Diet And PCOS

An estimated one in four women has polycystic ovaries, but many cases are mild so that, overall, around one in 20 women develop symptoms known as polycystic ovary syndrome (PCOS). PCOS is the most common hormone disorder among women of reproductive age, and a leading cause of infertility. Many of the symptoms of PCOS can be improved by diet, exercise and supplements.

Symptoms of PCOS

Polycystic ovary syndrome is a condition in which the ovaries enlarge to between two and four times their normal size, and are covered in multiple tiny cysts. Symptoms of PCOS can include:

  • lack of regular ovulation
  • scanty or absent menstrual periods
  • oily skin
  • acne
  • excess unwanted hair
  • Difficulty conceiving.

Not every woman affected develops every symptom. Overall, around one in two women with PCOS become overweight, for example, with fat mainly deposited around the waist.

What causes PCOS?

The ovaries normally produce small amounts of androgen (male) hormones, such as testosterone, as well as the female hormones, oestrogen and progesterone.

If the ovaries produce too many androgen hormones, this blocks the normal, monthly development of egg follicles. The pituitary gland in the brain responds by producing more luteinising hormone (LH) to kick-start the ovaries which stimulate growth of more follicular cysts. As a result, the ovaries enlarge and become covered with multiple small cysts containing under-developed eggs.

PCOS is associated with a metabolic abnormality in which the cells become less responsive to insulin hormone. Insulin is made in the pancreas gland and is needed for glucose to enter muscle and fat cells, where it is used as a fuel. If cells don’t respond to insulin properly, blood glucose levels become higher than normal and women with PCOS are seven times more likely to develop glucose intolerance and diabetes than women with normally functioning ovaries.

Researchers now believe that it is insulin resistance that drives high levels of testosterone in PCOS, rather than the other way round. As a result, women with the worse symptoms of PCOS tend to be overweight as carrying excess fat is one of the underlying causes of insulin resistance – quite simply, overstuffed fat cells stop responding to insulin as they don’t want to handle yet more glucose and convert it into yet more fat.

Insulin resistance might also explain why many women with bulimia often show evidence of PCOS – even if they are of normal weight. Ovarian changes associated with bulimia are thought to result from large fluctuations in blood glucose levels that occur between starving and bingeing which reduce the effects of insulin.

Losing weight improves PCOS

In women with polycystic ovary syndrome, weight loss can improve insulin resistance, androgen levels, glucose tolerance, heart disease risk factors such as high blood pressure, ovulation rates and your chance of conception.

The optimum level of weight loss appears to be 5% or more of body weight (eg around 5kg if you weigh 100kg), but even short periods of calorie restriction can decrease androgen levels and restore normal luteinising hormone secretion and menstruation in some women.

Weight loss also restores the balance between two hormones involved in regulating appetite, leptin and ghrelin. Leptin is produced by fat cells (adipocytes) to reduce hunger and energy intake. Leptin is now also known to help regulate fertility, so decreasing leptin levels by losing weight may partly explain why even modest weight loss can increase the chance of conception.

Eating 200 kcals per day less than you need will prevent weight gain and promote slow weight loss in the long-term.

Eating 500 kcals per day less than you need will cause the average person to lose around 0.5kg per week.

Eating 1,000 kcals per day less than you need will cause the average person to lose around 1kg per week.

How many calories do you need?

The number of calories (kilocalories) you need is based on your age, weight and level of activity.

For lean, healthy women, the following calorie intake is recommended, based on your level of activity.

Age (years)


Moderately active


19 – 30 2,000 kcals 2,000 – 2,200 kcals 2,400 kcals
31 – 50 1,800 kcals 2,000 kcals 2,200 kcals
50 and over 1,600 kcals 1,800 kcals 2,000 – 2,200 kals


Women who are overweight have a greater calorie requirement but, as women with PCOS may find it harder than average to lose weight, let’s not factor this in.

Sedentary is equivalent to just carrying out activities of daily living with lots of sitting around eg 3000 – 5000 steps per day.

