There’s good evidence indicating that intermittent fasting—which involves eating only within a certain limited window of time or eating less every other day—can be an effective way to lose weight, lower your risk for diabetes, and improve other metabolic processes.
Many animal and human studies have shown that fasting helps improve one’s metabolism, lowers blood sugar, enhances brain function, and so much more. However, recently we’ve come to understand that IF works somewhat differently in men than in women, due to differences within hypothalamus function and hormone production.
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While many women can likely still benefit from giving IF a try, especially if they find it helpful to achieve their health goals, it should be done with caution. Women are unique in terms of the ways their bodies respond to blood sugar changes, energy availability, and stress (and yes, fasting can be considered a form of stress). Here are three things women should know when it comes to intermittent fasting.
1. Keep An Eye On Your Blood Sugar
Fasting causes your insulin and blood sugar levels to drop, which can be beneficial if done correctly.
That said, research has shown females have a harder time maintaining blood sugar levels than men. This is largely due to women’s ever-changing levels of hormones, like progesterone and estrogen—and their stronger response to psychosocial stress. Both of these factors can impact insulin sensitivity and thus women’s blood sugar. (Low estrogen levels, for example, can decrease insulin sensitivity.)
For these reasons, it is especially important for women to monitor their levels while practicing IF. Never fast to the point that you feel dizzy or weak, which indicates dramatic blood sugar changes.
It’s also important for women to bounce back from a fast by eating nutrient-dense meals. Focus on including fresh fruits and veggies, high-fiber foods like beans and whole grains, healthy proteins, and fats. Additionally, avoid added sugar, refined grains, and processed foods. Eating this way will promote stable blood sugar levels.
2. Monitor Calorie Intake And Hunger Cues
It’s generally a smart strategy to pay close attention to hunger and fullness cues when eating, avoid snacking between meals, and stay active. However, women should take care to ensure they still meet their overall calorie and nutrient needs while fasting.
Practicing IF may cause a woman to undereat for an extended period of time. If this happens, it’s possible she might deal with side effects such as changes in thyroid function, fatigue, missed periods, metabolic disturbances, increased hunger and/or cravings, and various mood-related issues.
If you suddenly find yourself feeling ravenous and struck by cravings, specifically for highly palatable foods (like those made with added sugar and lots of fat), a drop in hormones like leptin may be to blame. Leptin helps to regulate your appetite and fluctuates based on your body fat and energy intake. A spike in appetite, especially if it leads to binge eating and feeling out of control, can indicate that your body is producing less leptin because it feels under-fueled and wants you to eat more.
If you’re a woman trying IF and start experiencing changes in your energy, focus, or mood, it may be time to up your calorie intake and/or to adjust your eating schedule.
3. Monitor Your Reproductive Health
Undereating (whether overall calories or specific macronutrients) can also trigger changes in a woman’s hypothalamic-pituitary-gonadal (HPG) axis function.
The hypothalamus has been nicknamed the “control center” of the brain. If it receives the signal that the body is not receiving enough calories or certain nutrients, it can respond by signaling to other glands that they should seize producing reproductive hormones, including estrogen and progesterone.
This can result in changes to a woman’s menstrual cycle, such as missed periods, late periods, or anovulation (lack of ovulation). It may also cause women nearing menopause (and already making less estrogen) to experience earlier menopausal symptoms.
Estrogen is needed for not only reproduction, but also for optimal cognition, mood regulation, digestion, recovery, bone metabolism, and heart health. Progesterone, meanwhile, helps with sleep and mood. This is why out-of-whack hormones are an issue you should take seriously.
How Women Can Practice IF Safely
First of all, women with advanced diabetes or who are on medications for diabetes, those with a history of eating disorders, and those who are pregnant or breastfeeding are generally advised against trying IF. In these cases, the restriction and potential hormonal implications involved can be damaging.
Otherwise, fasting can play a helpful role in a woman’s life when it comes to weight management and metabolic health. It seems safe for most women to fast daily for about 12 to 13 hours (such as overnight). Women should be cautious if they decide to fast for longer (14 hours-plus), though.
Even still, it isn’t a good fit for every woman.
Some women seem to be more susceptible to hormonal changes and other issues than others. The best thing you can do is to monitor your own progress and ‘biofeedback’ by paying attention to your menstrual cycle, moods, sleep, and energy levels. As you become more familiar with how you feel, adjust your schedule and diet as needed.
If you want to support blood sugar regulation and metabolic health without full-on fasting, simply limit nighttime eating. Even stopping eating in the three hours before you go to sleep—without changing your morning eating routine—can help you avoid obesity and diabetes.
Dr. Josh Axe, D.N.M., D.C., C.N.S., is a doctor of natural medicine, clinical nutritionist, author, and member of The Vitamin Shoppe’s Wellness Council. Dr. Axe operates one of the world’s largest natural health websites, sharing healthy recipes, herbal remedies, nutrition and fitness advice, and information on essential oils and natural supplements. Dr. Axe founded one of the largest functional medicine clinics in the world, in Nashville, TN, and has served as a physician for many professional athletes.