I'm a women's personal trainer and here’s why I am actively against intermittent fasting and training fasted in women.

Ashlee

Hi, my name is Ashlee! I am a Southampton based Female only Personal Trainer & Coach. I have worked with 100+ women to help them live a healthier and more active lifestyle whilst reaching their fitness, physique and confidence goals. As I exclusively work with women, I am very interested in Women’s Health and developing my knowledge to best help my clients.

Something I have discovered on my journey, that many coaches may still actively promote, not understanding the risks. Is that fasting techniques utilised in fat loss scenarios such as intermittent fasting and training in a fasted state, pose a unique risk to women’s health. I am actively against the habitual use of these methods as women in the name of weight loss. In this blog I’d like to explain why in the hopes that this may help even just one woman.

What is fasting?

Fasting is often presented as a wellness practise/trend. There are many ways of practising fasting. Fasting refers to restricting food intake by not eating for certain periods of time. These methods are often utilised as weight-loss or weight management techniques, sometimes as methods for certain health benefits. Fasting for religious or cultural reasons is not related to the topic of discussion today.

Intermittent fasting is one method, where a person may go for sustained periods without eating food. It is practised by cycling periods of eating and fasting. For example, only eating during specific windows of time such as between the hours of 12-6pm or not eating for 16 hours of the day etc. Of course we naturally ‘fast’ during sleep, hence break-fast as the first meal of the day.

Intermittent fasting is often used as a weight loss method. It works by reducing your eating window and can be beneficial for fat loss simply due to reducing your calorific intake by reducing the time you are able to consume calories.

I personally do not believe in any quick fix methods to fat loss. The ONLY way you can lose fat is through a calorie deficit, it is simple science. Any complicated or quick diet technique will simply somehow/someway, put you in a calorific/energy deficit. As a female personal trainer, all of my clients will take a balanced approach to fat loss if they choose to have that goal and be educated on this.

Other supposed benefits outside of weight loss are blood sugar, pressure and cholesterol control, reduction of chronic inflammation and cognitive benefits. There

is currently no robust evidence underpinning the supposed benefits of intermittent fasting in non obese individuals. The practice of fasting also inherently goes against the needs of female physiology and can cause or enhance disordered eating.

A Note on The Research Gap

It is important to note that, more than 90% of all sports science research including that of the ‘evidence’ of fasting benefits, is based off of male research subjects. There is a massive disparity and underrepresentation of women in research studies (thats a whole other blog post in and of itself). It is important to highlight this when we are talking about sport science topics in relation to women and the impacts on women’s health.

What we do know is that women are NOT little men. We have completely different physiologies to men and the most important factor is that men do not have a menstrual cycle. You may have heard this before men run on a 24 hour cycle whereas women run on an individualised (typically) 28 day cycle when it comes to our hormones. This impacts a lot more than you may think. We are inherently different to men and there is not enough research done yet to show how significant this is. We do have to take male focused ‘evidence’ from studies with a pinch of salt as women in this case.

Most nutritional advice we are presented with even if it is ‘evidence based’ is taken from research based on men. Fasting, in particular training whilst fasted, works really well for male physiology but it is not as effective in women. In fact it can have potentially harmful impacts to us.

So, you may be thinking Ash if there’s not enough research how can you tell us not to fast? What little research we do have shows the negative risks of fasting on women’s reproductive hormones and menstrual cycle!

Training Fasted?

Research shows that men respond really well to fasted training. It has been popularised based on the initial research that training in a fasted state caused better endurance adaptions as we were more likely to use fat stores as opposed to carbohydrate stores during exercise. However, women’s bodies are already great at burning fat during exercise! Research does indicate that women utilise fat as energy more readily than men during exercise, especially at moderate intensities. The supposed benefit for men of training fasted therefore does not apply to us as women anyway.

Further research has also since demonstrated that training fasted can actually yield twice the amount of muscle breakdown than training in a non fasted state decreasing both muscle mass and strength over time. Fasted training can have a negative impact on how much and how hard you can train. As we increase in intensity we use carbohydrates as fuel (both men and women), as its the quickest

way to make energy available during exercise. If there are no carbs to pull from your exercise intensity will suffer. Therefore the general cons as women in particular far outweigh the pros.

The impact can be far more detrimental to women’s hormones. Training fasted creates a state of low energy availability. As women, it is important that we maintain a consistent energy source available, particularly carbohydrates for our hormone health and signalling. Research demonstrates that periods of low energy availability such as when we train in a fasted state, are enough to cause menstrual dysfunction by interrupting the release of your reproductive hormones. This has significant consequences on your health and ability to train and perform at your best. The disruption of our menstrual cycles has a knock on effect to not only our reproductive health, but immune function, bone health, mental health and general fitness and wellbeing. This risk should not be downplayed or ignored!

Hormonal disruptions can in the short term impact your cycle of course causing irregular cycles. It can also impact your mood, stress levels and mental health, elevating both anxiety and depression. It can disrupt sleep, exacerbate fatigue and cause low energy. As well as aesthetic problems such as hair loss, acne and struggles with weight maintenance. Prolonged disruption to your menstrual cycle can lead to infertility, increase your risk of cancer, cardiovascular disease and osteoporosis.

This is not to say that on the odd occasion perhaps necessity that you absolutely can never train fasted. It is just not recommend to make a habit out of it. Ideally refuel after your workout if you do ever need to train fasted. If you regularly opt to train fasted primarily due to training first thing in the morning and waiting to eat breakfast until after, opt for a quick source of carbs perhaps a banana or rice cakes before training. Then have your protein packed breakfast after training to refuel. As active women, you should be aiming to eat at least every 3 hours whilst awake and maintain a balanced diet.

Whilst I’m actively advising you to not utilise fasting methods or any quick fix fat loss methods to help you lose weight. That is not to say there are not healthier methods out there to do so. I recommend that you seek professional advice from a coach like myself to support and guide you without detrimenting your health.

Thanks for reading, Ash xo

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