Fasted training is one of those fitness phrases that’s been gaining a buzz in recent years. Countless articles and social media posts have extolled the benefits of working out on an empty stomach, claiming that training in this way can enhance performance, encourage fat loss and boost your gains. 

Many fans of early-morning workouts find fasted training more convenient too, because you don’t have to factor in time to eat and digest before rolling out your workout mat. 



But as conversations around the topic of menstruating become more mainstream, the fitness industry is starting to wake up to the role that women’s hormones play when it comes to training and fitness. 

This topic has been largely overlooked because of a gender data gap in health and science data. Currently, only 4% of sport and exercise science studies are exclusively done on women, so all the data available is largely based on the male body. In fact, most mainstream fitness programmes don’t consider the role of female hormones when it comes to training.

There’s now an emerging school of thought that by tapping into fed-state training, women can  boost their athletic performance and avoid a number of serious health issues related to hormone imbalances.

Why could fasted training affect women more than men?

Exercise causes a certain level of stress on the body, which stimulates a hormone response and sets in motion a series of chemical reactions that lead to the adaptive benefits of exercise across the body - from building muscle to better mental health. 

The concern with intermittent fasting is that when it’s paired with high-intensity cardio, it can cause a disruption to women’s hormones and lead to a chronic energy deficiency. 

It all boils down to a neuropeptide called kisspeptin, a naturally-occurring hormone that stimulates the release of other reproductive hormones inside the body. Kisspeptin is closely linked to the release of estrogen and progesterone, as well as the regulation of appetite, energy utilisation and blood sugar balance.




Studies have found that fasted training increases the stress hormone cortisol and decreases the production of kisspeptin, a crucial hormone in the regulation of energy balance in women’s bodies.

As sports dietician Renee McGregor writes: “The levels of cortisol, our stress hormone, are highest in the morning. If you then add further stress to the system by training at a high intensity without any fuel, you can cause cortisol to become chronically high. In turn, [this] can block the hypothalamus and pituitary gland, impacting the production of sex hormones oestrogen and testosterone [which are] important for a number of functions in the body.”

As women have a more increased sensitivity to low energy availability compared to men, they’re at a higher risk of developing a health condition called Relative Energy Deficiency in Sport. RED-S can occur when you don’t get enough fuel through food to support the energy demands of daily training and living. Although women are most affected, the condition can impact anyone of any age, gender or background, although research into RED-S is still in its infancy. 

When there isn’t enough energy available to fuel essential daily functions, on top of training, the body goes into an ‘energy saving mode’. RED-S has wide-ranging adverse effects on all bodily systems and can compromise long-term health and performance for women, leading to cardiovascular issues, weakened immunity, osteoporosis, menstrual disturbances, depression and anxiety. 




What is fed-state training?

Fed-state training is pretty much what it sounds like; when you train after eating. Eating a carbohydrate-based meal before your workout can help to balance your hormones and keep blood sugar levels stable.

Maintaining a steady hormone balance while training can help to avoid the body from going into energy-saving mode, and it could also lead to better athletic performance too.

Crucially, some studies have suggested that fasted training could lead to muscle loss in women. A study on mice who were placed in fasted conditions found that female mice were more likely to deplete their muscle stores over fat and carbohydrates in an effort to maintain their reproductive capabilities. 

And on the subject of fat loss? One study compared 10 women who trained with fasted cardio every day for four weeks to 10 women who had a shake before exercising. The researchers found no difference in fat loss between the two groups of women.



As with most things in health and fitness, there’s no one-size-fits-all approach. If you want to move from fasted cardio to fed-state cardio, it’s about finding the right balance for you. Eat too much, too close to training, it can leave you feeling sluggish. Eat too little and you could disrupt your hormones.

If you don’t want to eat a big breakfast before heading to the studio, you could try grabbing a carb-based breakfast bar to give you an energy boost ahead of your class. But as the gender data gap closes, our optimal nutrition strategy may not just be based on our goals and schedule but our gender too.

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