Not all PCOS cases are the same. A significant number of women I see in my office fit a description of something called “Lean PCOS.” In fact between 20-50% of women who fall into the PCOS category are normal weight or considered “thin” (Nestler 1997). These women have what we would consider a “normal” BMI (Body Mass Index), and may have regular cycles, but they don’t always ovulate and are seeking fertility treatments to get pregnant. 

We need to be aware of this type of PCOS, because the usual medical advice for a woman with PCOS is to lose weight. 

So what is going on? 

Women with Lean PCOS have the following characteristics: 

  • BMI between 18-24.9
  • Cycles might be irregular OR regular
  • she may or may not ovulate
  • she may or may not have concerns with male-pattern hair growth (chin, lips, neck, around nipples)
  • she is seeking fertility treatments to conceive
  • she may be dealing with anxiety or depression, or experience a lower resilience to stress. One study found higher rates of these in lean women with PCOS than in their higher BMI PCOS counterparts.  (Komarowska 2013)
  • she will likely have an elevated LH:FSH ratio on Day 3 bloodwork, meaning greater than 1:1. 
  • she has higher oxidative stress (Yilmaz 2005) 
  • she usually has a normal HbA1C, which really doesn’t tell us enough information. We need more sensitive bloodwork. We want to see fasting insulin and fasting glucose. With those we can calculate something called the HOMA-IR, which we want to see under 2.0. Anything at or above 2 means blood sugar dysregulation. 
  • she might get HANGRY if she goes a length of time without eating.

So they STILL have blood sugar disregulation, even if they are maintaining a normal weight, and we need to address it. 


It’s a deeper issue than hanger. Elevated insulin and glucose have a hormonal effect at the level of the ovaries. They induce androgens to be made, sending a feedback loop to other hormones, like estrogen and LH, meaning they are out of coordination and not working on ovulation as they should be. 

As a result, we may see: 

  • high estrogen on day 3
  • lots of little follicles (also known as an Antral Follicle Count) on Day 3 transvaginal ultrasound. It may sound promising to have lots of follicles, but unfortunately the disregulated hormones prevent them from *maturing* properly. If an egg doesn’t mature it won’t get to ovulation. 
  • because of the above – no ovulation
  • OR delayed ovulation – it takes a long time to get the follicles to mature. 

The good news is that if we can normalize the insulin response, we can change the problematic hormones affecting the ovaries. We can calm down insulin, we normalize LH, total testosterone, free testosterone, and androstenedione, and progesterone. We can calm down oxidative stress that might damage egg quality, and normalize serum lipid profiles. 

So what do we do?

  • Build lean muscle – this means doing resistance training ie lifting weights or doing body weight exercises. Running won’t cut it here. 
  • Get your fasting insulin and fasting glucose levels tested – this is what’s going to tell us where your insulin resistance is at. 
  • Maintain your healthy weight. Work with your healthcare provider if putting on some weight could be beneficial, if your BMI is under 18.5. 
  • Blood sugar balance. You MUST be eating regular protein. I ask patients to have 20-30 g with each meal, and at least 10 g with each snack. Other than meat and eggs, our best friends are protein powder and protein bars – I’m looking at you, my eat-on-the-go patients. 
  • Reach out for emotional support. (Lean women with PCOS are more likely to experience problems with depression and anxiety. Reach out for support, both from friends and professionals.)  Ask us for our favourite fertility related counsellors in your area! 
  • Optimize Vitamin D – shown to help with insulin sensitivity, egg quality, mood. We want it higher than the bare minimum lab cut off. 
  • Acupuncture – normalizes the Hypothalamic-Pituitary-Ovary hormone axis. Typically we would expect to have appointments 1-2 a week to regulate cycles, and while trying to conceive.
  • Inositol – decreases LH if high, lowers hs-CRP (inflammatory marker), androgens, and insulin tolerance test.
  • There are other herbs and supplements that may be useful to further support your hormones, depending on your particular hormone profile. 

For every woman out there with PCOS, I want to be super clear about one thing: you don’t have PCOS because of what or how you ate. You have PCOS because that’s the way you’re built  (Nestler 1997). Science is understanding more and more that there is a genetic predisposition to how certain bodies handle glucose –  whether they are lean or not – and that leads to a diagnosis of PCOS. Even if your food wasn’t the cause, we’re now going to make it part of the remedy –  we’re making our food work harder for us, to nourish us properly.

To learn more about how you can support your fertility, or to book an appointment with Dr. Krause ND, contact us today.

Dr. Camille Krause, Naturopathic Doctor, works collaboratively with your fertility physician to provide safe, complementary, and effective care. By using evidence-based treatments that improve the health of the intended parents, we increase positive clinical outcomes in fertility. After all, healthy eggs and sperm provide the best chances at having healthy babies. In addition to the workup done by your Reproductive Endocrinologist, Dr Krause uses additional specialized testing to select nutrients, botanical medicine, lifestyle, and acupuncture to complement your fertility treatment. Visit her at the Conceive Health Kitchener-Waterloo clinic!

Works Cited: 

Nestler JE, Jakubowicz DJ. Lean Women with Polycystic Ovary Syndrome Respond to Insulin Reduction with Decreases in Ovarian P450c17α Activity and Serum Androgens. The Journal of Clinical Endocrinology & Metabolism, Volume 82, Issue 12, 1 December 1997, Pages 4075–4079. 

Komarowska H, Stangierski A, Warmuz-Stangierska I, Lodyga M, Ochmanska K, Wasko R, Wanic-Kossowska M, Ruchala M. Differences in the psychological and hormonal presentation of lean and obese patients with polycystic ovary syndrome. Neuro Endocrinol Lett. 2013;34(7):669-74

Yilmaz M, Bukan N, Ayvaz G, Karakoç A, Törüner F, Cakir N, Arslan M. The effects of rosiglitazone and metformin on oxidative stress and homocysteine levels in lean patients with polycystic ovary syndrome. Hum Reprod. 2005 Dec;20(12):3333-40. Epub 2005 Aug 25.

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