Would Fasting Over 12 Hours Shrink Your Ovaries?
15 Dec 2025 · 8 min
JJ Virgin and intermittent fasting specialist Cynthia Thurlow address whether extended fasting shrinks ovaries. Thurlow says there's no human research showing this happens, though some animal studies exist. She recommends cycling women fast during the first three weeks of their cycle but skip it in the 5-7 days before their period.
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Chicago, IL Would fasting over 12 hours shrink your ovaries?
This is JJ Virgin, four time New York Times best selling author, celebrity nutrition expert, and Fitness hall of Famer. I've been on a lifelong quest for answers to the toughest health questions and now I'm sharing what I found with you. Welcome to Ask the Health Expert.
Barbie from Instagram asks, would fasting over 12 hours shrink your ovaries? Hey, it's JJ and I've got Intermittent Fasting expert Cynthia Thurlow with me now. Her TEDx talk on intermittent fasting. It's been viewed over 8 million times. So yes, she's a bit of an expert on this subject. In fact, she's my go to expert on this subject. She loves to travel and she's a voracious reader. She reads four to five books at once. Plus, like me, she's a total boy mom. She's got two human ones, although she's got two canine ones too. I've got Daisy Girl. You know, she'll be right back to answer this question, so stay with us.
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I haven't read any research to show that it would shrink ovaries. I know that there's been some research done on lab animals that has suggested that potentially that could be an issue. But we aren't lab animals and I know that that's usually the first step in terms of scientific research. It's done on animals first and then on humans. And so I would just look at it as there are a lot of signs that we need to monitor and look for in terms of fasting to see its impact on our reproductive health. And so if someone is sleeping through the night, their stress is dialed in, they're not over exercising, their energy is good. Then I think women that are still cycling can easily adapt to doing intermittent fasting either on a daily basis or doing every other day or doing one 24 hour fast a week. And then women that are in perimenopause making that transition into menopause in the five to seven years preceding menopause, they can certainly utilize this strategy. But it is easiest for women who are no longer getting their periods because they just don't have that hormonal fluctuation month to month. And you know, one other piece that I think is really important to kind of tack into here is that women that are still getting their periods every month should and can utilize intermittent fasting the first three weeks of their menstrual cycle. So from day one when they start bleeding up until five to seven days preceding their cycle, they can safely integrate intermittent fasting if it's a couple times a week, once a week, etc. However, the five to seven days preceding their periods, they should not be fasting.
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