Time-restricted eating improves hormone levels in women with PCOS

Polycystic ovary syndrome, or PCOS, affects as many as 18% of all childbearing-age women. The condition occurs when a woman's body produces too much of a group of hormones called androgens, chiefly testosterone. Menstrual irregularity, obesity and even infertility can result.

The first line of treatment is typically hormonal birth control, said UIC professor of nutrition Krista Varady. But there can be negative side effects to mood, libido and metabolism, plus an increased stroke risk in some people, Varady said.

We're looking for other ways of lowering testosterone levels in these women. One way is through weight loss. If someone loses around 5% of their body weight, they can actually help lower testosterone levels and sidestep any kind of drug intervention."

Krista Varady, UIC professor of nutrition 

A new study led by Varady tested how one weight-loss method - intermittent fasting - affects hormones and symptoms in patients with PCOS. Published in Nature Medicine, the research shows that restricting eating to a six-hour daily window decreased testosterone without negatively affecting female hormones. The study also showed that weight loss through calorie counting decreased testosterone. 

However, some critics of intermittent fasting have posited that the diet disrupts female hormones, Varady said.

"There's a particular sentiment that intermittent fasting is really bad for women." This is untrue, she said. "This study and several other studies published by our lab and others show that intermittent fasting can actually improve female hormone levels, particularly in women with PCOS." 

Varady and her colleagues studied a type of intermittent fasting called time-restricted eating. In this method, you eat only during a set six- or eight-hour period each day. During the remaining 18 or 16 hours, you fast with calorie-free beverages and water until the next day. 

Simply put, the strategy helps people eat less, Varady said. So does counting calories, a method Varady and her colleagues tested alongside intermittent fasting in the study. But intermittent fasting had some additional benefits.

"It's a way of reducing energy intake without having to do really complicated calorie counting," she said about intermittent fasting. Varady and others have shown in previous work that eating only during an eight-hour window can cut around 300 to 500 calories a day.

In addition to obesity and insulin resistance, which raise risks of diabetes and heart disease, PCOS can cause ovarian cysts, acne and facial hair growth.

In a group of 76 pre-menopausal women with PCOS, the researchers tested how outcomes differed after six months between time-restricted eating between 1 and 7 p.m. daily and calorie counting. Both diet schemes ended up cutting participants' intake by about 200 calories per day, the team found, leading to average weight loss of about 10 pounds over the six months.

Both groups also experienced a decrease in testosterone concentrations. But only time-restricted eating reduced free androgen index, the ratio between testosterone and the protein that transports it through the blood, which is a marker of how much active testosterone is reaching a body's tissues. It also improved A1C levels, a risk marker for diabetes, Varady said.

Though intermittent fasting did not lessen other PCOS symptoms, like menstrual period irregularity, Varady suggested those symptoms might improve with longer time on the diet and greater weight loss.

About 80% of the participants in the time-restricted eating group said they were going to continue the diet, Varady said.

The study was a team effort among nutrition professors in the department of kinesiology and nutrition in the College of Applied Health Sciences. Sofia Cienfuegos designed and ran the study with Varady, while Kelsey Gabel, Lisa Tussing-Humphreys and Vanessa Oddo collaborated as well.

"We all have a keen interest in women's health, and we designed this together and ran it together," Varady said. "It was one of the biggest nutrition department collaborations we've ever done."

Other UIC authors on the study include Sarah Corapi, Mary-Claire Runchey, Jodie Lyons, Maria Alonso de Leon, Vasiliki Pavlou and Mark Ezpeleta from the College of Applied Health Sciences; Julienne Sanchez from the College of Medicine; and Shuhao Lin, formerly of UIC and now with the Mayo Clinic.