Does Intermittent Fasting Help Irregular Periods in PCOS?: What the Research Shows

Does Intermittent Fasting Help Irregular Periods in PCOS?: What the Research Shows

This trial tested eating only within an 8-hour window each day. It studied 15 women with PCOS who were not having regular periods. After 5 weeks, periods became regular again in about 7 out of 10 women. Body fat went down, and a hormone linked to acne also dropped. It was a small study, so bigger trials are still needed.

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: Eating only within an 8-hour window each day, in women with PCOS who were not having regular periods.
• Who did it: Li and colleagues at Shengjing Hospital of China Medical University, published in the Journal of Translational Medicine in 2021.
• How many people: 18 women signed up, 15 finished, all in their twenties or early thirties (ages 18 to 31).
• How long: 6 weeks total — 1 week of normal eating, then 5 weeks of the 8-hour eating plan.
• What happened: Periods became regular again in about 7 out of 10 women.
• Read the study yourself: Journal of Translational Medicine 2021 →

What They Wanted to Find Out

PCOS stands for polycystic ovary syndrome. It is a hormone condition. It can stop a woman's ovaries releasing an egg, so periods become irregular or stop. Researchers wanted to know if eating only within an 8-hour window each day could help.

This is one study inside a bigger group of trials on fasting and PCOS ovulation. It also connects to newer work on fasting and menstrual regularity in PCOS.

Who Was in the Study

Who they were: All 15 women who finished were between 18 and 31 years old. All of them had PCOS. None were ovulating regularly, which is why their periods were irregular or missing.

What the fasting actually looked like: They ate all their food within an 8-hour window each day. The study does not say which exact hours. It also does not say what drinks were allowed outside that window.

What Happened

Most women's periods became more regular after the fasting weeks.

• Periods became regular again in about 7 out of 10 women (11 of 15).
• Body weight and body fat both went down.
• A hormone linked to acne and extra hair growth went down.
• Insulin levels dropped, meaning their bodies handled sugar better.
• A blood test for body-wide swelling also improved.

What Did Not Change

• The study did not report on muscle loss or muscle changes.
• Not stated in the abstract for cholesterol or blood pressure changes.
• Not stated in the abstract for how long the period changes lasted after the study ended.

What the Researchers Said

The researchers said this eating plan may help women with PCOS. They pointed to weight loss, less body fat, and more regular periods as the main gains.

What This Means for You

• If you have PCOS and irregular periods: this small study found periods became more regular in most women after 5 weeks of the 8-hour eating plan.
• If you are worried about hormones: the hormone linked to acne and extra hair growth went down in this study.
• If you are watching your weight: body fat dropped alongside the period changes, though the study cannot say which change caused the other.
• For women specifically: this study was done only in women with PCOS, so it cannot tell us if the same happens in women without PCOS. See more on fasting and PCOS hormone levels.
• Before you try it: talk to your doctor first, especially if you take medication for PCOS or diabetes.
• Curious about other angles: read about fasting and PCOS weight management.

What This Study Could Not Tell Us

• Only 15 women finished the study — that is a small number.
• All participants were women with PCOS aged 18 to 31, so results may not apply to older women.
• The study ran for only 6 weeks in total, so it cannot say what happens over a year.
• There was no separate comparison group who ate on a normal schedule the whole time.
• Menstrual cycle changes were tracked by the women themselves, not measured in a lab.
• Not stated in the abstract who funded the study.

The Study Details

Li C, Xing C, Zhang J, Zhao H, Shi W, He B. (2021). Eight-hour time-restricted feeding improves endocrine and metabolic profiles in women with anovulatory polycystic ovary syndrome. Journal of Translational Medicine. PMID: 33849562

Common Questions

Can I fast during my period if I have PCOS?

This study did not fast women during their period specifically. It tested a daily 8-hour eating window over 5 weeks and found periods became more regular in most women.

Does intermittent fasting fix irregular periods?

In this small study, about 7 out of 10 women with PCOS saw their periods become more regular. It is not proof it works for everyone, and it was not tested in women without PCOS.

How many women were in this fasting study?

18 women signed up and 15 finished the full 6 weeks. All had PCOS and were not ovulating regularly.

How long did the women fast each day?

They ate all their food within an 8-hour window each day, for 5 weeks after a 1-week starting period.

Did the women lose weight during the study?

Yes, body weight and body fat both went down over the 5 weeks of the 8-hour eating window.

More Research Like This

• 8-Hour Time-Restricted Eating and Insulin in PCOS
• 5:2 Fasting and Menstrual Regularity in PCOS
• Fasting and Hormone Profiles in Women With PCOS
• Time-Restricted Eating for PCOS Weight Loss
• Time-Restricted Eating and Metabolic Health in PCOS
• Fasting Plus Calorie Cutting for PCOS
• Early vs Late Eating Windows in PCOS

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