I want to start this post off by saying I’m obviously not a woman, and that female body is highly complex and more complicated than the male body. I’ve gotten a lot of questions about Intermittent Fasting (IF) from female clients in the past as it’s a very popular dietary method. I obviously can’t clearly discuss any personal experiences as to IF from a female perspective, but I can discuss it based on the academic research that exists – as it’s a very popular dietary method.

The personal training market is more favored more toward women hiring personal trainers than men, so if you’re a male Fitness Trainer like myself, the likelihood that you’ll be working with female clients is higher than not.

In short, IF is the practice of going for prolonged periods without eating. Here’s some things to know/look out for before deciding to try IF. I’ve linked the article I made this infographic from on IF for women in my sources, which you can find below, and the article here. In that article, it will go through additional academic information, as well as links to additional sources located at the bottom of that same article. I highly encourage that you read it in addition to reading this article as this blog post will give a synopsis and layman’s view on IF for women.

There’s evidence that IF—when done properly, in the right people—might help:

• regulate blood glucose
• control blood lipids, like triglycerides
• reduce the risk of heart disease
• manage bodyweight
• help you gain (or maintain) lean mass
• reduce the risk of cancer

Now at the same time current evidence indicates that some women who practice IF can have

• Disrupted metabolism
• Increased cramps
• Higher risk for binge eating
• Higher risk for early onset menopause.

This overall causes a disruption in hormones production which in turn affects ovulation, metabolism and mood.

Why is this? What role does GnRH play and what is that?

Hormones are sensitive to energy intake for women when it comes to fasting, some women do fine with IF and others don’t do well at all. Part of this is due to the hypothalamus (an area in the brain that releases hormones) releasing Gonadotropin-releasing hormone (GnRH) as part of the hypothalamic-pituitary-gonadal axis, more commonly known as the HPG axis.

• GnRH stimulates follicle-stimulating hormone (FSH), and luteinizing hormone (LH). FSH, LH in women triggers the production of estrogen & progesterone for ovulation.
• GnRH production can be thrown off by fasting and can create hormonal disturbances that effect the cycle through a protein molecule called Kisspeptin. Kisspeptin acts as a regulator of GnRH production in men and women and is sensitive to leptin, ghrelin, and insulin (satiety regulating hormones), and what we do know is that women produce more kisspeptin than men so when kisspeptin is thrown off balance it will disrupt the whole monthly cycle.
• Prolonged fasting can negatively impact Kisspeptin and hinder GnRH production. This can impact the female reproductive system negatively. One example is missed periods. It does get more complicated than this based on many factors.

Do the foods you eat while you’re IF have a role in whether you can stick to it or not? 

Women generally speaking eat less than men do, meaning that when it comes to protein they’ll typically eat less protein because they’re eating less overall. This is more so the case when you’re fasting. This can be problematic given that protein provides amino acids (building blocks of protein), which are critical for the reproduction process.

When amino acids levels are too low, it negatively impacts your insulin-like growth factor (IGF-1) levels and estrogen receptors. Both are needed during the menstrual cycle to thicken the lining of the uterus. If the uterus lining doesn’t thicken, an egg can’t implant, and pregnancy can’t occur. Hence, low protein-diets can reduce fertility.

What other roles does estrogen play?

In the brainstem, estrogens modify the amino acids that signal to your brain that you feel full (cholecystokinin) or hungry (ghrelin). In my previous articles “Why We Overeat”, and “How to Stop Overeating For Good” I go into greater detail as to how the hypothalamus regulates our hunger through the vagus nerve which connects the GI tract to the brain.

In the context of estrogen, the hypothalamus also stimulates neurons that halt the production of appetite-regulating amino acids. Meaning, if we change the activity which makes your estrogen to drop (like fasting), chances are you’ll find yourself feeling a lot hungrier—and eating a lot more—than you would under normal circumstances.

So in a nutshell, IF for women is a lot more complicated than it appears due to the fact that women are more sensitive to changes in energy balance.

