What Is Polycystic Ovarian Syndrome (PCOS)?

Polycystic ovarian syndrome (PCOS) is the most common endocrine disorder in women of reproductive age, affecting approximately 10-15% of women globally.^1–3 It is often characterized by ovarian cysts, irregular ovulation, irregular menstruation, hyperandrogenism (ie, excess of testosterone), reversal of the ratio of female sex hormones called follicle-stimulating hormone (FSH) and luteinizing hormone (LH), obesity, and insulin resistance. PCOS is also associated with various medical complications including infertility, type 2 diabetes mellitus (T2DM), hypertension, and fatty liver disease.³

What Is the Ketogenic Diet?

The ketogenic diet has gained interest as a potential dietary method to encourage weight loss, improve sex hormone and lipid levels, and normalize ovulation-menstruation cycle in women with PCOS.¹ The diet focuses on a very low consumption of carbohydrates and a very high consumption of fats and has been shown to effectively promote weight loss and improve metabolic profiles in various populations.^4,5

Does the Ketogenic Diet Help With PCOS?

More studies are needed to understand whether ketogenic diet should be encouraged in women with PCOS, but current evidence suggests that the diet may be beneficial.^1,2,6,7 In light of recent research findings, the 2016 position statement by the Italian Society of Endocrinology weakly supported the use of very low-calorie ketogenic diet for overweight or obese women with PCOS who are not responsive to multicomponent standardized diet.^6,7

Studies have found that the ketogenic diet can improve weight, lipid levels, and reproductive hormonal imbalances in women with PCOS.^1,2 For instance, a systematic review and meta-analysis of seven clinical trial (n=170) evaluating the effects of the ketogenic diet in women with PCOS found that >45 days of ketogenic diet intervention resulted in improvements in reproductive hormones and weight.¹ Although the sample size was limited, the review found that the ketogenic diet improved LH/FSH ratio and testosterone levels and significantly reduced weight. A smaller study with 14 overweight women with PCOS investigated the effects of a 12-week ketogenic Mediterranean diet and found similar results.² Significant reductions in body weight, body mass index, fat body mass, visceral adipose tissue, triglyceride levels, total cholesterol levels, and low-density lipoprotein cholesterol levels were observed. The study also noted improvements in insulin resistance measured by the homeostatic model assessment for insulin resistance as well as increases in high-density lipoprotein cholesterol and levels of protein that binds to testosterone (ie, sex hormone binding globulin, SHBG). Reductions in LH/FSH ratio and free testosterone were also found. 

How Does the Ketogenic Diet Help PCOS?

The medical community calls for more rigorous research to uncover the long-term effects of the ketogenic diet on the health of women with PCOS and to elucidate the underlying mechanisms behind the potential benefits of the diet. However, researchers currently hypothesize that the ketogenic diet’s effect on improving weight, insulin sensitivity, and inflammation may be key to understanding how the diet may improve PCOS parameters.¹ 

Pathophysiology of ovulatory dysfunctions and hyperandrogenism in PCOS is intimately linked to insulin resistance.⁷ Studies have also shown that insulin resistance disproportionately affects obese women with PCOS than those who are normal weight. In addition, low-grade inflammation is a common characteristic of PCOS, also known to exacerbate hormonal imbalance and insulin resistance. Research strongly suggests that dietary interventions promoting >5% weight loss can significantly improve various parameters of PCOS. Although there is no prescription that the ketogenic diet is particularly superior to other forms of diet in promoting and sustaining weight loss, evidence suggests that low-carbohydrate diets may be more effective in improving insulin resistance and inflammation than other diets, especially in obese/overweight women with PCOS. Experts have thus proposed that carbohydrate restriction can promote weight loss and improve insulin resistance, hyperinsulinemia, and inflammation, which can subsequently allow normalization of endocrine functions, improvements in LH/FSH ratio, and reductions in testosterone levels in women with PCOS.