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Writer's pictureSarah Kim, RD

How Intermittent Fasting Affects Women: Insights and Considerations

As a dietitian specializing in nutrition for women in fitness, I frequently run into questions about intermittent fasting (IF). This dietary approach has gained popularity for its potential benefits, but it's important to understand its specific implications for women, especially in terms of hormonal health and physical performance. In this blog post, I'll share research-backed insights and explain why a cautious approach may be helpful for females.


Understanding Intermittent Fasting and Its Popularity

Intermittent fasting refers to eating patterns that cycle between periods of fasting and eating. Popular methods include the 16/8 method, where eating is restricted to an eight-hour window, and the 5:2 method, which involves normal eating for five days and reduced calorie intake for two non-consecutive days. Advocates of IF claim benefits like weight loss, improved metabolic health, and enhanced longevity. However, these outcomes can vary widely, particularly between genders.


What are the potential downsides of intermittent fasting for women?

For active females, intermittent fasting can pose several challenges:


Blood Sugar Volatility: Women may experience more pronounced blood sugar fluctuations than men during fasting periods. This can impact cognitive function, mood, and physical energy levels—all important considerations for both daily activities and athletic performance.


Impaired Physical Performance: Fasting can significantly reduce glycogen stores, which fuel muscle activity. Reduced glycogen availability can lead to decreased performance and slower recovery, particularly problematic in high-intensity or endurance training.


Digestive Disruptions: Irregular eating schedules can interfere with normal digestive processes, potentially leading to gastrointestinal discomfort such as bloating and irregular bowel movements.


Increased Risk of Disordered Eating: The rigid nature of fasting windows can exacerbate or lead to disordered eating patterns, as it emphasizes when to eat over hunger cues and nutritional needs.


Potential Hormonal Impacts of Intermittent Fasting in Women

Recent studies have highlighted that intermittent fasting can influence female hormone levels differently compared to males. For instance, IF has been shown to decrease androgen markers in women, which might be beneficial for conditions like PCOS but could potentially impact other aspects of health and libido negatively (PMID: 35629915)​.


Additionally, the "warrior diet," an extreme form of IF with a very restricted eating window, has been studied for its effects on hormones like DHEA in women. This hormone, which is linked to estrogen production, was found to decrease during the diet, although it remained within normal ranges. Such changes could have implications for menopausal women and those with breast cancer risk (PMID: 35632892)​


Why a Gender-Specific Approach is Essential

Although new research is getting pushed out, there is still a significant need for a more gender-specific approach in nutrition and fitness. Historically, most fasting research (and fitness/nutrition research in general) has focused on male subjects, which has left a significant knowledge gap regarding its effects on women.


Recommendations for Females with Intermittent Fasting

Despite the current limitations, because of my experience working with female athletes, and the implications that intermittent fasting can have on their overall health and performance, I generally steer clear from intermittent fasting approaches for the majority of my female clients. 


If you’re an active female who might be considering intermittent fasting, read through this article again, for reasons why I, as a registered dietitian, am generally not a fan. I have found that too many individuals resort to intermittent fasting approaches for a quick and easy solution for weight management, and in many cases, it is not sustainable. Plus it can have many negative impacts to overall health and performance, especially for the female athlete. 


Regardless of the approach you are considering, keep the following reminders in mind: 


Consider Individual Variability: Ensure that you are aware of how your body might react differently to intermittent fasting compared to others, especially between different genders.


Monitor Closely: Keep an eye on signs of hormonal imbalance or changes in menstrual cycles, which can be indicators of the diet's impact.


Emphasize Nutritional Balance: Encourage a diet that includes a variety of nutrients to support overall health and hormonal balance, regardless of fasting.


Consult Health Professionals: It is recommended that you discuss any significant dietary changes with healthcare providers, particularly in cases involving reproductive health or hormonal concerns.


Conclusion

While intermittent fasting can be part of a healthy lifestyle for some, it's important for females to approach this method with caution. The potential hormonal impacts, implied by emerging research, suggest that intermittent fasting may not be suitable for all women, particularly those with specific health conditions or hormonal sensitivities.


If you're currently feeling frustrated with your nutrition, or lack of progress in your journey despite working out hard in the gym, click the link here to schedule a free 30 minute nutrition assessment with All-Tru's head coach. In this we'll uncover what and when you eat in a day and give you simple nutrition and lifestyle adjustments so you can lose body fat while maintaining or gaining strength (and without having to restrict food ;).

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