Is the Keto Diet Good for PCOS?

By Clare Goodwin

Last updated: September 3, 2020

If you look anywhere online then you’ll see women talking about the keto diet for PCOS. But what is the keto (ketogenic) diet and is it even good for PCOS?

I’d recommend you read on to hear who the ketogenic diet is (and isn’t) suitable for, plus some information about the downsides of it.

What Is the Keto Diet and How Does It Work?

The keto diet changes the “fuel” that our body uses for energy. You can think of it like converting a petrol car to an electric car. Like a car with a petrol motor, our bodies have adapted to have a ‘sugar’ motor as sugar is a really easy fuel for us to run off. We get this sugar by breaking down carbohydrates from foods like sweets, chocolate, rice, bread, pasta, etc.

However, severely restricting sugars (carbohydrates) from our diet forces our body to run off the fuel provided by our stored body fat. Using the car analogy, this is like converting a petrol car to an electric one. Ketosis is the processes of converting our ‘sugar motor’ to a ‘fat motor’.

Why Are Carbs So Important In PCOS?

Carbs get a lot of attention in PCOS because of insulin resistance, which 70% of women with PCOS have. If you don’t know whether or not you have it then please read my Introductory Guide To Insulin Resistance (1).

Insulin is our storage hormone. When we eat, our body detects a rise in blood sugar. Our body doesn’t like blood sugar to be high for long periods of time as it can damage multiple body and organ cells. We therefore store the sugar in our muscles and liver for later use.

Insulin is the hormone that tells the cells to open up and let the glucose in, similar to the way a key opens a door. When the key has been used too much, or the lock gets inflamed, the lock starts to get a bit worn and clogged up and the key no longer fits. This is insulin resistance.

Insulin resistance causes blood glucose to stay high. The result of this is that the pancreas produces more insulin to try and reduce blood glucose levels. However, if this continues over a long period of time then the pancreas becomes so fatigued that it’s unable to produce adequate levels of insulin. This is called Type 2 Diabetes.

How Many Carbohydrates Can You Eat On A Keto Diet?

If you want your body to go into ketosis then you need to be eating less than 30g of carbohydrates per day.

To give you an example of the amount of carbohydrates in foods:

  • 100g of chocolate contains approximately 50g of carbohydrates.
  • 1 cup of spaghetti contains 40g of carbohydrates.

Therefore, instead of sugars, bread and pasta, a keto diet means filling your meals with lots of green leafy vegetables, proteins and good fats.

Keto Diet For PCOS: Is It Right For You?

Firstly, it’s important to note that there is not ONE TYPE OF PCOS (2), therefore there is not one best diet. PCOS is a syndrome, which means that while we might all have high androgens, missing periods or ‘cysts’ on the ovaries, we have different underlying root causes for these problems. The main cause that I mentioned above is insulin resistance (3), but PCOS can also be caused by high stress hormones.

50% of women with PCOS have high DHEA-S levels, meaning that their stress hormones are overactive. For these women, a low carb diet would put more stress on their adrenal glands and potentially result in worsening symptoms. But for some women with PCOS – especially those with insulin resistance and obesity – a ketogenic diet can work really well.

Keto Diet For PCOS: How Can It Help?

The Keto Diet can reduce chronic inflammation

One of the ways the keto diet helps to reduce insulin resistance is by reducing inflammation. Ketone bodies are produced when the body is in a state of ketosis. These ketone bodies release a compound that blocks our inflammatory genes (4) – that’s pretty remarkable! This is partly the reason why the keto diet has been so successfully used to treat lots of different conditions, including Alzheimer’s (5).

As inflammation contributes to insulin resistance and PCOS (6), a diet that reduces inflammation is definitely worth considering.

The Keto Diet can help you lose weight

The keto diet can be effective for weight loss because it forces your body to use its fat reserves for energy. A small pilot study on overweight women with PCOS found that a ketogenic helped to reduce body weight by 12% (7). The keto diet also helped to lower testosterone too.

The Keto Diet can reverse insulin resistance

70-80% of women with PCOS have insulin resistance (8). High levels of insulin increase testosterone which cause the facial hair growth, acne, hair loss, and missing periods. Therefore, any diet which helps to improve insulin resistance and stabilise your blood sugar is worth looking into.

One study found that a keto diet helped to reverse Type 2 diabetes in 10 weeks (9). These results were maintained for up to a year with an average weight loss of 30lbs (10).

But remember it’s not the only way to reverse insulin resistance. Studies have shown there are many other dietary strategies (11, 12) that can have a similar outcome.

What Are the Downsides of a Ketogenic Diet?

It starved our gut, which could lead to weight gain

The main reason that I don’t recommend women stay on keto diets for years and years is because it starves our gut bacteria. Our gut is really important for our health. Not only does it make up 70% of our immune system (13), but the bacteria in there also control how many calories and carbs (14) we absorb from our food, helping to keep us lean.

