The hidden dangers of intermittent fasting for menstruating women

Intermittent fasting is one of the most popular diets/lifestyle choices, boasting many benefits – but could it be doing more harm than good for women of menstruating age? In this article, I delve into the pros and cons of intermittent fasting, and provide guidance on how to approach it safely.

My thoughts on intermittent fasting is the number one thing I get asked when people discover I’m a nutritionist.

Here is my possible unpopular opinion

I do not believe it is the magic pill for weight loss that people claim it to be, especially for women of menstruating age. If not done correctly, fasting can cause many more issues than any health benefit it is touting.

Fasting has been around for thousands of years. Many cultures incorporate fasting for spiritual reasons. It has become popular in the last ten years – one of the latest ways to be healthy, look your best and usually a tool for weight loss.

One of the major draw cards for fasting is its simple to implement. You don’t have to worry about removing food groups or sticking to strict calories – all you need to do is choose a fasting window.

Intermittent fasting, the basics

Intermittent fasting involves cycling between periods of eating and abstaining from food within designated eating windows. Opting for nutrient dense foods and hydrating when fasting. These eating patterns include time-restricted, twice a week, and alternate day fasting, with popular methods such as:

A 2023 meta-analysis compared the above fasting protocols to calorie energy restriction, finding alternate day fasting the most effective for weight loss, followed by calorie energy restriction. However, these were short-term studies with compliance dropping after 3 months. Read my article here for sustainable weight loss strategies. 

In contrast, a 12-month study was involving 100 African American women compared alternate day fasting, calorie restriction & a control group maintaining their usual habits. Both diet groups experienced similar weight loss percentages. However, the alternate day fasting group exhibited a significant increase of low-density lipoprotein (LDL) cholesterol, a risk factor for heart disease and strokes. The study also observed a significant dropout rate in the alternate fasting group, with participants citing dissatisfaction with the diet.

Lets go through the benefits for women

Weight loss – While intermittent fasting may result in weight loss, it does not necessarily outperform other dietary strategies.

Decreased diabetes risk – Intermittent fasting has shown promise in reducing the risk of diabetes by enhancing insulin sensitivity. However, research in this area is relatively recent, and preliminary findings suggest potential benefits in improving metabolic health.

Heart health – Intermittent fasting has been linked to improved heart health by reducing inflammation, blood pressure, and blood fat levels. While many of these findings are derived from rodent studies, they suggest potential benefits for human heart health.

Improved cellular health – a 2019 review  revealed that during fasting, cellular repair processes are activated. This is associated with longevity, reduced inflammation, lowered cancer risk, and improved metabolism. However, it’s important to note that these findings are primarily based on rodent studies, and further research is needed to understand the implications for females.

It is not clear if changes in the above markers are due to fasting, or overall energy (calorie) deficit.

Reproductive health
Women and men experience different impacts on their hormonal systems. Calorie restriction affects the hypothalamus – located deep inside your brain, linking the nervous system and endocrine system. This disruption can lead to hormone imbalances, causing irregular periods, weakened bone health, and infertility. Although limited studies on women exist for intermittent fasting, rodent studies confirm prolonged calorie restriction affects menstrual cycles. 

Stress & bone health
Stress plays a crucial role in weight regulation and menstrual cycles. Women’s bodies are more sensitive to stressors, like prolonged fasting & calorie restriction.  Intermittent fasting, amidst modern life stressors (physiological, environmental, and emotional), can exacerbate these effects. Adding fasting to an already busy schedule might do more harm than good.

Elevated cortisol levels from fasting may lead to fatigue, muscle loss, blood sugar irregularities, insulin resistance, and thyroid dysfunction over time. This can impact metabolic rate, growth, and development, potentially leading to weight issues and other health concerns. Long term elevated cortisol can cause increased blood pressure, plaque build-up in artery walls, bone & muscle deterioration, diabetes, and immune suppression.

Disordered eating
Intermittent fasting may trigger overeating or cycles of restriction and bingeing, particularly in individuals with a history of disordered eating. Those with high body dissatisfaction and a desire for weight loss may resort to severe restriction methods. Caution is advised, as intermittent fasting can negatively affect individuals with a history of disordered eating.

Further side effects
Hunger
Mood swings
Headaches
Low energy
Lack of concentration
Overeating in non-fasting days
Constipation

Avoid intermittent fasting if;
You have irregular cycles
You are not sleeping enough
You are not eating enough
You don’t eat consistently
You have thyroid issues
You have a history of eating disorders
If you are stressed

How to fast safely

If all the above do not apply to you, there are ways you can incorporate fasting into your week. The key is to go slow.

Look at your current eating times – note when you stop eating at night and when you eat in the morning. Look to reduce the eating window by 1hr, then 2hrs. You do not need to fast every day; you can do it 1-2 times per week. Health markers have been shown to improve in a 10-12hr fasting window. You don’t have to aim for a 16 or 18 hour fast.

For example, stop eating at 7pm and have breakfast at 7am = 12hr fast. Completely achievable.

Remember it is not about skipping meals. You still want to eat three balanced meals in your eating window.

I recommend bringing your dinner earlier than pushing out your breakfast. Cortisol is at its highest in the morning, if you are exercising in the morning or are stressed in any way delaying your breakfast will increase your cortisol levels and as a result make you more stressed.

I always recommend eating within 60mins of waking to avoid this.

Key points 

Intermittent fasting is not suitable for everyone

If you are a woman of menstruating age please fast with caution

Don’t skip meals when you fast 

If fasting stop eating earlier at night, rather than later in the morning

If this has got you thinking more about your health and would like 1:1 guidance then I’m here to help. You can book a free 15min call to see if we’re a good match or jump right in and book an initial consultation here.

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As always, we are aiming for progress, not perfection and small sustainable changes.