Dieticians are warning women with polycystic ovarian syndrome against using a diet low in grains and high in saturated fat to improve fertility.

Women with polycystic ovarian syndrome are subjecting themselves to risky diet habits in the hope of improving their fertility, according to new research.

Polycystic ovarian syndrome (PCOS), which affects 12 to 21 per cent of Australian women of child-bearing age, is a complex condition that causes hormonal imbalance in women and cysts to grow on the ovaries, affecting their ability to produce eggs.

Most women manage the condition through lifestyle changes, including diet to maintain an optimal body weight to conceive.

But too many are skimping on carbohydrates and overeating fat - putting them at risk of type 2 diabetes, research published in the Nutrition & Dietetics journal has found.

Dr Margaret Hays from the Dietitians Association of Australia says some women with PCOS are overeating fats - the equivalent of a teaspoon more butter a day.

Ms Hays says it's important for women with this condition to reduce saturated fats, found in foods like butter, red meat and the in-trend coconut oil.

She says there is no evidence linking health benefits for women with PCOS to a diet low in carbohydrate-rich grains and high in saturated fats like coconut oil.

The study also showed 61 per cent of the women with PCOS were insulin resistant, compared with 39 per cent of control participants - making it even more important to be adhering to a well-balanced diet.

"To improve fertility and reduce the risk of type 2 diabetes and heart disease, these women need to be choosing good-quality carbohydrates, with a low glycaemic index, and limiting saturated fat.

"If you do have PCOS, eating the right foods, getting regular exercise and maintaining a healthy weight can improve insulin resistance, helping to lower your risk of health problems linked with PCOS," Ms Hays said.