Moderately active is equivalent to walking 1.5 to 3 miles per day at a reasonable pace (3 to 4 miles per hour) eg taking around 7,500 steps per day

Active is equivalent to walking more than 3 miles per day at a brisk rate eg achieving your 10,000 steps per day on most days.

Using a fitness tracker to set goals such as steps per day can help you boost your activity level to make weight loss easier.

Using the above values, and assuming you are moderately active, then following a diet that provides between 1,200 and 1,500 kcals per day should, theoretically mean you lose weight.

If only it were that simple.

As explained in my post on low fat versus low carb diets, a calorie obtained from eating carbohydrate has different metabolic effects than a calorie obtained from fat or from protein.

Cut back on carbohydrates to lose weight

When you have insulin resistance, cutting back on carbs is likely to make it easier to lose weight. A lower carb, low glycemic diet therefore works best for women with PCOS.

When it comes to weight loss, the results of 15 studies found that a low carbohydrate diet helped women with PCOS to lose between 1% and 5% more weight compared to other weight loss diets.

carpaccioIn one study, for example, 96 overweight women with insulin-resistance followed either:

  • a high-carbohydrate, high-fibre (low fat) diet
  • a high-fat Atkins Diet
  • or a high-protein Zone Diet.

After a supervised 8 week weight loss phase and an 8-week weight maintenance phase, reductions in body weight, waist circumference, triglycerides and insulin levels were significantly greater in those following the high fat or high protein diets than in the standard high carb, low fat diet.

When compared with the high-carbohydrate diet, those on the high-fat diet lost 2.8kg more weight, and also lost significantly more fat (as opposed to muscle) overall (5.2kg fat versus 3.9kg). As a result, they lost 3.5cm more from their waist circumference, too.

When compared with the high-carbohydrate diet, those on the high-protein diet lost 2.7kg more weight, and lost 2.7cm more from their waist.

LDL-cholesterol levels decreased in those following the high-carbohydrate and high-protein diets, but tended to fluctuate in those on the high fat diet. This study suggests that a reduced-carbohydrate, higher protein diet is the best overall approach to reduce PCOS symptoms and the risk of cardiovascular disease and type 2 diabetes.

Dietary carbohydrates and PCOS

Eating carbohydrate triggers the release of insulin – the very hormone that is contributing to PCOS. Insulin acts as the key to let excess circulating glucose into muscle and fat cells, where it is burned as fuel (muscles) or converted into fat for storage (fat cells).  Excess dietary carbohydrate is also converted into triglyceride fats in the liver and sent out to the fat cells for storage.

Reducing your intake of carbohydrates reduces your production of insulin and helps to minimise the effects of insulin resistance. This approach will help, whether or not you are taking the anti-diabetes drug, metformin, which also improves insulin resistance, reduces weight gain and lowers testosterone levels in women with PCOS.

Glycemic load and PCOS

Following a very low carbohydrate diet, such as Atkins, doesn’t suit everyone, and is controversial. You will also benefit from following a lower carbohydrate diet that is not quite so extreme.

The effect of different foods on blood glucose levels is measured by its glycemic load (GL), which is defined as the amount of carbohydrate present multiplied by the glycemic index (GI). A diet with a high glycemic load increases insulin resistance and is associated with worsening symptoms of PCOS and an increased risk of diabetes.

Reducing the glycemic load of your diet can reduce insulin resistance and help you lose weight as well as reducing symptoms and improving fertility.

When comparing the diets of women with and without PCOS, researchers have found that following diets with a high GI or GL and a low fibre intake is significantly associated with polycystic ovary syndrome.

Researchers investigated the effects of a lower carbohydrate/higher fat diet against a higher carbohydrate, low fat diet in women with PCOS who were very overweight (BMI 39) and had insulin resistance.

Although both diets provided the same number of calories, replacing dietary carbohydrate with healthy fats (monounsaturates and polyunsaturates such as omega 3s) reduced insulin concentrations by 30%, compared with when the same women followed the higher carbohydrate, lower fat diet.

