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Intermittent fasting and PCOS: what a nutritionist wants you to know

Intermittent fasting (IF) has been gaining traction in the hormone health space, as a possible strategy to manage polycystic ovary syndrome (PCOS)-related weight gain and lower testosterone levels.

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But, with studies still in their infancy, is IF a viable option for PCOS sufferers, and are there any dangers in practising it?

Intermittent fasting means only consuming food for a short, specific amount of time in a 24 hour period, often people start with 12 hours of fast, and 12 of feed. As diet and lifestyle alteration – under the guidance of a healthcare professional – is the primary treatment plan for people with PCOS and weight gain and hirsutism (excessive body hair growth) are two common symptoms, introducing a pattern that consists of alternating between a feed and fast state is thought to influence insulin, and dampen PCOS symptoms.

Why is insulin significant?

The hormone insulin plays a significant role in PCOS and contributes towards high levels of glucose in the bloodstream. When you eat carbohydrates – both simple and starchy – they’re broken down and moved into the bloodstream as glucose. Insulin is responsible for transferring glucose from the bloodstream into cells to use for energy, but many people with PCOS are resistant to the action of insulin.

If you are insulin resistant, your body won’t be using the insulin count it does have correctly, and the pancreas may then try to produce higher levels of insulin in an effort to keep your blood glucose levels normal. A high level of insulin can impair healthy ovulation and make excess male hormones (androgens), leading to hirsutism.

As eating stimulates insulin, when you reduce the amount of regular stimulation (fasting) you, therefore, reduce blood sugar and insulin levels. In a fasting state, the body moves from storage (of sugar/energy) mode into a fat-burning mode, using up its own storage, resulting in weight loss. Lowering regular insulin levels will also help manage excess androgens.

All people with female reproductive organs produce testosterone from their ovaries, but if you have PCOS, you can produce high levels of the hormone, and insulin stimulates the ovaries to produce testosterone.

So if you have too much insulin, you are likely to be producing an excess of testosterone which disrupts the development of the sacs in your ovaries and can impair healthy menstruation.

Fasting and the facts

The word ‘fast’ scares me – and maybe for good reason – so I put it to Anna Löfgren, a nutritional therapist specialising in female hormone health, to get a fair analysis of the pros and cons of intermittent fasting, in relation to PCOS.

Anna notes that early studies of intermittent fasting have benefits linking to: 

  • improved insulin sensitivity
  • improved cognitive function
  • improved new cell growth
  • increased weight loss and reduced body fat
  • reduced inflammation

On the face of it, the list of suspected benefits do look very promising, but in reality, the practice does have some downsides and should be approached with caution. Anna says, “A 2005 study by Obesity Research concluded that while IF improved insulin sensitivity in men, it worsened it in women.

“Furthermore, women should be careful with approaching IF (and calorie restrictions in general) because going without food for extended periods can slow down non-essential functions like reproduction, digestion, and weight loss.”


If you need support from a PCOS nutritionist, we have over 500 registered therapists who can support you. Search today.

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“A study done on IF in 2013 found that females stopped ovulating, too. IF has also been linked to a cascade of hormone imbalances in women such as disruption of oestrogen, cortisol and thyroid hormones.”

Anna concludes that intermittent fasting might not be the best solution for people who already suffer from the following:

  • ongoing hormonal imbalances
  • infertility
  • blood sugar issues 
  • those who suffer from insulin-resistant PCOS

Can women with PCOS approach intermittent fasting safely?

Anna says that gentle intermittent fasting is a safer option and recommends the following:

  • Use your sleep time as your ‘IF window’.
  • Have your last meal two hours before your bedtime, then try to sleep for eight hours.
  • Eat your breakfast no longer than 30 minutes after waking up. This is specifically important for those with an insulin-resistant type of PCOS. 

“Applying the above should, in theory, give you a 10 hour IF window (with eight of those occurring during sleep).”

Additionally, she suggests:

  • Don’t fast when you’re bleeding.
  • During your eating window, choose the best diet for your hormonal health (as per the advice given by your nutrition professional).

Anna Löfgren specialises in female hormonal health conditions. If you’d like more information about Anna’s practice, read her Therapist spotlight interview, browse her profile or send her a direct message.


When IF does work for people with PCOS

So whilst fasting may or may not work for some in the treatment of PCOS, there certainly isn’t one size that fits all. Tarryn Poulton, nutrition coach and founder of PCOS Diet Support, has PCOS and follows a PCOS diet as a form of treatment. 

Having tried intermittent fasting herself, Tarryn has seen numerous success stories with women in her clinic in terms of reducing insulin and blood glucose levels, thereby improving ovarian function, androgen excess and fertility.

Three women smiling

“In working with clients and practising intermittent fasting myself, I have seen women with PCOS lose weight, regain their menstrual cycle and see improvements in many of their PCOS symptoms.

“Whilst this all sounds great, there are some things that women with PCOS need to be aware of:

  • If you are intermittent fasting, it is important to watch that you don’t overeat during your feasting window.
  • Women with PCOS are prone to disordered eating and this can be exacerbated with intermittent fasting.
  • Women who are pregnant should not practise intermittent fasting.”

Is intermittent fasting right for you?

So, on the one hand, there are many strong advocates for this method, particularly in relation to weight gain and PCOS. Last year, Instagrammer Jen Wagener told Women’s Health she conquered her PCOS-weight gain through intermittent fasting, a practice she has continued to help maintain a healthy weight. This you could say, was a success for IF and PCOS.

But with very little scientific evidence to support this theory, if you do decide that IF is for you, it’s important to work with a nutrition professional or your GP and start introducing the process gradually. Elongated periods of fasting could lead to overconsumption in the feast periods, if you have a difficult relationship with food or a history of eating disorders, this practice could trigger unhealthy habits and attitudes.

If you struggle with symptoms of PCOS, you can reach out to a nutrition professional in your local area, or find one offering online services. If you have had experience with intermittent fasting and PCOS and would like to share your story, we’d love to hear from you.

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Written by Katie Hoare

Katie is Digital Marketing and Content Officer at Nutritionist Resource.

Written by Katie Hoare

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