A 6-hour eating window led to weight loss and improved hormonal markers in overweight or obese women with polycystic ovary syndrome. Digest
Polycystic ovary syndrome (PCOS) affects about 1 in 5 women of reproductive age and is often difficult to treat, particularly when it comes to weight loss and hormone balance. In a new randomized trial, researchers tested whether time-restricted eating (TRE) could improve body weight and metabolic health in PCOS patients without requiring calorie counting.
The study included 76 overweight or obese women aged 18 to 45 with PCOS. For 6 months, one group ate only between 1 p.m. and 7 p.m., one group followed a diet meant to reduce daily calorie intake by 25%, and a control group kept its usual diet while eating across more than 10 hours per day.
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When compared directly with each other, both diets had similar effects, although some outcomes appeared more pronounced for one diet than the other relative to the control group:
- Body weight fell by about 3.5% with TRE and 3.8% with calorie restriction (CR) from the start of the study, while it increased by 0.9% in the control group.
- Both intervention groups also reduced fat mass and waist circumference, while lean mass (mostly muscle and other nonfat tissue) changed little.
- Visceral fat (the deeper abdominal fat stored around internal organs) showed a clearer decrease in the CR group, although this effect was not consistent across all analyses the researchers performed.
- Total testosterone dropped in both intervention groups. However, TRE had a more pronounced effect on the free androgen index, a measure that estimates how much biologically active androgen is available to body tissues.
- Both diet strategies lowered fasting insulin and HOMA-IR, a commonly used estimate of insulin resistance.
- TRE also reduced HbA1c, a marker that reflects average blood sugar over about three months, while CR more clearly lowered fasting glucose and improved QUICKI, an estimate of insulin sensitivity.
- Common PCOS-related symptoms and risk factors, including irregular cycles, excess hair growth, acne, oily skin, elevated blood pressure, and abnormal blood lipid levels, did not differ clearly between groups. In a follow-up analysis, participants who lost at least 5% of their body weight had slightly more regular menstrual cycles.
These findings fit with a central biological pattern seen in PCOS. Excess body fat, especially visceral fat, can worsen insulin resistance. In turn, high insulin levels can stimulate the ovaries to produce more androgens, such as testosterone, and can reduce production of sex hormone-binding globulin, a blood protein that binds testosterone and limits how much of it is active. Elevated androgen levels can disrupt ovulation and contribute to common PCOS symptoms. Both diets improved insulin- and androgen-related measures, suggesting better hormonal regulation. However, these improvements did not translate into clear changes in clinical symptoms. This may be because the weight loss was only modest, and prior studies suggest that at least 5% weight loss may be needed to improve PCOS symptoms.
The study lasted only 6 months and food intake was self-reported. However, for women with PCOS who find daily calorie tracking difficult to maintain, a fixed eating window may offer a simpler option worth considering. In this clip, I discuss with Dr. Layne Norton the benefits, limits, and longevity impacts of time-restricted eating and calorie restriction.