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Published: May 21, 2013 | Updated: May 22, 2013 By Kristina Fiore , Staff Writer, MedPage Today

Action Points

• Note that this crossover study demonstrated an improvement in various metabolic factors, including testosterone levels, among women with PCOS while on a carbohydrate-restricted diet.
• Be aware that HDL cholesterol levels were improved on the low-carbohydrate diet, despite the higher fat content.

Lowering carbohydrate intake may reduce insulin levels and, subsequently, testosterone, which could mitigate symptoms for women with polycystic ovary syndrome (PCOS), researchers found. In a small crossover study, women with the disease who cut back on carbs saw significant increases in insulin sensitivity (P<0.05) and dynamic beta-cell response (P<0.001), Barbara Gower, PhD, of the University of Alabama at Birmingham, and colleagues reported online in Clinical Endocrinology.

Those changes were associated with a 23% reduction in serum testosterone (P<0.05), they added. ”

A moderate reduction in dietary carbohydrate reduced both insulin and testosterone,” Gower told MedPage Today. “There is no reason not to recommend reduction in dietary carbohydrate, particularly processed carbohydrate, for women with PCOS. It may have tremendous benefit, and there is certainly no downside.”

About 6% to 10% of women have PCOS, which is defined by hyperandrogenism, ovulatory dysfunction, and polycystic ovaries. Many of these women also have insulin resistance, hyperinsulinism, and metabolic dysfunction — which stimulates androgen production, which, in turn, produces many features of PCOS.

Researchers have hypothesized that reducing insulin through dietary means may ultimately diminish testosterone, thereby alleviating some symptoms of the condition.

Gower and colleagues enrolled 30 women in a crossover trial in which they were given one of two diets over each 8-week period, with a 4-week washout in between.

The “standard” diet derived 55% of energy from carbohydrates, 18% from protein, and 27% from fat. The low-carb diet derived just 41% energy from carbohydrates, 19% from protein, and 40% from fat.

They found that besides increases in insulin sensitivity and beta-cell response, the lower carbohydrate diet was associated with significant decreases in basal beta-cell response (P<0.001), fasting insulin (P<0.001), fasting glucose (P<0.01), HOMA-IR (P<0.001), and total testosterone (P<0.05), compared with the standard diet.

Despite the higher fat content of the lower-carbohydrate diet, patients’ lipid profile improved significantly on this diet, the researchers wrote. The standard diet, on the other hand, led to declines in HDL cholesterol and increases in the total-cholesterol-to-HDL-cholesterol ratio.

When all data were combined, reductions in testosterone were significantly associated with the decline in fasting insulin, basal beta-cell response, and insulin area-under-the-curve (AUC) (P<0.05).

“These data suggest that in hyperinsulinemic women with PCOS, modest reduction in dietary carbohydrate in the context of a weight-maintaining diet may reduce fasting insulin and ultimately lead to a decrease in circulating testosterone,” they concluded.

Gower also noted that the reductions in insulin parameters also signal a reduction in diabetes risk.

The study was limited by the broad age range of the participants and by the small sample size, which didn’t permit subgroup analysis based on glucose tolerance status.