Poor gut bacteria also causes inflammation (15)and insulin resistance (16), which both contribute to PCOS. Gut bacteria and the cells lining our gut (17)can only survive if we feed them resistant starch.

Resistant starch is something that we can’t digest, but it’s great food for our bacteria. This starch is in starchy carbohydrates that have been cooked and cooled, like cold rice (sushi), legumes, leftover cooked potatoes and other root vegetables, green bananas or plantains. Studies show that diets low in resistant starch (i.e. a Keto diet) reduce the amount of good bacteria (18) we have.

It’s worth considering this point, given that studies on PCOS have shown that we already have too much bad bacteria (19) and not enough of the good bacteria.

Long-term low carb diets can make you lose your period

If you have insulin resistance then the keto diet can be great for bringing your period back. However, it can have the opposite effect if maintained for too long.

Researchers found that women actually need carbohydrates to ovulate and get periods (20). Consuming too few carbohydrates disrupts luteinising hormone, which is the hormone that releases the egg so that we ovulate.

For this reason, I only ever recommend using a keto diet to reverse insulin resistance. As soon as that’s achieved, I recommend reintroducing starchy carbohydrates like potatoes, sweet potatoes and other root vegetables.

It’s not the only way to reverse insulin resistance and lose weight with PCOS

While a keto diet can be really beneficial for some women with PCOS, insulin resistance, and particularly obesity, it certainly isn’t suitable or necessary for all women with PCOS. If your insulin resistance is milder then you likely don’t need to go fully ketogenic. Instead, a more moderate carb intake (i.e. 80-100g from starchy root vegetables) might suit you.
In my other articles I’ve explained how removing some of the more insulin spiking foods, like sugar, gluten and dairy (21), and doing daily strength training (22) is incredibly effective. There are also some supplements and herbs that are really beneficial too.

Summary: Keto Diet for PCOS

  • The keto diet can be a very effective tool for weight-loss and improving insulin resistance, therefore reducing testosterone. But it’s not suitable for all women, especially those with high stress hormones or DHEA-S.
  • I find that removing the biggest offenders (like sugar and sweeteners) is this most important first step. Then add in some other well-proven methods, like strength training, supplements to help improve insulin sensitivity and even intermittent fasting. If you’ve implemented these steps, and you have low stress hormones, then trying the keto diet could be a good option for you.
  • If you do try the keto diet then I recommend cycling in and out of it. This might mean that you stay on a keto diet for 3-6 months, then add some starchy carbs back in for 1 month to feed your gut bacteria.
  • Had success with a keto diet but found that it’s stopped working or you’ve now lost your period? It might be time to add some carbohydrates back into your diet again.


(1) Insulin Resistance and PCOS Introduction
(2) What’s Causing Your PCOS?
(3) Prevalence of Insulin Resistance in PCOS
(4) The ketone metabolite β-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease.
(5) Study of the ketogenic agent AC-1202 in mild to moderate Alzheimer’s disease
(6) Is PCOS an inflammatory process?
(7) The effects of a low-carbohydrate, ketogenic diet on the polycystic ovary syndrome
(8) All Women With PCOS Should Be Treated For Insulin Resistance
(9) A Novel Intervention Including Individualized Nutritional Recommendations Reduces Hemoglobin A1c Level, Medication Use, and Weight in Type 2 Diabetes
(10) Effectiveness and Safety of a Novel Care Model for the Management of Type 2 Diabetes at 1 Year
(11) Beneficial Effects of a High-Protein, Low-Glycemic-Load Hypocaloric Diet in Overweight and Obese Women with Polycystic Ovary Syndrome
(12) The effect of resistant dextrin as a prebiotic on metabolic parameters and androgen level in women with polycystic ovarian syndrome
(13) Allergy and the gastrointestinal system
(14) Mouse study adds to evidence linking gut bacteria and obesity
(15) LPS induced inflammatory responses in human peripheral blood mononuclear cells is mediated through NOX4 and Giα dependent PI-3kinase signalling
(16) The gut microbiota as an environmental factor that regulates fat storage
(17) Butyric Acid: an Ancient Controller of Metabolism, Inflammation and Stress Resistance?
(18) The type and quantity of dietary fat and carbohydrate alter faecal microbiome and short-chain fatty acid excretion in a metabolic syndrome ‘at-risk’ population
(19) Starving our Microbial Self: The Deleterious Consequences of a Diet Deficient in Microbiota-Accessible Carbohydrates
(20) Luteinizing Hormone Pulsatility Is Disrupted at a Threshold of Energy Availability in Regularly Menstruating Women
(21) Which Five Foods Should You Not Eat For PCOS?
(22) What’s the Best Exercise for PCOS Weight Loss?