Here’s some examples of how IF might play out throughout the lifecycle.

Adolescence and Teenager Years:

• Fasting is not recommended during this part of the lifecycle. Rapid growth is occurring physically, and emotionally. Young children can self-regulate their appetite quite well at this point in life as long as nutritious food is being given by the parent. When teenage years body image becomes more of an issue and can lead to unnecessary dieting when it isn’t appropriate. The importance of self-love and creating a stress free relationship with food during this stage is really important as a parent. This is done through appetite awareness and ensuring there are healthy options rich in whole foods are readily available for your teenager.

When you want to have kids: 

• In short, IF when you’re trying to get pregnant is not a good idea. I wouldn’t recommend this for the reasons listed earlier in the article, even if you need to lose weight prior to getting pregnant, unless it’s recommended and supervised by your physician that you do so. There are many other dietary protocols to choose from that allow for a moderate reduction in calories that don’t require fasting. Unless you’re getting paid based on appearance, doing competition prep or a professional athlete you shouldn’t look into IF as your first dietary option to lose weight.

What about if you’re already pregnant or if you’re recently postpartum?

• It’s still a no go here. You and the baby need as much nutrition as possible. It would be detrimental to your babies development and your physical health during this time. Not only is a stressful time and a big adjustment to your life, extra nutrients are needed to facilitate your body staying in homeostasis and to feed your child. If weight gain during/post pregnancy is a serious concern for you, always consult your physician to get your first clearance for a return to exercise. This is usually done around 6 week mark.
• If you’ve just given birth then fasting still isn’t recommended at this stage, as you and the baby still need extra nutrients. Taking a moderate; not a fast approach to weight loss is the healthier, and more sustainable option.
• Strength training, along with walking, moderate step climbing, and the stationary bike for cardio are great options while pregnant. In addition, maintaining and building isometric core exercises are essential to keeping a healthy spine strong while pregnant. Avoid machine based work that doesn’t keep your spine in a neutral position.

IF when you’re aging?

Aging naturally leads to a desire to focus on health for both women and men alike. As of now, there isn’t quality research available on whether or not intermittent fasting is beneficial to women who are pre or post menopause.  Yet, estrogen production is still lower which doesn’t interfere with the reproductive processes as much, however there are still considerations that must be accounted for (hot flashes and the intensity of them). Here’s some general rule of thumb metrics to consider if you’re thinking of fasting in this life stage:

• • You’re living life in a position of low stress
  • You get good sleep
  • No nutrient deficiencies
  • You don’t have intense hot flashes.

So with all this being said, if you decide that you still want to IF, and calorie restrict there’s a lot of ways to not eat. Here’s the most popular one’s below:

• 16:8: Don’t eat for 16 hours, and consume your meals in an 8 hour window.
• 18:6: Don’t eat for 18 hours, and consume your meals in a 6 hour window. Shorter feeding window.
• 14:10: Don’t eat for 14 hours, and consume your meals in a 10 hour window. Longer feeding window. This is a more realistic option for if you’re looking to restrict calories without altering the portion sizes of your other meals.
• 20:4: Don’t eat for 20 hours, and consume your meals in a 4 hour window. Shorter feeding window.
• 36 hour fasts: You don’t eat for 36 hours
• Eat Stop Eat: You eat normally, and fast for 24 hours 1-2x out of the week on non-consecutive days.
• Meal skipping: You consume a meal but don’t eat at another normal feeding time. Simply stated, it might look like this: Eat at breakfast, skip lunch, eat dinner.

Finding a method that works for you is critical if you decide to fast. If you decide that fasting is the right method for you, start with shorter duration and consult your health professionals (i.e. physician, dietician or health coach beforehand.)

IF works, but it isn’t for everyone, listen to your body!

Source: 

“Does Intermittent Fasting Work for Women?” Precision Nutrition, 10 Feb. 2021, www.precisionnutrition.com/intermittent-fasting-women.