Fasting Didn't Beat Calorie Cutting for Inflammation in PCOS: What the Research Shows

Fasting Didn't Beat Calorie Cutting for Inflammation in PCOS: What the Research Shows

Researchers tested two fasting plans against calorie cutting in 90 women with PCOS. One fasting group also took a probiotic pill. After 8 weeks, inflammation went down in all three groups. Fasting did not work better than simply cutting calories. The 2025 trial came from Tehran University of Medical Sciences.

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 plan, especially if you have an existing health condition or take medication.

The Short Version

• What they tested: Whether eating only within a 10-hour window, with or without a probiotic pill, helped more than cutting calories in women with PCOS.
• Who did it: Sahar Talebi and colleagues at Tehran University of Medical Sciences, published in Journal of Research in Medical Sciences in 2025.
• How many people: 90 women with PCOS, all carrying extra weight, average age about 30.
• How long: 8 weeks.
• What happened: Signs of inflammation went down in all three groups, but fasting did not beat calorie cutting.
• Read the study yourself: J Res Med Sci 2025 →

What They Wanted to Find Out

PCOS (polycystic ovary syndrome) often comes with extra body weight and ongoing inflammation. Researchers wanted to know if eating only during a 10-hour window each day — and fasting the other 14 hours — could ease that inflammation better than simply cutting calories. They also wanted to see if adding a probiotic pill to the fasting plan made it work even better. This matters because many women with PCOS are told to "just eat less," and this study asked if timing eating hours could do more.

If you want more background on PCOS and fasting, see Intermittent Fasting and Ovarian Reserve in Women and 8-Hour Time-Restricted Eating and PCOS Hormones.

Who Was in the Study

Who they were: All 90 women had PCOS and were carrying extra weight. Their average age was about 30 years old. Their average weight at the start was about 81 kilograms.

What the fasting actually looked like: The two fasting groups ate all their food within a 10-hour window early in the day. They fasted for the other 14 hours but could still drink water. They followed this plan every day for 8 weeks.

What Happened

All three groups showed less inflammation after 8 weeks, but fasting did not work better than cutting calories.

• A blood test for inflammation went down in all three groups by the end of the study.
• A test for the body's defense against cell damage improved in the fasting-plus-probiotic group and in the comparison group.
• Blood pressure dropped slightly in both fasting groups, but only by a tiny amount.
• The researchers found no real difference between the three groups for blood pressure, inflammation, or cell damage markers.
• Adding a probiotic pill to fasting did not clearly beat fasting alone.

What Did Not Change

• There was no difference between the three groups for blood pressure, signs of inflammation, cell damage, or the body's defense against cell damage by the end.
• Muscle: Not stated in the abstract — this study did not report on muscle.

What the Researchers Said

The researchers concluded that eating only during a 10-hour window — with or without a probiotic pill — did not work better than cutting calories. For women with PCOS, cutting calories looked just as helpful as changing eating hours.

What This Means for You

• If you have PCOS: Cutting calories may work just as well as fasting for easing inflammation, based on this trial.
• Probiotics are not a shortcut: Adding a probiotic pill to fasting did not clearly add extra benefit here.
• For women specifically: All 90 participants were women with PCOS, so these findings speak directly to that group, not to everyone.
• Pick what you can stick to: Since all three plans worked about equally well, choose the one that fits your life.
• See also Does Time-Restricted Eating Help PCOS Hormones? and 5:2 Fasting and Menstrual Regularity in PCOS.

What This Study Could Not Tell Us

• It only included 90 women split into three groups, which is a fairly small number.
• Every participant was a woman with PCOS who was carrying extra weight, so results may not apply to other groups.
• It ran for only 8 weeks, so it cannot say what happens over a longer time.
• Some details, like exactly how closely each woman followed her plan, were not fully reported.
• Funding: Not stated in the abstract.

The Study Details

Talebi, S., Shab-Bidar, S., Askari, G., Mohammadi, H., Moini, A., & Djafarian, K. (2025). Comparison of the impact of intermittent fasting diet alone or in conjunction with probiotic supplementation versus calorie-restricted diet on inflammatory, oxidative stress, and antioxidant capacity biomarkers in women with polycystic ovary syndrome: A randomized (people were put into groups at random) placebo (a dummy treatment)-controlled trial. Journal of Research in Medical Sciences. PMID: 40200973

Common Questions

Does intermittent fasting help PCOS inflammation?

In this study, inflammation went down in the fasting groups. But it also went down just as much in the calorie-cutting group. So fasting did not show a clear edge over cutting calories here.

Is time-restricted eating better than calorie counting for PCOS?

No, not in this trial. All three groups of 30 women showed similar results after 8 weeks. Neither fasting plan beat simply eating fewer calories.

Can probiotics boost the benefits of fasting for PCOS?

Adding a probiotic pill to the fasting plan did not clearly add extra benefit in this study. The fasting-plus-probiotic group did see some improvement in one cell-damage test, but so did the calorie-cutting group.

How many women were in this PCOS fasting study?

There were 90 women total, split evenly into three groups of 30 each. All of them had PCOS and were carrying extra weight.

How long did the PCOS fasting study last?

The study ran for 8 weeks. That is long enough to see short-term changes, but too short to know what happens after many months.

More Research Like This

• 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
• 5:2 Intermittent Fasting Improved Menstrual Regularity in 80% of Obese Women With PCOS
• Time-Restricted Eating Helped Women With PCOS Lose Weight
• Time-Restricted Eating for PCOS
• Time-Restricted Eating Helped Women With PCOS Lose More Weight
• Early Time-Restricted Eating Helped Women With PCOS Most

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