Lean PCOS: What Causes It and How To Treat It

Searching for information online about PCOS can be confusing and overwhelming. It may seem even more difficult if you are a lean woman with PCOS because you may not meet the stereotypical criteria of PCOS.

Unfortunately, there is this perception that all women with PCOS are overweight or obese. This stereotypical image has meant lean women with PCOS go undiagnosed.

But you can be a normal weight and have PCOS. And lean PCOS is more common than you think.

So, in this post, we will look at what causes lean PCOS and how to treat it.

Let’s begin.

Can you be thin and have PCOS?

PCOS is commonly associated with weight gain and obesity. But because of this stereotypical image, thin or lean PCOS women may go undiagnosed. PCOS is a condition where female sex hormone are imbalanced. In lean women with PCOS, the hormone imbalance can occur because of insulin resistance and high cortisol levels. So by making diet and lifestyle changes, you can begin to rebalance your hormones and reverse your PCOS symptoms.

What is Lean PCOS?

Researchers have found that between 20–50% of women with PCOS are normal weight or thin. So, lean PCOS simply means you have PCOS but you have a body mass index (BMI) less than 25.

Now, while lean women with PCOS do not struggle with weight problems, this does not mean everything is working fine inside. Lean PCOS women still suffer from the same hormonal imbalance. They still produce high levels of testosterone and have metabolic problems like the ‘classic’ PCOS woman.

So, you might be wondering.

What Causes Lean PCOS?

Contrary to popular belief, PCOS is not one condition and there isn’t one type of lean PCOS. Every PCOS woman suffers from a different type of PCOS that develops for a specific reason. Meaning, there is a root cause to the hormonal imbalance and symptoms women with PCOS are experiencing. Now, the root cause tends to be the same regardless if it is lean or ‘classic’ PCOS.

Insulin Resistance

Insulin resistance affects around 30% of lean PCOS women.

So our bodies main source of energy is glucose (sugar) and we get this from the food we eat. The sugar we get from food enters our bloodstream after digestion. Now insulin is a hormone released by the pancreas, that works to take sugar out of the bloodstream and send it to the cells of the body. As you can see in figure 1, in a healthy individual blood sugar levels rise slightly after eating a meal. But then insulin lowers it back to normal. However, when someone is insulin resistant, the cells in the body don’t respond well to insulin and can’t shuttle the sugar out of the blood.

Now, the cause of insulin resistance in both ‘classic’ and lean PCOS women are different. I will first start by talking about ‘classic’ PCOS insulin resistance.

Figure 1- Blood Sugar Response After Eating Simple Carbs


Insulin Resistance in ‘Classic’ PCOS

‘Classic’ PCOS women often experience high blood sugar levels after eating a meal (hyperglycemia). This then triggers the release of insulin to send the sugar to the cells. High amounts of insulin are secreted which causes blood sugar levels to drop very low (a blood sugar crash). This rise and fall in blood sugar levels is called a 'blood sugar rollercoaster'.

Now, the problem occurs when blood sugar levels are high which causes insulin to be constantly secreted. You see, the constant release of insulin eventually causes the body to become desensitized. As a result, the cells become resistant to the effects of insulin.

But the pancreas continues to release more and more insulin to lower blood sugar levels. The high levels of insulin in the body then has the unwanted side effect of telling the ovaries to produce more androgens. Which then causes the PCOS symptoms women experience.

In contrast to this, the cause of insulin resistance in lean PCOS women is different.

Let me explain.

Lean PCOS Insulin Resistance

So here’s the thing.

Researchers state that many lean PCOS women suffer from reactive hypoglycaemia. This is where fasting blood sugar levels are normal before eating, but roughly 1 and half to 5 hours after eating, blood sugar levels drop very low. This can be seen in figure 1.

Now, you might be wondering why this happens. So, I have created a visual graphic, figure 2, to help explain.

Figure 2- How Insulin Resistance Develops in Lean PCOS Women

Dr. Fiona McCulloch, a naturopathic doctor, reveals that lean women with PCOS suffer from insulin hypersensitivity. Meaning the body will overproduce insulin to compensate for its low sensitivity to insulin. Now, the overproduction of insulin leads to a severe drop in blood sugar levels. This then causes the individual to feel hungry, dizzy and fatigued. Resulting in them eating more sugar to raise blood sugar levels but the excess energy is stored in fat cells.

Over time, the cells in the body become resistant or desensitized to the high levels of insulin. This is when insulin resistance develops.

