Fasted training – is it a good choice for women?

Fasted training is something I see a lot of people doing… it might be because early morning training is the only time available, there is a lack of appetite upon waking or a conscious choice to 'burn' more. But from a nutritionist's point of view, what could the implications be?


What is fasted training? 

Training in a fasted state stems from the idea that training before breakfast, when insulin levels are low, can potentially lead to an increased use of stored fat as energy.
While this might be true, fasted training also increases cortisol levels. Cortisol is also known as the 'stress hormone' and our adrenal glands realise it in response to stressful events such as low blood sugar levels, intense physical effort, intense mental load, illness, etc...

Long fasting periods, fasted training or general undereating are also perceived as stressors by our body, which would increase cortisol levels to cope and stabilise blood sugar levels using liver glycogen reserves. High cortisol levels are also associated with muscle breakdown and slowing of the metabolism – which is not ideal if you are training to improve body composition!

How might this affect women? 

High cortisol levels can also impact female hormonal balance, as both cortisol and female sex hormones (progesterone and oestrogen) share a common precursor molecule called pregnenolone. In situations of stress, the body will prioritise the production of cortisol over sex hormones, leading to potential imbalances such as lack of periods (amenorrhea), fertility issues, and increased or exacerbated PMS symptoms.

Bone health in women is strictly related to oestrogen levels, and as raised cortisol can lower them, it can lead to lower bone density and increased risk of fractures, something we want to avoid when training.

Prolonged elevated cortisol levels might also have an impact on thyroid hormones, reducing their production. When we have lowered thyroid hormone production, we can experience symptoms such as fatigue, weight gain, brain fog, altered body temperature and many more!

Tips to avoid training in a fasted state 

What are the suggestions I give most often to my clients to avoid training in a fasted state? See below:

  • Consider your training time – it will be more productive to train at a different time than forcing yourself to train fasted first thing in the morning! I see many people running every morning fasted, trying to shed weight or getting toned quickly, but a run every other evening will be far more efficient and beneficial for you!
  • If training in the morning before work/school run/life in general is the only option, get organised to have a quick bite to eat handy. Have some chia seeds pudding (keeps up to five days in the fridge), oat cakes with nut butter or a slice of fruit bread.
  • Is the lack of appetite in the morning preventing you from eating? Try to investigate it with the help of a healthcare professional, as lack of appetite and nausea can be indicators of the digestive system or liver unbalances.
  • If fasted training is the only option for you, focus on post-training recovery via a nourishing breakfast/meal complete with all macros (proteins, carbs, fats) as well as micronutrients. A shake or a protein bar on the way to work won’t cut it in this case!

And, of course, if you'd like to know more about fasted training and how to avoid it, you can reach out to a nutritional professional to learn more. We can help you adopt the most suitable training strategies for you and your lifestyle.

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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London, W1S 1HP
Written by Lucia Stansbie, Registered Nutritional Therapist, Dip CNM, mBANT, mCNHC
London, W1S 1HP

Lucia Stansbie, BANT registered Nutritional Therapist founder of Food Power Nutrition

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