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Fasting is an ancient method of healing that has been practiced for thousands of years. In modern Western culture we have lost touch with these and other ancient mind-body practices, but fasting is making a comeback due to its health benefits.

You’ve likely come across intermittent fasting and the scientifically-backed 3 day fast to reset your immune system. Fasting may indeed have some benefits, and intermittent fasting can be beneficial for weight loss, but as with all things diet and health-related, there is never a one size fits all panacea. Women especially may want to more carefully consider using fasting as a health tool.

First off: what is fasting? You probably know fasting is willingly withholding food for a determined period of time. Used therapeutically, this is typically one to three days, but mileage varies. Intermittent fasting (IF) is a little different and involves a brief fast of 12-16 hours. Most of us are fasting overnight between dinner and breakfast anyway, but IF is a little more calculated. Some people eat only during an eight hour window during the day; some take a whole 24 fast; and others simply fast for a specific window overnight. It gets way detailed when you go down the IF rabbit hole.

Fasting for 12 + hours each day has promising health benefits. It might help extend your life due to cellular and hormonal benefits. It may also regulate blood glucose levels, control blood lipids, maintain lean mass, and assist with weight loss. (source) It can improve cell turnover, reduce inflammation, and assist with appetite regulation. It could also slow the aging process: During the fasting phase, cells die and stem cells are activated, which starts a regeneration process and gives rise to new, younger cells. (source)

My personal theory is when you give your body a good 12+ hour chunk of time with no food, especially overnight, it’s better able to focus on detoxification and repair. Also, when you’re fasting, your body relies on stored glycogen for fuel, and when that’s exhausted, it uses the only next best of energy: stored fat. You want this if your goal is to lose weight and burn fat.

Regardless, IF may not be the holy grail for everyone.

Intermittent Fasting and Hormones

Keep in mind that our bodies want us to make babies and continue to populate the earth. Women especially have delicate endocrine systems that basically drive us to prevent starvation and excessive stress so we can protect a developing fetus. So you can blame cravings and excessive appetite on biology in many cases, but the roots are in unbalanced hormones. If the female body senses starvation or stress, hunger hormones increase to drive you to chow down. IF can trigger this response in some women.

Our hunger hormones, ghrelin and leptin, tell us when to eat and when we are full. In fact, imbalances in this pair of hormones is one reason people may binge eat or binge eat at night especially. Women are more susceptible to ramped up ghrelin production after fasting, as we discussed above. This can cause binge eating in response to fasting and may exacerbate disordered eating behavior. Fasting or IF can affect thyroid function and fertility in some women, especially if it’s not done properly, done too often, or the woman already has weak adrenals or hormone imbalance.

In fact, studies on rats show that after two weeks of intermittent fasting, female rats stopped having menstrual cycles and their ovaries shrunk. They also experienced more insomnia than their male counterparts (though the male rats did experience lower testosterone production). (source) Human bodies may not perform like rats obviously, but there isn’t yet much research on IF and benefits for women.

Intermittent Fasting and Women

I’ve often steered women away from IF, but I do think it has benefits. The key here is knowing if IF is right for you and how to IF properly for your body. In my experience, IF daily for 14-16 hours works very well for obese women; women who have more than 30 pounds to lose; and women with high blood sugar and high lipids.

Who should not IF: If you have a history of eating disorders, you have hypoglycemia, you have adrenal fatigue or hypothyroidism that’s not yet dialed in, or you’re underweight, you may want to think twice. Women who are pregnant, want to become pregnant, or who have had trouble conceiving should steer clear of IF.

If you’re a woman who is normal weight for your height, or you have 10 or so pounds to lose, the best way to IF is a few non-consecutive days weekly. This means you don’t need to IF every day, only two or three days a week let’s say. You’d fast for 12-16 hours (aim for 14-16), which actually isn’t that difficult. It means you stop eating after dinner at 7pm and then don’t eat anything again until 7am earliest the following morning. Easy, right? You can have water, coffee, or tea, but no milks or sweeteners in these liquids and nothing else.

I myself follow this schedule a few times a week: I finish dinner around 6 or 7pm the previous night. I get up at 7am, and I often work out (burst training, sprints, for 15-20 minutes) in a fasted state to further ramp up fat burning, then eat breakfast around 9-10am. It works great for me and I feel good when I do this. This plan also improves insulin sensitivity.

If you’re a woman and you have more than 30 pounds to lose, you can try IF more often, 5-7 days a week even. You also have the option of fasting one full 24 hour day a week. There are many different options; you just need to see what works for your body.

How Do You Know if It’s Working?

If IF is working for you, you should notice weight loss (if that’s your goal), improved blood sugar balance (works best if you can monitor this with a glucometer), energy boost, good sleep. You feel good.

What to Watch Out For

If you’re trying IF and you notice any of the following, you may need to make adjustments:

• you’re starving and shaky
• IF triggers binge behavior
• you notice a change in your menstrual cycle
• you have missed periods
• you’re otherwise cranky or irritable

If you were going for a full 16 hours, try just 12. If you were doing it every day, try only 2-3 days a week. Make some adjustments and revisit. If it’s still not working, you can add in some adaptogenic herbs to support your endocrine system.

Of course, not everyone needs to IF. But I do recommend at least a 10 hour fast overnight to give your body a chance to repair itself while you sleep. It can’t focus on its night duties when you have a belly full of food to digest. That’s one reason people don’t sleep well when they eat a big meal and go to bed. If you have tired adrenals or hypoglycemia, or you can’t sleep through the night, you may need a small before bed snack to support blood sugar, and that’s a sign that you should work on regulating blood sugar and nourishing your hormones before you can successfully IF.

Have you tried intermittent fasting? Please share your experience!

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Mary Vance, NC

Mary Vance is a Certified Nutrition Consultant and author specializing in digestive health. She combines a science-based approach with natural therapies to rebalance the body. In addition to her 1:1 coaching, she offers courses to help you heal your gut and improve your health. Mary lives in San Francisco and Lake Tahoe in Northern California. Read more about her coaching practice here and her background here.