Now, you might be wondering.

How can you be lean and suffer from insulin resistance?

So here’s the thing.

A low body weight doesn’t mean a low body fat percentage.


You can be a low body weight but have a high body fat percentage. Meaning you may be carrying too much visceral fat. This is a type of fat that is stored in your abdominal area, which puts you at a greater risk of insulin resistance.

One simple way to find out if you have too much visceral fat is to assess your waist-to-hip ratio. A large waist-to-hip ratio can be a marker of insulin resistance and a higher risk for Type 2 Diabetes.

Chronic Stress

High cortisol is another common root cause of lean PCOS.

When we are stressed we go into fight or flight mode. Our body evolved to keep us safe in the wild. It cannot distinguish between you needing to run away from a tiger and you feeling stressed due to a work meeting. The body responds in the same way, with the adrenals releasing cortisol into the bloodstream.

In addition to the release of cortisol, the adrenals produce androgens including DHEA, DHEA-S, and androstenedione. These male hormones try to protect the body from the damaging effects of too much cortisol. However, the longer cortisol stays high, the more androgens are released. This then causes a hormonal imbalance and the development of PCOS.

A study showed DHEA-S levels were higher in lean PCOS women than their counterparts and non-PCOS women.

Stress can include both psychological and non-psychological.

For example:

  • Over-Exercising and High-Intensity Exercise
  • Low-Calorie Dieting
  • Inflammation
  • Lack of Sleep
  • Over Consuming Caffeine
  • Autoimmune Disease
  • Environmental Toxins

Diagnosing lean PCOS

To find out if you have lean PCOS, you must visit your doctor to do the necessary tests. The tests your doctor may run include an oral glucose tolerance test or a mixed meal tolerance test. These tests measure a patient’s blood sugar levels and can show how much insulin the pancreas releases in response to the sugar consumed.

Oral Glucose Tolerance Test with Insulin

Experts say this is the best way to test for insulin resistance because it measures both glucose and insulin.

The oral glucose tolerance test with insulin involves an overnight fast. So, no eating or drinking at least eight-twelve hours before the test. On the day of the test, patients will drink eight ounces of fluid containing 75 grams of sugar before bloodwork is run.

At certain intervals during the 2-4 hour duration of the test, glucose is measured along with insulin.

Mixed Meal Tolerance Test (MMTT)

The mixed meal tolerance test involves the patient drinking a liquid meal that contains protein, fats and carbohydrates. The doctor will draw blood samples every thirty minutes for two hours.

Doctors want to see how much insulin your pancreas produces after drinking the meal. So, what they are looking to see is, insulin levels to change and a drop in blood sugar levels, below fasting level, within a few hours.

High DHEA-S Levels

Higher DHEA-S levels are more common in lean women with PCOS. So, doctors will test this to see your PCOS is a result of adrenal androgen excess.

Now, the result is relative to age. So if the DHEA-S value is high for your age, it’s a sign your producing too many male hormones from your adrenals.

Higher LH to FSH compared to classic PCOS

Luteinizing Hormone is released by the anterior pituitary gland (a region in the brain) that controls the function of the female ovaries. This hormone works closely with follicle-stimulating hormone (FSH), another hormone made in the pituitary gland. FSH stimulates the growth of ovarian follicles and the production of estrogen. As these follicles grow, estrogen levels increase. The increase in estrogen causes luteinizing hormone to rise rapidly. This then triggers ovulation (roughly week two of the menstrual cycle).

Researchers have found that lean PCOS women have a higher LH to FSH ratio compared to overweight and obese women with PCOS. Doctors will assess your ratio of LH to FSH to get an indication it you are suffering from lean PCOS.

To find out what causes high levels of LH check out my post.

Higher Beta Endorphins

Beta endorphins are proteins that are mostly created by the pituitary gland in response to stressors, like pain. The role of endorphins is to reduce our perception of pain. A study found lean PCOS women have higher beta endorphins than lean non-PCOS women.

The problem with too many endorphins is that the fight-or-flight response is always triggered.  If the body is flooded with endorphins, it assumes a painful experience is coming.

The more your body goes into the fight or flight response, the more it is unable to switch off. Resulting in the stress response constantly being activated and cortisol levels remaining high.

You might be wondering.

How Do I Treat Lean PCOS?

So, here’s the thing.

The right treatment approach for you will be dependent on the root cause of your PCOS and hormone imbalance. Treatment will vary based on whether your PCOS is caused by high insulin levels or chronic stress.

