PCOS and Blood Sugar: Why a Low Glycemic Index Diet Can Improve Hormones and Energy

Written by Sam Thompson, Registered Dietitian (RD)

If you have PCOS, chances are you’ve heard some version of this advice: cut carbs, lose weight, eat healthier.

But what you probably weren’t told is why or how any of that actually connects to your hormones.

For most people with PCOS insulin resistance is a key piece of the puzzle. And when insulin isn’t working well, symptoms like irregular cycles, acne, fatigue, and fertility challenges often follow.

One of the most evidence-supported nutrition approaches for improving insulin sensitivity, hormone balance, and even fertility in PCOS is the low glycemic index (GI) diet. Not keto. Not carb-free. Not another restrictive plan that leaves you burnt out.

Let’s break down what a low GI approach really is, why it’s so relevant for PCOS, and how to think about applying it in real life.

Why Blood Sugar Matters in PCOS

Insulin resistance is considered a key driver of PCOS. Research shows that up to 75% of lean women and 95% of women with higher body weight with PCOS demonstrate some degree of insulin resistance.

When insulin levels run high, it can:

• Stimulate excess androgen (testosterone) production

• Disrupt ovulation and menstrual regularity

• Increase inflammation

• Promote abdominal fat storage

• Worsen acne and hair growth

This is why improving how your body responds to carbohydrates is often more important than simply reducing carbs.

What is the Glycemic Index

The glycemic index (GI) ranks carbohydrate-containing foods based on how quickly they raise blood glucose levels after eating.

Low GI foods (<55) digest more slowly and lead to steadier blood sugar and insulin levels

High GI foods (>70) are rapidly digested, causing sharp blood sugar spikes followed by crashes

Low GI foods also tend to be:

• Higher in fiber

• More nutrient-dense

• More filling and satisfying

What the Research Says About Low GI Diets for PCOS

A 2021 systematic review and meta-analysis examining low glycemic index diets in women with PCOS found consistent benefits compared to control diets, including:

• Improved insulin sensitivity (lower fasting insulin and HOMA-IR)

• Improved lipid profiles (lower total cholesterol, LDL, and triglycerides)

• Improvements in reproductive hormones, including testosterone and SHBG

• Reduced waist circumference and body fat

• Improved emotional wellbeing and reduced hirsutism

In other words: the blood sugar insulin relationship effects the whole body.

Low Glycemic Index Doesn't Mean Low-Carb

One of the biggest misconceptions I see in PCOS is the belief that carbs are the problem and in order to manage PCOS one needs to be on a low carb or no carb diet.

When in reality, the type, timing, portion size and context of carbohydrates are what matter most.

A large meta-analyses showed that dietary patterns emphasizing:

• Whole grains

• Legumes

• Vegetables

• Fruits

• Healthy fats

can improve insulin resistance just as effectively or more effectively than low-carbohydrate diets, with better long-term adherence and fewer side effects

The Common Thread: Fiber

The Low Glycemic Index Diet isn't the only diet shown to improve PCOS symptoms, but one thing they all tend to share is fiber.

Low GI diets tend to be high in fiber, which:

• Slows glucose absorption

• Improves insulin sensitivity

• Supports gut health and estrogen metabolism

• Increases satiety and reduces cravings

Most adults consume 10–15 g of fiber per day, while research-supported targets for metabolic health fall closer to 25–35 g per day. This gap alone can explain why many people with PCOS constantly feel hungry, fatigued, or stuck in a blood sugar rollercoaster, even when eating “healthy.”

What Low GI Eating Looks Like in Real Life

It often includes:

• Whole grains instead of refined grains

• Beans, lentils, and vegetables as carb sources

• Pairing carbohydrates with protein, fat, and fiber

• Following a regular meal pattern; eating every 3-4 hours

  
  

A full list of low, moderate, and high glycemic foods can be found on Diabetes Canada's website.

Personalized Support

If you have PCOS and are interested in building a personalized strategy that works for your body, your symptoms, and your life consider working with a Registered Dietitian.

At Sam Thompson Nutrition, I work with women with PCOS to:

• Improve insulin sensitivity and hormone balance

• Create sustainable meal strategies (without rigid rules)

• Support fertility, cycle regularity, and metabolic health

• Feel confident in their food choices again

Book a free 15 minute discovery call today!

Get Started

Citations:

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Diamanti-Kandarakis, E., & Dunaif, A. (2012). Insulin resistance and the polycystic ovary syndrome revisited: An update on mechanisms and implications. Endocrine Reviews, 33(6), 981–1030. https://doi.org/10.1210/er.2011-1034

Goodman, N. F., Cobin, R. H., Futterweit, W., Glueck, J. S., Legro, R. S., & Carmina, E. (2015). American Association of Clinical Endocrinologists, American College of Endocrinology, and Androgen Excess and PCOS Society disease state clinical review: Guide to the best practices in the evaluation and treatment of polycystic ovary syndrome. Endocrine Practice, 21(11), 1291–1300. https://doi.org/10.4158/EP15748.DSC

Legro, R. S., Castracane, V. D., & Kauffman, R. P. (2004). Detecting insulin resistance in polycystic ovary syndrome: Purposes and pitfalls. Obstetrical & Gynecological Survey, 59(2), 141–154. https://doi.org/10.1097/01.OGX.0000109523.25076.E2

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Azziz, R., Carmina, E., Chen, Z., Dunaif, A., Laven, J. S. E., Legro, R. S., & Yildiz, B. O. (2016). Polycystic ovary syndrome. Nature Reviews Disease Primers, 2, 16057. https://doi.org/10.1038/nrdp.2016.57

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