Intermittent Fasting Trial in Women with PCOS

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Intermittent fasting trial in women with PCOS


In this trial, daily intermittent fasting (4pm to 8am) among overweight women with PCOS, for a period of 5 weeks significantly reduced mean body fat mass (35.28 to 32.89 kg), insulin levels (15.60 to 12.30 μU/mL) and total testosterone (-0.09 ng/mL) leading to improved menstrual cycles (11/15).


The current International Evidence based Guideline for the Assessment and Management of PCOS recommends dietary and exercise interventions as primary management strategies.

A variety of diets such as the low glycemic index (GI) diet, dietary approaches to stop hypertension (DASH) diet, Mediterranean diet, low carbohydrate diet, pulse-based diet, ketogenic diet, low-starch/low-dairy diet and vegetarian diet have all been proposed. 

On the other hand, intermittent fasting which is the general term for 3 new types of diets: alternate-day fasting, 5:2 diet, and time-restricted feeding (TRF), is reported to help with losing weight, improve insulin resistance, regulate metabolism and enhance cardiometabolic health.

However other than a limited study of Muslim women with PCOS fasting during Ramadan, there has been no specific studies investigating the potential impact of intermittent fasting on women with PCOS.


To explore the effects of time-restricted feeding on menstruation, gonadal and metabolic parameters in women with anovulatory PCOS.


Women aged 18 to 40 with PCOS (Rotterdam criteria), BMI ≥ 24 kg/m2 and anovulation were recruited from the Department of Endocrinology, Shengjing Hospital of China Medical University. 

Any woman matching the following conditions was automatically excluded from the trial to minimise potential bias:

  • Use of any medication (or Fish Oil) which effects carbohydrate/lipid metabolism in the last 6 months
  • More than 5% change in body weight in the last 3 months
  • Preparing for pregnancy, pregnant or lactating
  • Perimenopausal
  • Night-shift workers
  • Alcohol > 100g/week or smoking
  • Fasting >16hr/day
  • High-intensity exercise
  • Hypertensive
  • Other pre-existing conditions (congenital adrenal hyperplasia, Cushing syndrome, androgen-secreting tumors, hyperprolactinemia, diabetes, thyroid diseases, cardiovascular, gastrointestinal, kidney and liver diseases)

The trial itself began with a 1-week baseline weight stabilisation period, followed by a 5-week TRF intervention where women were asked not to change the composition of their diet, but eat freely from 8am to 4pm, and then fast between 4pm to 8am.

Daily food intake was recorded from start to finish using Boohee, a diet and fitness app, to calculate corresponding calories and maintain intake within 10% of baseline. Water and calorie free beverages were allowed during the 16 hour fast.

Before and after measurements included:

  • weight, height, BMI, Waist-to-Hip Ratio (WHR), skeletal muscle mass (SMM), body fat mass (BFM), body fat percentage (BF%), visceral fat area (VFA)
  • luteinizing hormone (LH), follicle-stimulating hormone (FSH), total testosterone (TT), sex hormone-binding globulin (SHBG)
  • total cholesterol (TC), triglycerides (TG), low density lipoprotein-cholesterol (LDL-C)
  • alanine aminotransferase (ALT), aspartate aminotransferase (AST), uric acid (UA), insulin-like growth factor 1 (IGF-1), glucose and high-sensitivity C-reactive protein (hs-CRP)

Similarly, TFEQ-R21 questionnaires were completed during pre and post-trial visits. This questionnaire covers the 3 eating behaviour domains: cognitive restraint scale; emotional eating scale and uncontrolled eating scale to capture any changes in eating behaviour during the study.


Following initial assessment of 25 women with PCOS, a total of 18 women who satisfied the inclusion and exclusion criteria were enrolled in the study. Three women could not be contacted after the first week, reducing the final study size to 15 women, aged 18 to 31, mainly insulin resistant (HOMA-IR > 2.3) and anovulatory (menstrual cycle delayed by 3 months to 3 years).

During the study, feeling hungry every day was reported by 2 women (13.3%), several days per week by 3 women (20.0%), once a week or less by 7 women (46.7%), and never by three women (20.0%). Overall 7 women (46.7%) found it easy to adhere to the TRF rules, while six (40.0%) found it neither easy nor difficult, and 2 women (2/15, 13.3%) found it difficult.

Initial anthropometric and body composition measurements showed women lost an average 1.3 kg weight during the trial with statistically significant reductions in BMI, BFM (35.3 to 32.9 kg), BF% (40.7 to 39.7 %) and VFA (164.8 to 154.7 cm2).

Metabolic improvements included fasting insulin levels (15.60 to 12.30 μU/mL), HOMA-IR and area under the curve (AUC) for insulin. 

Similarly, menstrual cycle irregularity improved in 73.3% (11/15) of women while gonadal parameters, specifically SHBG increased (19.00 to 22.70 nmol/L), while TT (1.00 to 0.91 ng/mL) and FAI decreased.

Interestingly LH decreased moderately (13.09 to 10.67 mIU/mL), although this was not statistically significant (P= 0.176), with no real change in FSH observed.

Finally a significant decrease in hsCRP and ALT level was noted, while IGF-1 levels increased, pointing to reduced inflammation and insulin sensitivity.

Analysis of TFEQ-R21 questionnaires confirmed cognitive restraint, uncontrolled eating and emotional eating did not change over the trial period.


  1. Small study size.
  2. Short study duration.
  3. No control group.


This trial was supported the National Natural Science Foundation of China and the “345 Talent Project”.


Failure to ovulate.

Proportional measurements of the human body.

Related to gonads.

Fats in the bloodstream (i.e. cholesterol, triglycerides).

The time leading up menopause.

Similar studies

Harris L, et al. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis.

Asemi Z, et al. (2015). Effects of Ramadan Fasting on Glucose Homeostasis, Lipid Profiles, Inflammation and Oxidative Stress in Women with Polycystic Ovary Syndrome in Kashan, Iran.

Fauser B C, et al. (2012). Consensus on women’s health aspects of polycystic ovary syndrome (PCOS): the Amsterdam ESHRE/ASRM-Sponsored 3rd PCOS Consensus Workshop Group.

Booth P J, et al. (1996). Endocrine and metabolic responses to realimentation in feed-restricted prepubertal gilts: associations among gonadotropins, metabolic hormones, glucose, and uteroovarian development.


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