Balance Blood Sugar Levels and Lower Insulin Levels

To balance your hormones and reverse your PCOS symptoms, balancing your blood sugar levels is key. Here’s what you can do to achieve this.

Combine carbohydrates with protein and fat

Avoid eating a high carb meal. Instead prepare balanced meals that contain all three macronutrients, protein, carbs and fat.

By combining carbs with protein and fat, spikes in insulin are reduced.

Eat high fiber foods

Studies show fiber can lower blood sugar levels by slowing down digestion and the release of sugar.

Eat more Frequently

Going too many hours without eating causes your blood sugar levels to drop. This is because sugar levels have not been replenished. Eat small meals and snacks no more than 3 hours apart. This can help prevent low blood sugar levels.

Resistance Training

Resistance training is any type of exercise that causes the muscles to contract. Resulting in increased strength, muscle mass and endurance.

A study found each 10% increase in muscle was associated with an 11% relative reduction in insulin resistance. So, the more muscle you have, the better insulin works in the body.

Lower stress

Stress management is yet another key component to managing blood sugar levels. This is because cortisol raises blood sugar levels which then leads to an increase in insulin.

Vitamin D

Vitamin D is needed for the absorption of calcium, magnesium and phosphate. It is also needed for strong bones and muscles. A study found low vitamin D levels may cause insulin resistance in women with PCOS. So, by getting more sunlight and eating vitamin D rich foods like mushrooms, beef liver and eggs, insulin resistance can decrease.


Inositol is a substance, often referred to as Vitamin B8, that is naturally occurring in most foods. Though it is highest in whole grains and citrus fruits. Research shows it can act like insulin in the body and help it work better.

(to find out more about inositol, read this post).

But before you add any of these supplements to your diet, consult a medical professional.

Lower Cortisol Levels

Managing your stress is key to hormonal balance. But especially important if your lean PCOS is a result of adrenal androgen excess. So, make it a priority to find ways to lower your stress levels. Take a look at all psychological and non-psychological stressors in your life. See where you need to make some changes to remove or lower them. This may mean

Stopping high-intensity workouts

High intensity and endurance workouts increase cortisol levels. So, instead, opt for low-intensity exercises like walking, swimming and yoga. Low-intensity exercises do not significantly increase cortisol.

Avoiding caffeine

Here’s the thing.

Caffeine is a stimulant because it activates the stress response and causes the adrenal glands to release cortisol. So, to lower cortisol levels you may have to avoid or cut back on your caffeine consumption.

For more information on caffeine for PCOS and which coffee I drink to manage the release of cortisol. Check out my ‘Caffeine and PCOS: Should You Avoid It?’ post.


Many people, unfortunately, do not prioritize sleep. As a result, they do not have a bedtime routine to ensure good quality sleep. Research shows sleep deprivation can increase cortisol levels.

So, aim to go to bed between 9-11 pm and strive for 7-8 hours of sleep. To help you do this, avoid all blue light, so no looking at your mobile phone or any screen at least 1 hour before bed. Going for a walk and eating foods that contain tryptophan (a sleep-inducing amino acid) like turkey, spinach and nuts, can help your body relax.

Is it Lean PCOS?

In summary, you can be a normal weight or lean and have PCOS.

While these women do not struggle with their weight, they still have the same hormonal imbalance.

Lean PCOS has various root causes including insulin resistance and high cortisol.

The only way to know for sure if you have lean PCOS is to do the tests. Doctors may run an insulin glucose tolerance test and they may also look at your DHEA-S level. Doctors could also look at your LH:FSH ratio and beta endorphins.

Address the Root Cause

Depending on what is causing your lean PCOS, there are certain dietary and lifestyle changes you can make.

If lean PCOS is a result of insulin resistance, working on balancing blood sugar levels is key. This can be achieved by combining your carbs with protein and fat, eating more fiber and every 3-4 hours. As well as doing resistance training, lowering stress and supplementing with vitamin D and inositol.

Lean PCOS caused by high cortisol requires a focus on lowering stress levels. To achieve this you may have to avoid high-intensity workouts, focus on getting better sleep and cutting back on the caffeine. Add long walks in nature, yoga or meditation into your daily routine.

Restoring hormonal balance takes time, so it is important you remain patient.


Hey there! I am Despina Pavlou, founder of PCOS Oracle and online coach. I want to share with you the diet and lifestyle changes I made to naturally reverse my PCOS and achieve hormonal balance. I believe using my holistic approach you too can take back control from PCOS.

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