Intermittent fasting (IF) has gained popularity for its potential benefits, including weight loss, improved metabolism, and better overall health. However, while some thrive on this eating pattern, it may not be suitable for everyone—especially women of reproductive age or those under high stress. Hormonal balance, cortisol levels, and metabolic responses vary between individuals, making IF more beneficial for some than others. In this post, we’ll explore when intermittent fasting works best, who should approach it with caution, and how to determine if it’s the right fit for your health.

In more recent years a lot of clients and students have asked me about Intermittent fasting (IF). This way of eating involves a cycle of measured time between periods of eating and fasting, with several different methods to choose from, such as the 16:8 (16 hours of fasting, 8 hours of eating). While some benefit hugely with weight loss, improved metabolism, and better overall health, intermittent fasting might not be suitable for everyone, particularly women of reproductive age or for people who are highly stressed.
Within Systematic Kinesiology we help clients with their diet on a daily basis which has a profound effect on improving their health and allowing symptoms to drop away, this may include suggestions about when to IF and when it may best be avoided.
Female hormones, particularly oestrogen and progesterone, are finely tuned to a woman’s menstrual cycle. These hormones fluctuate throughout the month, which plays a vital role in regulating everything from mood and energy, to fertility and metabolism. Introducing fasting, especially extended periods into this delicate balance can have unintended consequences.
Stress Hormones, Cortisol and Intermittent Fasting
One of the biggest concerns with intermittent fasting for women is its impact on cortisol (the body’s main stress hormone). IF can elevate cortisol levels, and in women this can disrupt the balance of oestrogen and progesterone, leading to irregular cycles, mood swings, and even issues with being unable to get pregnant.
When we don’t eat for long periods of time, it causes the body to release cortisol to keep our blood sugars stable. If our blood sugars get too low, we would eventually die. Therefore, when we fast regularly we overly activate our stress response. This would be fine if it was the only stress our body had to deal with, but when we have so much other stress in our lives already, then intermittent fasting just becomes another stress on the body. Read ‘Cortisol Friend or Foe’ here.
Insulin Sensitivity, Blood Sugar Levels and Intermittent Fasting
While IF has been shown to improve insulin sensitivity in many people, women may experience different metabolic responses. Because there is so much more going on inside women’s bodies they may be more sensitive to fluctuations in blood sugar levels, especially if they are fasting during times of hormonal changes (like during menstruation or in the luteal phase). This can then lead to energy dips, cravings, and overeating when the fasting period ends.
Impact of IF on Women’s Reproductive Health
For women who are trying to conceive, intermittent fasting might disrupt ovulation and menstrual cycles. This is particularly true for women who already have irregular cycles or conditions like polycystic ovary syndrome (PCOS), where hormonal imbalances are common. Prolonged fasting can reduce fertility by lowering the production of hormones that are required for ovulation. Therefore, with hormones already disrupted, it may be good to avoid. However, we can of
course help support and balance hormones, fertility and PCOS in other ways with Systematic Kinesiology.
Adrenal fatigue and Intermittent Fasting
If we have adrenal fatigue or burnout, then intermittent fasting is going to burn our system out more. Intermittent fasting is more suitable for people with good adrenal function and a resilient stress response because then it can cope with the stress of not eating. However, for a lot of people, and I see many clients in this situation, intermittent fasting ends up being counterproductive rather than beneficial.
When and What Not to Eat
Most people skip breakfast and eat their first meal around 12 noon. However, the best meal to skip for metabolism is dinner (the meal we eat in the evening). It is also a good idea to avoid wheat, milk, refined sugars and salt/slaty snacks (Himalayan and Celtic is great) which further helps to keep inflammation down.
When Intermittent Fasting May Be a Good Idea
Despite the above, intermittent fasting does have a place and can still have many benefits, especially in specific circumstances:
- Men:
For men intermittent fasting can be beneficial for improving insulin sensitivity, promoting fat loss, and also boosting testosterone levels. Men’s hormonal fluctuations are less dramatic throughout the month compared to women’s, which means they are less likely to experience the same negative side effects from fasting unless they are highly stressed. Fasting often has a positive impact on men’s metabolic health too, including reducing inflammation, improving cholesterol levels, and enhancing brain function. - Post-Menopausal Women:
Post-menopausal women, whose estrogen levels have significantly declined, may find intermittent fasting beneficial in certain situations. Without the fluctuating hormone levels that pre-menopausal women experience, post-menopausal women are less likely to face the hormonal imbalances that intermittent fasting can sometimes trigger. Additionally, fasting may help with weight management and reducing the risk of conditions such as heart disease, diabetes, and obesity, which are more prevalent in post-menopausal women. Research has shown that intermittent fasting can help manage blood sugar levels and improve metabolic health, both of which are important considerations as women age, as long as they are not in adrenal fatigue/burnout. - Women with Specific Health Goals:
For women who are not actively trying to conceive or experiencing significant hormonal fluctuations, intermittent fasting may be helpful for managing weight or improving metabolic health. Women with conditions such as obesity or type 2 diabetes may benefit from intermittent fasting when guided by a healthcare professional, as it can improve insulin sensitivity, regulate blood sugar, and promote fat loss.
Is Intermittent Fasting Right for You?
Intermittent fasting can be a powerful health tool for many people although it’s best to approach it with caution—particularly for women with active reproductive cycles and anyone who is highly stressed. Interestingly our blood group can also be a significant factor too. Blood groups O & B can do very well with long periods with no food while blood groups A and AB often do better grazing.
Ultimately, intermittent fasting is best when personalised. It is a good idea for women with concerns about how fasting may affect their hormones to consult a healthcare provider before making any significant dietary changes. By understanding the body’s needs and making adjustments accordingly, both men and women can enjoy the benefits of intermittent fasting while maintaining a healthy hormonal balance.
For help with male and female hormonal balance, find your nearest Systematic Kinesiologist on our online register.