, stop, or change noticeably after you start fasting, stop fasting and talk to your doctor.
Perimenopause and Menopause
The 2022 hormone review found no fasting studies in perimenopausal or postmenopausal women. One small trial in women with a higher body weight (average age 50) compared 8 weeks of fasting with daily calorie restriction and found no difference between groups in hunger, mood, sleep quality or quality of life, but it was not designed around menopause. If you are in this stage of life and interested in fasting, talk with your doctor or a registered dietitian first, particularly if sleep, mood or energy are already affected.
What the Evidence Shows for Weight
Several of the best-known fasting trials enrolled mostly women, and they tell a consistent story: fasting works about as well as ordinary calorie reduction, not better.
- In a 6-month trial of 107 premenopausal women, two low-calorie days a week led to an average loss of 6.4 kg versus 5.6 kg with daily restriction, not a significant difference.
- In a one-year trial of 100 adults, 86 of them women, alternate-day fasting and daily calorie restriction produced similar weight loss, and more people dropped out of the fasting group (38% vs 29%).
- In the 8-week trial of 46 women mentioned above, the fasting group lost more weight, with no difference in eating behaviors or mood, but the trial was short.
So the main reason to choose intermittent fasting is that it suits you. Some women find a clear eating window easier than counting calories; others find it makes them irritable or overly focused on food. Our article on intermittent fasting for weight loss goes into the trial results in more detail.
Eating Well Within Your Window
A shorter window leaves fewer meals to cover your nutrient needs. Iron is a good example: the NIH recommends 18 mg a day for women aged 19 to 50, compared with 8 mg for men of the same age and for adults over 50. Within your window, aim for:
- Protein at every meal: eggs, Greek yogurt, fish, poultry, beans, lentils or tofu.
- Iron and calcium sources: lean meat, seafood, beans, iron-fortified cereals, dairy or fortified alternatives and leafy greens. Our guide to the role of iron in energy levels lists more options.
- Vegetables, fruit and whole grains for fiber and nutrients.
- Healthy fats such as olive oil, nuts, seeds and avocado.
- Fluids during fasting hours: water, sparkling water, black coffee or unsweetened tea.
Here is a simple 14:10 day:
| Time | What to have |
|---|---|
| Before 9:00 a.m. (fasting) | Water, black coffee or unsweetened tea |
| 9:00 a.m. | Oatmeal with milk or fortified soy milk, berries and walnuts |
| 1:00 p.m. | Lentil or chicken soup with a side salad and whole-grain bread |
| 4:00 p.m. | Greek yogurt or cottage cheese with fruit |
| 6:30 p.m. | Salmon or tofu with roasted vegetables and brown rice; finish by 7:00 p.m. |
How to Start Gently
- Begin with a 12-hour overnight fast, such as 7 p.m. to 7 a.m.
- After a week or two, move to 14:10 if you feel well.
- Try 16:8 only if 14:10 is comfortable and fits your life.
- Keep your eating window consistent on the days you fast.
- Track sleep, mood, energy and your cycle, and step back if things get worse.
Safety and Interactions
- Pregnancy. Calorie needs do not usually rise in the first trimester, but the Dietary Guidelines for Americans estimate about 340 extra calories a day in the second trimester and 452 in the third, and the iron recommendation rises to 27 mg a day. Fasting is not a good fit for this time; follow your prenatal care provider's guidance. Women trying to conceive should also discuss fasting with their doctor.
- Breastfeeding. The same guidelines estimate about 330 extra calories a day in the first 6 months of breastfeeding and about 400 in the second 6 months. See our breastfeeding diet guide for eating well during this time.
- Eating disorder history. In a survey of 2,762 Canadian adolescents and young adults, intermittent fasting was linked with more eating disorder symptoms, and the links with eating disorder behaviors were most consistent in young women. A survey cannot prove fasting causes these problems, but if you have a current or past eating disorder, do not fast without guidance from your treatment team.
- Girls and young women under 18 are still growing; the fasting trials discussed here enrolled adults.
- Glucose-lowering medicines. A clinical review identifies low blood sugar as the most immediate fasting risk for people taking insulin or sulfonylureas; talk to your doctor before fasting if you take either, as doses may need adjusting.
- Medicines taken with food. Ask your doctor or pharmacist how a fasting window fits around any medicine that must be taken with a meal.
Stop fasting and seek help if you feel dizzy or faint, your periods change, or fasting leads to bingeing or restricting more than you intended.
Frequently Asked Questions
Is intermittent fasting safe for women?
For many healthy adult women, moderate fasting such as 14:10 or 16:8 appears reasonable. It is not advised during pregnancy or breastfeeding, for girls under 18, or without professional guidance for women with a history of an eating disorder or who take glucose-lowering medicine.
Does intermittent fasting affect a woman's menstrual cycle?
Research is limited. A 2022 review of human trials found no change in estrogen, LH or FSH in the women studied, but those studies were few, small and short, and cycle timing was not consistently recorded. If your periods change after you start fasting, stop and talk to your doctor.
What is the best intermittent fasting schedule for women?
Many women start with a 12-hour overnight fast and move to 14:10 or 16:8. Studies have not found one method clearly better for weight, so the best schedule is the one you can follow comfortably and safely.
Should women fast during perimenopause or menopause?
No fasting studies have been done specifically in women around or after menopause, so the effects are unknown. Talk to your doctor or a registered dietitian before trying it.
Can I do intermittent fasting while breastfeeding?
It is not a good time to fast. Breastfeeding raises calorie needs by about 330 to 400 calories a day, so focus on regular, balanced meals and talk to your doctor or a registered dietitian about your needs.
Is intermittent fasting better than a regular diet for women's weight loss?
Trials that enrolled mostly women found weight loss similar to ordinary daily calorie reduction. Fasting can be a useful structure if it suits you, but it is not more effective on its own.
Sources
- Cienfuegos S, Corapi S, Gabel K, et al. Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials. Nutrients. 2022.
- Harvie MN, Pegington M, Mattson MP, et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. International Journal of Obesity. 2011.
- Trepanowski JF, Kroeger CM, Barnosky A, et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Internal Medicine. 2017.
- Teong XT, Hutchison AT, Liu B, et al. Eight weeks of intermittent fasting versus calorie restriction does not alter eating behaviors, mood, sleep quality, quality of life and cognitive performance in women with overweight. Nutrition Research. 2021.
- Elortegui Pascual P, Rolands MR, Eldridge AL, et al. A meta-analysis comparing the effectiveness of alternate day fasting, the 5:2 diet, and time-restricted eating for weight loss. Obesity. 2023.
- Ganson KT, Cuccolo K, Hallward L, Nagata JM. Intermittent fasting: Describing engagement and associations with eating disorder behaviors and psychopathology among Canadian adolescents and young adults. Eating Behaviors. 2022.
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 2020.
- NIH Office of Dietary Supplements. Iron: Fact Sheet for Consumers.
- Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019.
Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.
Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: · How OPA researches and writes
