Is a Low-Carb Diet Beneficial for PCOS?

There is no good evidence that one type of diet is superior to another for women with polycystic ovarian syndrome (PCOS). Some research shows women with PCOS can benefit from following a low-carbohydrate or low-glycemic index (GI) diet, which can aid in managing weight loss and reducing the risk of diabetes. However, another study showed that a high protein/low carb diet and a low protein/high carb diet were equally effective for weight loss, improvement in insulin resistance and menstrual cycles in women with PCOS. A study in adolescents showed no difference between a low glycemic load or low-carb diet and a low-fat diet.

More Regular Periods

A 2010 study published in the American Journal of Clinical Nutrition found that women with PCOS who followed a low-GI diet had better insulin sensitivity, more regular menstrual cycles, and higher quality of life scores than women who didn't.

The study included 96 women aged 18 through 40 who were diagnosed with PCOS. Women who were taking metformin were still eligible, though women who had diabetes or depression were excluded from the study.

The women were assigned to follow either a low-fat, low-GI carbohydrate diet (50 subjects) or a low-fat, healthy diet with moderate to high GI carbohydrates (46 subjects). Subjects were followed for one year or until they lost 7% of their body weight.

While all participants reached their weight loss goal, 41% of those who followed a low-GI diet and 50% of those who followed a regular GI diet failed to reach that goal within the specified one-year goal. Women who took metformin in addition to following a low-GI diet had significantly higher improvements in their glucose tolerance testing as well.

Weight Loss and Improved Insulin Sensitivity

A small 2015 study in the Journal of Obesity and Weight Loss Therapy found that women with PCOS who followed both a low-starch and low-dairy diet were better able to lose weight, improve their insulin sensitivity, and reduce testosterone levels in the short term.

The study included 24 women who were overweight or obese who followed a diet low in carbohydrates and dairy products for 8 weeks.

At the end of the study, the women lost an average of 19 pounds, reduced their body mass index, and lost about 3 inches from their waist circumference. In addition, the women saw a reduction in insulin levels and insulin resistance measures, as well as a reduction in testosterone levels.

The researchers noted that while carbohydrates are the main stimulators of insulin release, dairy products and starches result in higher post-meal insulin secretion than non-starchy vegetables and fruits. In addition, high levels of insulin are believed to increase androgen levels in women with PCOS.

Given the study was only 8 weeks long, the long-term sustainability wasn't measured and more studies are needed to determine if people can sustain such a diet long-term and also what its long- term affects are in women with PCOS.