Fasting and Fertility in Women With PCOS: What the Research Shows

Fasting and Fertility in Women With PCOS: What the Research Shows

A 2026 study tested a 5:2 fasting diet in 90 women with PCOS, a hormone condition that can make periods and ovulation irregular. After 12 weeks, 8 out of 10 women on the fasting plan had regular periods again, and half started ovulating more often. Their main reproductive hormones did not change.

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

The Short Version

• What they tested: Whether a 5:2 fasting diet helps periods and ovulation in women with PCOS, a hormone condition linked to fertility trouble.
• Who did it: Lead researcher W. An at Beijing Haidian Hospital, part of Peking University Third Hospital, China, published in Frontiers in Endocrinology in 2026.
• How many people: 90 women, all with PCOS and extra body weight. Age range: Not stated in the abstract.
• How long: 12 weeks.
• What happened: Periods became regular in 8 out of 10 women, and half started ovulating more often.
• Read the study yourself: Frontiers in Endocrinology 2026 →

What They Wanted to Find Out

PCOS (a hormone condition that makes periods and ovulation irregular) can make it harder to get pregnant. Extra body weight often makes PCOS symptoms worse. Researchers wanted to know if a simple eating pattern could help. They tested the 5:2 diet, normal eating five days and very low calories two days. Could it bring back regular periods and ovulation?

This question matters beyond one study. You can read more on intermittent fasting and PCOS hormones and fasting and ovulation timing in PCOS.

Who Was in the Study

Who they were: All 90 women had PCOS and were carrying extra weight. Age range is not stated in the abstract. The study does not say how many finished all 12 weeks.

What the fasting actually looked like: On fasting days, one group drank a single low-calorie shake instead of regular meals. The other fasting group ate low-calorie food on those same two days. Both groups ate as usual the other five days of the week.

What Happened

Periods became regular again in 8 out of 10 women following the fasting plan with meal-replacement shakes.

• Women on the meal-replacement fasting plan lost about 8 kilos over 12 weeks.
• Their waist size and body size measurements also went down.
• Blood sugar levels taken two hours after eating got better.
• The body handled insulin better, though no plain number was given.
• Main reproductive hormones — including estrogen and two hormones that control the ovaries — stayed about the same.

What Did Not Change

• The main female hormones — estrogen, progesterone, and two others that control ovulation — showed no clear change.
• The abstract does not mention muscle at all, so it cannot say whether anyone lost muscle.

What the Researchers Said

The researchers said the fasting plan with meal-replacement shakes helped women lose weight. They said periods and ovulation improved even though hormone blood tests stayed flat.

What This Means for You

• If you have PCOS and irregular periods: this study suggests a 5:2 fasting pattern may help periods return, though it is not proof it will work for everyone.
• For women specifically: every participant here was a woman, so these results come directly from female bodies, not guessed from men.
• Meal replacement may matter: the group using shakes on fasting days did better than the group eating regular low-calorie food.
• Hormones did not shift: if you were hoping for a hormone-level change, this study did not find one.
• It is not a fertility trial: the study tracked periods and ovulation, not actual pregnancies.
• Talk to your doctor first, especially since PCOS treatment plans vary a lot between women. You can also read how time-restricted eating affected PCOS weight and 8-hour eating and PCOS hormones.

What This Study Could Not Tell Us

• People were not randomly assigned to groups, so other factors could explain some results.
• The abstract does not say how many women were in each of the three groups.
• Age range of participants is not stated in the abstract.
• It ran for only 12 weeks, so it cannot say what happens after a year.
• It tracked periods and ovulation, not whether more women actually became pregnant.
• Funding source is not reported in the abstract.

The Study Details

An, W., Chen, F., Wang, B., Zhou, S., Jiang, L., An, B., et al. (2026). Effect of a 5:2 intermittent fasting diet on obese patients with polycystic ovary syndrome. Frontiers in Endocrinology. PMID: 41928885

Common Questions

Is fasting good for fertility in women with PCOS?

This study found better periods and more ovulation after 12 weeks of 5:2 fasting. It did not measure pregnancy rates, so it cannot say fasting improves fertility directly.

How much weight did women lose with 5:2 fasting?

Women on the meal-replacement fasting plan lost about 8 kilos over 12 weeks. The group without meal replacement improved less, but exact numbers are not stated in the abstract.

Did fasting change hormone levels in this study?

No. The main reproductive hormones, including estrogen and two hormones that control the ovaries, stayed about the same in all groups.

How many women got their periods back on track?

Eight out of ten women on the meal-replacement fasting plan had regular periods again after 12 weeks.

Does this study prove fasting helps you get pregnant?

No. It only tracked periods and ovulation, not actual pregnancies, and people were not randomly assigned to groups.

More Research Like This

• 5:2 Intermittent Fasting Improved Menstrual Regularity in 80% of Obese Women With PCOS
• Intermittent Fasting Reduces Insulin Resistance and Improves Hormone Profiles in Women with PCOS
• 8-Hour Time-Restricted Eating Improved Insulin and Hormone Levels in Women With PCOS
• Time-Restricted Eating Helped Women With PCOS Lose Weight
• Early Time-Restricted Eating Helped Women With PCOS Most
• Intermittent Fasting and Ovarian Reserve in Women
• Does Time-Restricted Eating Change Women's Hormones? No

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