Intermittent Fasting and Fertility: What the Research Shows

Intermittent Fasting and Fertility: What the Research Shows

Researchers tested a 5:2 fasting plan on 90 women with PCOS, a hormone condition that affects periods and fertility. Women ate normally five days a week and cut calories sharply on two days. After 12 weeks, 8 out of 10 women had more regular periods. Half of them ovulated more often too.

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: a 5:2 fasting plan — eating normally 5 days and cutting calories sharply on 2 days — in women with PCOS.
• Who did it: An and colleagues at Beijing Haidian Hospital, published in Frontiers in Endocrinology in 2026.
• How many people: 90 women, all with PCOS and extra body weight. Exact ages: Not stated in the abstract.
• How long: 12 weeks.
• What happened: the main fasting group lost about 8 kilos. 8 out of 10 women got more regular periods.
• Read the study yourself: Frontiers in Endocrinology 2026 →

What They Wanted to Find Out

PCOS (polycystic ovary syndrome) is a hormone condition. It can cause irregular periods. It can also make it harder to get pregnant.

PCOS is often linked to extra body weight. It is also linked to trouble handling blood sugar. Doctors wanted to know if a simple fasting pattern could help.

They tested the 5:2 plan. That means normal eating most days, low calories on two days a week. They checked weight, blood sugar, and signs of fertility like period regularity and ovulation.

This study sits next to other PCOS fasting work. See the study on period regularity in PCOS. See also the study on hormone changes in PCOS.

Who Was in the Study

Who they were: All 90 women had PCOS. All of them were carrying extra weight. The abstract does not give their exact ages.

What the fasting actually looked like: On 2 days each week, women cut calories sharply. One group used meal-replacement shakes on those days. The other fasting group ate normal lower-calorie meals on those same days. On the other 5 days, everyone ate as usual.

What Happened

Women who fasted with meal-replacement shakes lost the most weight. Their periods also changed the most.

• Waist size went down in the fasting-plus-shakes group.
• Body size scores also went down in that group.
• A test for how the body handles the sugar hormone insulin got better.
• Blood sugar measured two hours after eating also dropped.
• About half of the main fasting group ovulated more often than before.
• Fertility hormone levels did not change much in either fasting group.

What Did Not Change

• Fertility hormone levels stayed about the same in both fasting groups.
• Muscle was not measured in this study, so it cannot say either way.

What the Researchers Said

The team said 5:2 fasting with shakes helped women with PCOS lose weight. They said it may also support more regular periods and ovulation. They called for bigger, longer studies to confirm the fertility hormone picture.

What This Means for You

• If you have PCOS: this small study suggests 5:2 fasting may help with weight and period regularity.
• Shakes may matter: women using shakes on fasting days did better than those eating regular food those days.
• Don't expect a hormone fix: key fertility hormones like estrogen and progesterone did not shift much here.
• If you're trying to conceive: more regular ovulation is encouraging. This study did not track actual pregnancies.
• For more on fertility and fasting: see how fasting affected egg supply and fertility hormones.
• For more on PCOS: another trial found fasting helped weight and hormone levels too.

What This Study Could Not Tell Us

• It ran for only 12 weeks. It cannot say what happens after that.
• All 90 women had PCOS and extra weight. Results may not apply to other women.
• Women were not placed into groups by chance. This can affect fairness of comparison.
• The study did not track whether any woman became pregnant.
• Funding: 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

Does intermittent fasting improve fertility in women?

This study did not measure pregnancy directly. It found that 8 out of 10 women with PCOS had more regular periods. This was after 12 weeks of 5:2 fasting with shakes.

Can fasting help with PCOS periods?

Yes, in this study it did. Periods became regular in most women in the fasting-plus-shakes group. Half of them also ovulated more often.

Does fasting change fertility hormones like estrogen?

Not much, based on this study. Estrogen, progesterone, and two other fertility-related hormones stayed about the same in both fasting groups.

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

Women in the main fasting group went from about 77 kilos to about 69 kilos. That is roughly 8 kilos in 12 weeks.

Is 5:2 fasting safe for women trying to get pregnant?

This study did not test pregnancy outcomes directly. Talk to your doctor before trying any fasting pattern if you are trying to conceive.

More Research Like This

• 5:2 Fasting Improved Menstrual Regularity in 80% of Obese Women With PCOS
• Intermittent Fasting Reduces Insulin Resistance and Improves Hormone Profiles in Women with PCOS
• Intermittent Fasting and Ovarian Reserve in Women
• Time-Restricted Eating Helped Women With PCOS Lose Weight
• Time-Restricted Eating for PCOS
• 8-Hour Time-Restricted Eating Improved Insulin and Hormone Levels in Women With PCOS
• Early Time-Restricted Eating Helped Women With PCOS Most

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