PCOS and Nutrition: Evidence-Based Strategies Beyond 'Just Lose Weight'

If you have polycystic ovary syndrome (PCOS), you have probably been handed some version of the same advice: just lose weight. As a dietitian, I find this both unhelpful and, frankly, a little dismissive. It collapses a complex hormonal and metabolic condition into a single number on a set of scales. The evidence tells a more nuanced and, I think, more hopeful story.

What PCOS is — and the insulin connection

PCOS is the most common hormonal condition in women of reproductive age, affecting somewhere between 8 and 13 per cent of women depending on how it is defined.^[1] It is diagnosed when at least two of three features are present: irregular or absent ovulation, signs of excess androgens (such as acne or unwanted hair growth), and the characteristic appearance of the ovaries on ultrasound.^[1]

A central thread running through PCOS is insulin resistance. Many women with PCOS — including those in a lean body — have cells that respond poorly to insulin, so the body compensates by producing more of it. Those higher insulin levels in turn drive the ovaries to make more androgens, which is part of why symptoms like irregular cycles and acne appear. This is why the international evidence-based guideline frames PCOS as a metabolic condition, not merely a cosmetic or fertility one.^[1]

Why "just lose weight" misses the point

Weight is part of the conversation for some women, but it is far from the whole story. Plenty of women with PCOS are not in a larger body at all, yet still experience insulin resistance and irregular cycles. The international guideline recommends lifestyle change as first-line management for everyone with PCOS, with weight loss as a goal only where appropriate, and it explicitly cautions against weight stigma.^[1] A 2019 Cochrane review of lifestyle interventions found they may improve the free androgen index, body weight and BMI, although the certainty of evidence was low.^[2]

Diet quality and the low-GI approach

If insulin is part of the problem, then it makes sense to eat in a way that asks less of it. One of the better randomised trials compared a low-glycaemic-index diet with a conventional healthy diet in overweight women with PCOS. Even when weight loss was similar between the two groups, the low-GI group showed greater improvement in insulin sensitivity, and notably more of them regained regular menstrual cycles.^[3] This does not mean carbohydrates are the enemy — it points to favouring slower-digesting, higher-fibre carbohydrates over highly refined ones. The best dietary pattern is one you can actually live with.

Movement matters in its own right

A 2019 systematic review and meta-analysis found that exercise — whether or not it was combined with diet — significantly improved insulin resistance and body composition, with the largest benefits in women in larger bodies, and crucially independent of dramatic weight change.^[4] The guideline's activity recommendations are reassuringly ordinary: at least 150 minutes of moderate activity per week, ideally with some muscle-strengthening work.^[1]

What about myo-inositol?

Myo-inositol is the supplement I am asked about most. It is involved in insulin signalling, and there is genuine interest in it. But a 2018 Cochrane review of inositol in subfertile women with PCOS concluded that we are uncertain whether it improves live birth or clinical pregnancy rates, because the available trials were small and of very low quality.^[5] It should be considered a possible adjunct rather than a substitute for the lifestyle foundations that do have stronger support.

Managing PCOS sustainably

The thread that ties all of this together is sustainability. PCOS is a long-term condition, and crash diets tend to fail precisely because they cannot be maintained. What works is the unglamorous combination: a higher-quality diet built around minimally processed carbohydrates, regular movement you genuinely enjoy, adequate sleep, and attention to the psychological load that PCOS so often carries.

This article is general information, not personalised medical advice. PCOS should be managed alongside your own healthcare team.

References

1. Teede HJ, Misso ML, Costello MF, et al. Recommendations from the international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Human Reproduction. 2018;33(9):1602–1618. PubMed
2. Lim SS, Hutchison SK, Van Ryswyk E, Norman RJ, Teede HJ, Moran LJ. Lifestyle changes in women with polycystic ovary syndrome. Cochrane Database Syst Rev. 2019;(3):CD007506. PubMed
3. Marsh KA, Steinbeck KS, Atkinson FS, Petocz P, Brand-Miller JC. Effect of a low glycemic index compared with a conventional healthy diet on polycystic ovary syndrome. Am J Clin Nutr. 2010;92(1):83–92. PubMed
4. Kite C, Lahart IM, Afzal I, et al. Exercise, or exercise and diet for the management of polycystic ovary syndrome: a systematic review and meta-analysis. Syst Rev. 2019;8(1):51. PubMed
5. Showell MG, Mackenzie-Proctor R, Jordan V, Hodgson R, Farquhar C. Inositol for subfertile women with polycystic ovary syndrome. Cochrane Database Syst Rev. 2018;(12):CD012378. PubMed