A time-restricted eating program — consuming all meals between 1 p.m. and 7 p.m. without tracking calorie intake — promoted greater weight loss in women with polycystic ovary syndrome (PCOS) than no intervention, according to a randomized controlled trial published in Nature Medicine.
The results suggest time-restricted eating can promote weight loss and potentially alleviate symptoms in women with PCOS, an endocrine disorder that affects nearly 1 in 5 women of childbearing age and is the most common cause of infertility in young women globally.
“We know that the inflammation and insulin resistance that characterize PCOS can make it harder for people with PCOS to lose weight, so it’s an important finding that time-restricted eating is safe and effective for weight loss in people with PCOS,” said Shaina Alexandria, PhD, assistant professor of Preventive Medicine in the Division of Biostatistics and Informatics and a co-author of the study.
Women with PCOS commonly experience increased androgen levels, primarily testosterone, in addition to irregular or absent menstrual periods, abnormal ovulation, changes in hair growth, acne and enlarged ovaries that may also contain cysts. The cause of PCOS is currently unknown, but women with a family history of PCOS or type 2 diabetes have a higher risk and up to 70 percent of women with PCOS have obesity and, as a result, low-grade inflammation.
A mainstay of PCOS is insulin resistance — when cells throughout the body improperly respond to insulin, which helps move glucose from the blood into cells to use for energy. This causes the pancreas to overproduce insulin to balance out glucose levels and, in response, drives excess androgen production (hyperandrogenism).
Current treatments for PCOS include oral birth control pills and metformin, which is commonly used to treat high glucose levels in patients with type 2 diabetes. However, these treatments can increase a patient’s risk of developing mood disorders such as depression, as well as gastrointestinal issues and blood clots.
Weight loss has been shown to help reduce androgen levels and insulin resistance, improve menstrual function and help improve fertility in patients with PCOS.
Time-restricted eating regimens — limiting eating to a 6-to-8-hour time window without counting calories — has been shown to be an alternative weight loss option for patients with PCOS as it eliminates the need for daily calorie tracking, which can cause patient frustration and dissatisfaction that stunts weight loss.
In the current study, 76 women with PCOS were randomly assigned to one of three groups for six months: a six-hour time-restricted regimen (all meals consumed between 1 p.m. and 7 p.m. without calorie tracking), a calorie restriction plan (reducing daily calories by 25 percent) or a control group with no dietary changes.
Participants received regular nutrition counseling from a dietitian throughout the six-month trial. The primary endpoint was a percent change in body weight after six months.
By month six, body weight had significantly decreased in the time-restricted group (-4.32 percent) and the calorie restriction group (-4.66 percent) compared to the control group. No serious adverse events were reported across all groups.
The investigators also found that blood glucose (HbA1c) levels decreased in the time-restricted group, but not in the calorie restriction group. Total testosterone levels were also reduced in both groups.
Additional findings included the following:
- Fasting glucose decreased in the calorie-restriction group only, relative to controls.
- Fasting insulin and insulin resistance were reduced in the time-restricted eating and calorie restriction groups relative to controls, with no difference between the groups.
- Insulin sensitivity increased in the calorie-restriction group only, relative to controls.
The results suggest that time-restricted eating without calorie counting may be a promising alternative strategy compared to daily calorie counting to lower body weight, hyperandrogenism and insulin resistance in women with PCOS.
“We found evidence that other factors on the pathway from diet to weight loss — including changes in insulin markers and androgens — also improved in response to time-restricted eating. We also didn’t find any evidence in this study that participants changed their diet quality, which leads us to believe that the effect of time-restricted eating in this sample was due to calorie restriction and not other changes in diet you might expect given the diet counseling part of the intervention,” Alexandria said.
Krista Varady, PhD, professor of Kinesiology and Nutrition at the University of Illinois, Chicago, was the senior author of the study.
This work was supported by the Department of Kinesiology and Nutrition at the University of Illinois, Chicago.