The researchers concluded that ‘this simple and safe dietary intervention may constitute an important treatment for PCOS.’

How to follow a low GI diet for PCOS

A low GI is effective for weight loss as long as it provides fewer calories than your daily requirement. A low GI diet is also suitable for weight maintenance if you don’t need to lose weight.

Following a low glycemic diet involves cutting back on carbohydrates and eating more foods that supply protein and healthy monounsaturated and omega-3 fats such as fruit, vegetables, nuts, seeds, fish, lean meats and wholegrains.

Don’t overdo the wholegrains, however, as even though they have a relatively low glycemic index, a high intake of wholegrains can contribute to weight gain and also stimulates hunger and carbohydrate craving.

Avoid refined carbohydrates (white or beige carbs such as white bread, pasta, white rice, potatoes, cakes, biscuits, and other carbohydrate-laden baked goods) which promote insulin production.

Cut right back on sugar – check labels to select foods with the lowest level of added sugar.

This low GI way of eating is similar to the Dietary Approaches to Stop Hypertension (DASH) eating plan that was originally devised for people with high blood pressure.

The DASH diet is also helpful for reducing insulin resistance. In a study involving 48 overweight women with PCOS, half followed the DASH eating pattern, which focuses on fruit, vegetables, wholegrains, low-fat dairy products and is low in salt, saturated fats, cholesterol, refined grains and sweets. The other half followed a control diet which provided the same overall level of protein (18%), fat (30%) and carbohydrate (52%) but from sources that were not low-glycemic.

After 8 weeks, those following the DASH diet had significantly lower insulin levels than those following the control diet, and lost significantly more weight from around the waist (5.2 cm loss versus 2.1 cm in those on the control diet) and hips (5.9 cm loss versus 1 cm in controls).

Click here for more information on the DASH diet.

Dietary fats and PCOS

When cutting back on dietary carbohydrates, your relative intake of fats will increase. Researchers have found that a reasonable increase in total fat intake, of up to around 40% of energy intake, does not have a major impact on insulin sensitivity in people with metabolic syndrome (a similar condition to PCOS in which there is insulin resistance).

Concentrate on obtaining healthy fats such as omega-3s (eg from oily fish and walnuts) and monounsaturates (omega-9s from olive oil, macadamias, almonds and avocado) rather than omega-6s which promote inflammation and, to keep your doctor happy, watch your intake of saturated fat (although the evidence that saturated fat is harmful is far from clear-cut).

Dietary protein and PCOS

When cutting back on dietary carbohydrates, your relative intake of protein will inevitably increase, as explained in my post on low carb versus low fat diets.

Research shows that a higher intake of protein can improve insulin responses and glucose tolerance.

A high protein, low-calorie diet also helps to preserve muscle so you lose weight as fat rather than lean tissue and improves blood glucose levels.

A higher protein intake also increases satiety, helping you to eat less overall, and stimulates metabolism to increase the amount of energy given out as heat.

Comparison of high-fat and high-protein diets with a high-carbohydrate diet in insulin-resistant obese women.

Lifestyle approaches

Take regular exercise as this burns glucose and fatty acids, boosts your metabolic rate to aid weight loss, and improves insulin resistance in muscle cells to improve most PCOS symptoms.

If you smoke, do your utmost to stop, as smoking damages the ovaries enough to trigger a menopause at least two years earlier than normal.

Supplements for PCOS

Supplements that have shown beneficial effects on polycystic ovary syndrome include the following:

Agnus castus

Artichoke extracts



Co-enzyme Q10

Evening primrose oil

Folic acid

Milk thistle



Omega-3 fish oil

Saw palmetto

Soy isoflavones

Vitamin D


Which nutritional approaches have you found most helpful for PCOS? Please share your experience via the comments below.

Image credits: pixabay; shutterstock

Please leave a comment or ask me a question ...