Intermittent Fasting for Improved Performance for Women and Men by Julia Glanz


In recent years, Intermittent fasting has become extremely popular - and for good reason.

There has been exciting findings and strong evidence supporting the positive outcomes of IF and how it can be used as a sustainable strategy for:

-       Weight loss[1]

-       Lowering inflammation[2]

-       Improving digestion[3]

-       Increasing fat burning[4]

-       Reducing insulin (your storage hormone)[5]

What is intermittent fasting?

Intermittent Fasting (IF) is a term used to explain an eating pattern where you cycle between periods of eating and periods of fasting (abstinence from food and caloric beverages). The therapeutic benefits have been documented for thousands of years and have shown that this way of eating is deeply rooted in our biology. 

Philosophers like Socrates, Hippocrates, Plato and Paracelsus even believed in the health benefits of regular fasting. 

Not only was fasting used as a remedy to heal our body, but it was something our body became accustomed to back in the day when there were times of food scarcity. Our body has evolved to become accustomed to regular fasting. 

However, nowadays with constant availability and easy access to food at all hours, we as a country have started to consume more than our body can tolerate. This has resulted in a spike of chronic diseases such as metabolic syndrome (ie. Obesity, time 2 diabetes, heart disease, abnormal lipids and high blood pressure).

With the increasing evidence that has come out supporting IF for health benefits, you may be wondering if it’s right for you, and more specifically if it can enhance your physical performance.

The IF protocol that will be referenced in the remainder of this article is a 12:12 - 18:6, meaning that your fasting window is between 12-18 hours and your eating window is between 6-12 hours (the remainder of the day).

How can IF help your performance?

It’s important to note that any performance benefits that come from practicing intermittent fasting will depend on your bio-individuality, current state of metabolic efficiency and of course other dietary and lifestyle factors. With that being said, here is an overview of how this practice may be supportive for improving energy substrate utilization during exercise and at rest. 

After an overnight fast, your insulin levels are low. One of insulin’s main roles is to store glucose. When insulin is high, your body is in storage mode and therefore not mobilizing fat for fuel. When insulin is low, your body can start tapping into fat burning mechanisms (lipolysis). Additionally, in a fasted state, your body’s cortisol levels are increased. In the presence of cortisol, when insulin is low, lipolysis is increased in adipose tissue.[6]

Your body only has a limited supply of stored glucose, which gets depleted overnight in the liver and depleted in muscle during exercise. Therefore, when training in a fasted state, your body switches from using primarily glucose to fat. Your body’s ability to switch substrates for energy is known as metabolic flexibility.

When exercising, the extent of which your body uses one versus the other depends primarily on the intensity and duration of exercise as well as what is readily available. While exercising in a fasted state, skeletal muscle uses both fat and glucose to support higher energy demands while lipolysis (fat burning) is also enhanced in adipose tissue.

In addition to burning fat for fuel, there is another hormone at play that may support your performance goals, too.

During a fasted state is growth hormone is increased.[7] Growth hormone helps preserve muscle mass, which is obviously supportive for many reasons as it pertains to performance as well as resting metabolic rate and overall health for your future self. 

Takeaways and considerations:

In addition to its health benefits, intermittent fasting can promote metabolic efficiency, enhance fat burning, all while preserving lean mass. While this may not increase your one rep max, it may increase your capacity to do work, lower insulin (your storage hormone) levels and provide additional anti-inflammatory benefits. 

It’s important to note, however, intermittent fasting and fasted workouts should be used as a tool in your toolbox and not be something you do daily. The reason for this is because, just like when programming for exercise, you want to give your body a stimulus, let it adapt, change the stimulus, and repeat. There are also other lifestyle factors (ie. stressful periods in your life or a time where your body has increased energy demands such as ovulation/before menstruation) where intermittent fasting may not be appropriate. It’s important to speak with your health practitioner before beginning any diet/way of eating or exercise protocol to determine if it is right for you.

If you’re a female and interested in learning more about how to sync your menstrual cycle with intermittent fasting, your diet, and exercise routine, click here for my Intermittent Fasting For Women Ebook & Masterclass.


Disclaimer: This article is not intended for the following: Women who are pregnant, trying to get pregnant, or breastfeeding; individuals dealing with low energy availability or low testosterone, individuals with T1 diabetes, advanced diabetes, on medication, or have a history of disordered eating and/or eating disorder.


Intended readers of this article are strongly cautioned to consult with a physician or other qualified health care professional before using any of the information or engaging in any of the activities contained in this program. No exercise or nutritional program materials can substitute for professional care or advice. Consult with a health care provider concerning any possible adverse effects which may result before using any of the information contained in this article. Extreme caution is urged when using the information contained in this article. The article author is not engaging in rendering medical advice or services. This article is for educational purposes only.

By: Julia Glanz






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