Intermittent fasting for women: what the research says

By the Luneva team · Published October 17, 2026 · 8 min read

Intermittent fasting means alternating between periods of eating and periods of not eating. The most popular form is time-restricted eating: eating within a daily window, such as 8 or 10 hours, and fasting for the rest. You'll often see it written as 16:8 (16 hours fasting, 8 hours eating).

Much of the early fasting research was done in animals or mostly in men. So it's fair to ask what we actually know about women. Here's an honest summary.

Key points

In studies with many women participants, time-restricted eating leads to weight loss similar to traditional calorie counting, mainly because people eat less.
In women with obesity, studies so far have not found harmful effects on estrogen, progesterone or fertility hormones. Small changes in some hormones have been seen.
Eating earlier in the day may have extra benefits for androgen levels, but the evidence is early.
Fasting is linked to disordered eating behaviours in some young people. It isn't right for everyone.

Does it work for weight?

In a 12-month randomized trial published in the Annals of Internal Medicine in 2023, 90 adults with obesity were assigned to eat only between noon and 8 p.m. without counting calories, to cut calories by 25%, or to make no changes. Both the time-restricted group and the calorie-restriction group lost weight compared with the control group: about 4.6 kg and 5.4 kg more, respectively. The difference between the two methods wasn't significant.¹

In other words, fasting windows seem to work mostly by making it easier to eat a little less. That's useful if a fixed eating window suits your life. It isn't a magic metabolic switch.

A widely cited review in the New England Journal of Medicine describes possible broader benefits of fasting, such as improved insulin sensitivity, but notes that much of the evidence comes from animal studies and short human trials.²

What about women's hormones?

This is the most common worry, and the research is reassuring but limited.

Estrogen, LH and FSH: A 2022 review of human trials concluded that fasting "did not have any effect on estrogen, gonadotropins, or prolactin levels in women."³
Androgens: The same review found that intermittent fasting lowered androgen markers, such as testosterone and the free androgen index, and raised SHBG in premenopausal women with obesity. These effects were more likely when eating was done earlier in the day.³
DHEA: In an 8-week study of women with obesity following a 4- or 6-hour eating window, DHEA, a hormone that's a building block for estrogen and testosterone, fell by about 14% but stayed in the normal range. Testosterone and SHBG didn't change.⁴

The authors of the 2022 review were clear that "very few studies have been conducted on this topic" and that it's hard to draw solid conclusions yet.³ Most studies are short and involve women with obesity, so results may not apply to lean women, athletes or women trying to conceive.

The risks worth knowing about

Fasting is a tool, and it doesn't suit everyone. A Canadian study of about 2,700 people aged 16 to 30 found that, among young women, intermittent fasting in the past year was associated with every eating disorder behaviour measured, including binge eating and compulsive exercise.⁵ That study can't show that fasting causes these behaviours, but it's an important signal.

Warning signs that fasting isn't working for you include:

Thinking about food constantly, or feeling anxious or guilty about eating
Bingeing when your eating window opens
Dizziness, fatigue, poor sleep or irritability that doesn't settle
Periods becoming irregular or stopping

If any of these happen, stop fasting and speak to a doctor or dietitian.

How to fast more gently

Start small. A 12-hour overnight fast, such as 8 p.m. to 8 a.m., is a reasonable starting point. Many people never need more than 14–16 hours.
Eat enough within your window. Fasting isn't about eating as little as possible. Prioritize protein, fibre and regular meals.
Consider an earlier window if it fits your life. Research hints that eating earlier in the day may be kinder to your metabolism.³
Be flexible. Shorten or skip a fast when you're unwell, stressed, training hard, or simply hungry. Many women find they want to eat more in the days before their period, and that's normal. See why you're hungrier before your period.

Luneva is built around this flexible approach. Its default goals range from about 13 to 17 hours, are shorter during and before your period, and are suggestions rather than rules.

A note on safety. This article is for general education and is not medical advice. Intermittent fasting is not suitable for everyone. Please don't fast without talking to your doctor if you are pregnant or trying to conceive, breastfeeding, under 18, have diabetes or take medication that affects blood sugar, or have a current or past eating disorder. If fasting leaves you dizzy, unwell or preoccupied with food, stop and eat.

Track your phases with Luneva.

Luneva estimates your cycle phase from the periods you log and adjusts your daily fasting goal to it, gently and conservatively. Available on Google Play and the App Store.

Sources

Lin S, et al. Time-restricted eating without calorie counting for weight loss in a racially diverse population: a randomized controlled trial. Annals of Internal Medicine. 2023. Summary: ACP Internist Weekly.
de Cabo R, Mattson MP. Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine. 2019;381:2541–2551.
Cienfuegos S, Corapi S, Gabel K, et al. Effect of intermittent fasting on reproductive hormone levels in females and males: a review of human trials. Nutrients. 2022;14(11):2343.
Cienfuegos S, et al. Time-restricted eating and sex hormones in premenopausal and postmenopausal women with obesity. Obesity. 2022. Summaries: UPI, Healio.
Ganson KT, et al. Intermittent fasting and eating disorder behaviours among adolescents and young adults in Canada. Eating Behaviors. 2022. Summary: MDedge.

← All articles