Intermittent fasting for PCOS: what does the evidence say?

Within recent years intermittent fasting has become a trendy way to eat. It has been touted to have many positive effects on health but does the evidence support the hype? And what about intermittent fasting for PCOS? Let’s dive into this diet and understand if it is helpful for people living with PCOS. Keep reading!

What is PCOS?

Polycystic ovary syndrome (or polycystic ovarian syndrome) known as PCOS is a hormonal condition impacting approximately 6-13% of people with ovaries worldwide. There are many symptoms of PCOS. Some of the most common PCOS symptoms are irregular periods, oily skin, acne, excess hair growth on the face, and alopecia plus it is linked to an increased risk of certain chronic diseases such as metabolic syndrome.

The cause of PCOS is unknown but it is thought to be linked to environmental factors, genetics and lifestyle factors.

PCOS cannot be cured but symptoms can be managed by medicating, supplementing or making lifestyle changes to your diet, stress management or exercise routine. One diet that is often promoted for PCOS is intermittent fasting. But does intermittent fasting have benefits for PCOS?

What is intermittent fasting?

Intermittent fasting is a pattern of eating that alternates between periods of fasting and periods of eating. It doesn’t involve restricting certain foods or how much food you consume but instead involves time-restricted eating.

There are several types of intermittent fasting including the 16/8 method, the 5:2 diet, the eat-stop-eat method, the alternate-day fasting and the warrior diet. Although primarily it doesn’t directly encourage calorie restriction often caloric intake is restricted because of the reduced time available to eat. This means that intermittent fasting is often linked to weight loss and is used as a weight management technique.

What is the theory behind intermittent fasting for PCOS?

There are many proposed health benefits of intermittent fasting but the evidence for intermittent fasting for PCOS is minimal. Intermittent fasting has been hypothesised to have potential benefits for PCOS by improving insulin levels, reducing chronic inflammation and improving menstrual cycle regularity.

Improve insulin sensitivity

PCOS is associated with insulin resistance. Approximately 80% of people living with PCOS are insulin-resistant. Insulin resistance is a complex metabolic condition where the body’s cells do not respond to insulin in the way we would expect.

High insulin levels contribute to increased androgen production so it is thought that improving insulin sensitivity reduces the risk of insulin resistance and therefore reduces hyperandrogenism. Therefore lowering testosterone levels and reducing symptoms like acne, oily skin, hirsutism and alopecia, for example.

2014 review found that intermittent fasting resulted in similar fasting insulin and insulin resistance improvements as calorie restriction. But this review was not only short term but also had a small number of participants so more research is required – especially in people with PCOS.

2022 systematic review found that people with PCOS undertaking Ramadan fasting had no significant changes in their insulin levels during this fasting period. Of course, more studies are needed to understand the effect of time-restricted feeding on PCOS but these results are not promising.

Reduce chronic inflammation

People with PCOS are thought to have chronic inflammation. Chronic inflammation is associated with conditions such as cardiovascular disease, diabetes, cancer, arthritis, and gastrointestinal disorders such as Crohn’s disease and ulcerative colitis.

study of eighteen people with PCOS and anovulation participated in a six-week trial to measure the impact of intermittent fasting on PCOS biomarkers. Only fifteen people finished the study but they found that significant improvements in inflammatory markers were seen in participants.

Of course, this study is extremely small and more long-term research is required. Plus other ways of eating for PCOS may improve inflammation – and they don’t require fasting!

Regulates hormonal imbalances

PCOS is an endocrine disorder which means it is a hormonal disorder. This means that people with PCOS tend to have high levels of insulin and luteinizing hormone (LH) and low levels of follicle-stimulating hormone (FSH).

study on PCOS mice found that time-restricted feeding (i.e. intermittent fasting) reduced the LH/FSH after eight weeks. Of course, rodent studies should be taken with a pinch of salt and studies with PCOS patients are required to understand the impact of intermittent fasting on hormonal imbalances in people with PCOS.

Does intermittent fasting work for people with PCOS?

The studies on intermittent fasting on PCOS are few and far between. The studies that we do have often have small sample sizes, do not include PCOS sufferers as participants and have mixed results. From this evidence, we cannot conclusively say that intermittent fasting works for people with PCOS. Also, there may be adverse effects to consider for people trying intermittent fasting for PCOS which we discuss below.

Is intermittent fasting safe for people with PCOS?

It is important to be aware of the risks of intermittent fasting, especially in those living with PCOS. Intermittent fasting may increase the risk of eating disorders, insomnia, fatigue, hypoglycemia and hormonal imbalances in people with PCOS.

May increase the risk of eating disorders

Eating disorder risk is higher in people living with PCOS and any form of restriction or micro-managing of the diet may lead to disordered eating behaviours. Intermittent fasting claims that it does not restrict the foods you eat, but being told when to eat is a type of diet.

Here at The PCOS Collective, we encourage intuitive eating for PCOS as it is a way of eating and living that prioritises your mental and physical wellbeing from a place of joyful nourishment, rather than restriction.

May contribute to insomnia and fatigue

People with PCOS already have high levels of insomnia and fatigue. Not eating regularly and allowing your blood sugar levels to rise and fall rapidly from only eating during specific periods of time may contribute to feelings of fatigue. We recommend eating every few hours to support your blood glucose levels and prevent crashes in energy.

​Insomnia may occur if you haven’t eaten enough throughout the day. Your body may be giving you signs to eat which may impact your sleep. Make sure you are eating enough throughout the day to counteract this.

May lead to hypoglycemia

If you are taking insulin sensitiser medications or supplements like metformin, inositol or berberine then it is particularly important to be aware that intermittent fasting could contribute to hypoglycemia. Hypoglycemia is a medical condition where blood glucose levels go abnormally low in the body. Symptoms of hypoglycemia can include shakiness, sweating, fainting, rapid heartbeat, confusion or blurred vision.

If you choose to try intermittent fasting speak to a healthcare professional before starting, particularly if you are consuming any insulin sensitisers.

Considerations if starting intermittent fasting

If you are considering starting intermittent fasting you must understand the side effects of intermittent fasting and it is a good idea to work with a nutrition professional to ensure you are consuming enough macro and micronutrients during your eating window.

Do we recommend intermittent fasting for PCOS?

To put it simply, no. We do not recommend intermittent fasting for PCOS. The evidence we have to support intermittent fasting is of poor quality and restricting in this way may contribute to eating disorders or disordered eating, insomnia, fatigue, hypoglycemia and hormonal imbalances.

Instead, we recommend finding a nourishing, sustainable way of eating that supports your unique symptoms and fits in with your lifestyle.

What is the best diet for PCOS?

Although there is no one “PCOS diet” there are certain ways of eating that may be beneficial for certain symptoms. We recommend eating regularly, combining fats, proteins and carbohydrates in each meal and eating to support your gut microbiome. Learn more about foods for PCOS and how dieting impacts symptoms in our dedicated article.

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Alex Okell ANutr Founder and Editor

Founder and Editor | Registered Associate Nutritionist

  Founder of Be The Collective LTD [The PCOS Collective & The Endo Collective] Alex Okell ANutr is a London-based reproductive health nutritionist with experience in research, private practice and digital media. She holds a Master’s degree in Nutrition from King’s College London and has co-authored papers with the University of Cambridge, King’s College London, The Food Foundation and the Food Standards Agency. Alex offers 1:1 PCOS support in our virtual PCOS clinic.

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