PMOS Myth-busting: What Does the Science Really Say?

PMOS, previously known as PCOS, is one of the most common endocrine conditions affecting women, yet it remains surrounded by misinformation. Search online and you may be told that you need to lose weight, stop eating carbs, exclude dairy and gluten, take a pricey supplement, or identify your exact “type” of PMOS before you can improve your health.

Some of these ideas contain a grain of science. Others are misleading. And some can make an already complicated condition even harder to navigate.

So, for PMOS Awareness Month, let's look at what the evidence actually tells us.

Myth 1: You need ovarian cysts to have PMOS
Despite the old name, you do not need ovarian cysts to have PMOS. In fact, what have traditionally been described as “cysts” are actually numerous small ovarian follicles rather than cysts in the usual medical sense.

In adults, diagnosis generally requires two of three features: ovulatory dysfunction, clinical or biochemical androgen excess, and polycystic ovarian morphology on ultrasound or elevated AMH where appropriate. This means someone can have irregular periods and androgen excess and meet the diagnostic criteria without having polycystic ovaries at all.

Equally, an ultrasound showing polycystic ovarian morphology does not automatically mean someone has PMOS. 

Myth 2: PMOS only affects women who are overweight
PMOS can occur at any body size. Higher body weight can worsen insulin resistance and some metabolic features in susceptible individuals, but it does not cause PMOS.

Insulin resistance can also occur in women with a BMI within the healthy range. The Monash International Evidence-Based Guideline specifically states that women with PMOS have an increased risk of impaired glucose tolerance and type 2 diabetes regardless of age or BMI.

Myth 3: You need to cut out carbohydrates
Carbs have acquired a particularly bad reputation in the PMOS world because of the relationship between glucose, insulin and insulin resistance.

But having insulin resistance does not mean carbohydrates need to disappear from your diet altogether.

The international guideline concludes that there is no evidence that one particular macronutrient composition is superior for everybody with PMOS. What we eat alongside carbohydrates, the amount we eat, how processed they are, and our overall dietary pattern all influence the glucose response.

There is a considerable nutritional difference between a sugary drink and a meal containing lentils, vegetables and wholegrains, yet all contain carbohydrate.

Myth 4: Everyone with PMOS should give up gluten and dairy
There is currently no recommendation in the international PMOS guideline for routine gluten or dairy exclusion.

Someone with coeliac disease needs to avoid gluten. Someone with lactose intolerance may benefit from adapting their dairy intake. Food allergy or other gastrointestinal conditions may require individual dietary changes.

But that is completely different from saying gluten or dairy causes PMOS.

Unnecessary exclusion can also reduce dietary variety and make it harder to obtain nutrients such as fibre, calcium, iodine and protein, depending on what foods are removed and how they are replaced.

Your diet should be personalised because of your health needs, not because everybody with PMOS has been given the same prohibited-food list.

Myth 5: Losing weight will cure PMOS
Weight loss may improve metabolic and reproductive outcomes for some women living with excess weight, but weight loss is not a cure for PMOS.

PMOS also occurs in lean women, and the underlying genetic and endocrine susceptibility does not disappear because somebody reaches a particular number on the scales.

Importantly, the international guideline recognises that healthy lifestyle changes have benefits even in the absence of weight loss.

Physical activity can improve insulin sensitivity. Resistance training can support muscle and glucose disposal. A nutritious diet can improve diet quality and cardiometabolic health. Better sleep and stress management may influence metabolic and psychological wellbeing.

Those changes have value even when somebody's weight remains stable.

The guideline also specifically calls upon healthcare professionals to recognise and minimise weight stigma in PMOS care.

Myth 6: There are four root-cause types of PMOS
You may have seen quizzes telling you that you have “insulin-resistant PCOS”, “adrenal PCOS”, “inflammatory PCOS” or “post-pill PCOS”.

This is not an internationally recognised diagnostic classification.

There are recognised PMOS phenotypes based on different combinations of ovulatory dysfunction, hyperandrogenism and polycystic ovarian morphology.

And there is absolutely biological variation within PMOS. Insulin resistance may be particularly prominent in one person. Another may have significant adrenal androgen production. Inflammation, stress physiology, sleep and metabolic health can vary considerably between individuals.

But these systems also interact. They do not divide neatly into separate boxes.

For example, somebody may have insulin resistance, raised adrenal androgens, and increased inflammatory signalling simultaneously.

Understanding individual drivers can be useful. Believing that everyone belongs to one simple “root cause type” is less helpful.

Myth 7: A supplement can “balance your hormones”
If only it were that simple.

Supplements including inositol, vitamin D, omega-3 fatty acids, NAC and various herbal products are widely promoted for PMOS.

Some have interesting evidence, but the quality and consistency of that evidence vary considerably.

Supplements can form part of an individualised programme, but they should not replace assessment of nutrition, sleep, physical activity, metabolic health or appropriate medical care.

Myth 8: PMOS only matters if you want to get pregnant
This may be the most damaging misconception of all.

PMOS is a leading cause of ovulatory infertility, but fertility is only one part of the condition.

Women with PMOS have increased risks relating to impaired glucose tolerance and type 2 diabetes, cardiovascular risk factors, obstructive sleep apnoea and endometrial health. Anxiety, depression, body-image distress and disordered eating are also considerably more common.

This is why modern PMOS care should consider metabolic, cardiovascular, psychological and sleep health as well as periods and fertility.

Nobody should be told to simply “come back when you want a baby”.

Myth 9: If you have PMOS, you won't be able to get pregnant
PMOS can make conception more difficult, particularly when ovulation is irregular or absent.

But PMOS does not mean infertility is inevitable.

Some women with PMOS ovulate regularly, while others ovulate intermittently. Many conceive naturally, and effective fertility treatments are available when help is needed.

If pregnancy is a goal, improving preconception health is worthwhile, but women should also know that they have evidence-based treatment options rather than feeling that PMOS has removed the possibility of motherhood.

Myth 10: Perhaps the biggest myth: there is one answer for everyone
If there is one message to take away from PMOS Awareness Month, it is that PMOS affects every woman differently. 

That means good PMOS care should not begin with: “Everyone with PCOS needs to do this.”

It should begin with: “What is happening for you?”

But there is a growing evidence base that can help us understand the condition, identify individual priorities and make informed decisions about long-term health. And that is far more useful than another list of foods you're apparently never allowed to eat again.