Intermittent fasting has gained a lot of attention and momentum over the last few years and given the reported associated health benefits, we are guessing that you have heard of it! Ema Taylor, a naturopath and nutritionist has observed this momentum in her clinical practice and cautions that as with any health claims, it is most important to consider if this type of diet is right or beneficial for the unique you – particularly for women.

What is Intermittent Fasting?  

Intermittent fasting involves cycling between periods of eating and fasting on alternate days, whole days or set hours in the day. There are different types, such as the popular 16/8 method which involves daily fasts by restricting your eating to an 8-10 hour “eating window”, for example, where you can eat between 12pm and 8pm. An alternate method is the 5:2 method which involves eating 5 days of the week, while restricting calories to 500-600 on two days of the week. 

What are the proposed benefits? 

There are many published articles, from personal blogs to academic journal articles, that document the health benefits associated with intermittent fasting. These include, but are not limited to: 

  • Weight loss and weight management
  • Improved cardiovascular health 
  • Lower risk of diabetes via reducing insulin resistance
  • Improved brain health
  • Reduced inflammation and oxidative stress
  • May prevent cancer
  • May increase lifespan

What does the research suggest? 

While the research broadly demonstrates many positive benefits, the sample sizes tend to be largely limited to men – both male rodents and male humans – perhaps due to their non-cyclical hormones? Human studies have largely been limited to observational studies of religious fasting (such as during Ramadan) with modest sample sizes, that lack in detailing other contributing factors, such as physical activity.

The results that have been found through male samples cannot be simply extrapolated for women, as hormonally we are very different. Out of the numerous studies that I’ve come across, I have found only a few highlighting the potential advantages of intermittent fasting for overweight or obese women, albeit there does not appear to be a solid evidence base for women of a healthy weight. 

For example, a small study on 15 obese women detailed alternate day fasting for 8 weeks resulted in weight loss and a decrease in coronary artery disease risk factors. Whereas in a larger study conducted in 2011 on 107 over weight or obese young women, results demonstrated that intermittent fasting for 6 months was just as effective as continuous energy restriction for weight loss alongside improvements in a number of risk markers for cancer, diabetes and cardiovascular disease. 

A 2012 study conducted on 29 healthy women resulted in a reduction of leukocytes and pro-inflammatory cytokines following intermittent fasting for Ramadan, which is put simply, a positive change. However, a systematic review conducted in 2017 details 9 healthy weight women reported increased feelings of hunger, worse mood, heightened irritability, difficulties concentrating, increased fatigue, eating-related thoughts, fear of loss of control and overeating during non-restricted days, following four weeks of intermittent fasting. This study, although small, highlights the potential disadvantages of intermittent fasting for healthy weight women. 

When should Intermittent Fasting be avoided? 

Women are cyclical creatures and our energy requirements change at different times throughout the month. Ongoing restriction of calories can lead to a number of metabolic issues and there are certain conditions where intermittent fasting should certainly be avoided, these include:

  1. Diabetics and dysregulated blood glucose levels – Having long periods of time without food causes a drop in blood glucose levels that can lead to a potentially life threatening hypoglycemia state for diabetics
  2. Menstrual cycle and hormonal imbalances – Adequate micro and macro nutrients are required for the endocrine system to function efficiently, therefore restrictive eating can lead to hormonal imbalances and irregular menstruation. 
  3. Eating disorders – Most diets are associated with control and restriction, which over time can result in an unhealthy relationship with food. Personally, I don’t like the word diet, as it is usually associated with a short-term way of eating to hit a certain weight goal. I believe a healthier way of eating is sustainable long term and ebbs and flows with our cyclical nature.
  4. Hashimoto’s thyroiditis – Fasting has been shown to reduce thyroid hormones T4, T3 and TSH and to interfere with blood glucose levels, which can potentially be an added stressor on the body for someone in a compromised health state.
  5. Hypothalamic-pituitary adrenal dysfunction and high stress – Research shows that restriction and monitoring of calories increases cortisol levels in females. Prolonged release of high stress hormones interferes with the ability to maintain a healthy weight and has been shown to correlate with centralisation of body fat and obesity.
  6. Pregnant and lactating women – During these periods women require more nutrients to help grow and feed their baby, fasting limits the ability to hit daily requirements while increasing stress hormones. 
  7. Nutrient deficiencies – When calories are being restricted it can be hard to hit our daily micronutrient levels, which over time, can lead to deficiencies that affect our biochemistry. 

Current research shows potential advantages of intermittent fasting for obese and overweight women, however more research is needed to understand the benefits for other subgroups of women. Given our body is actually already well equipped for intermittent fasting – as it benefits from fasting naturally while we sleep each night – does this mean we need to extend these hours to increase the advantages? 

In my clinic, I encourage clients to tune in with their body and take note of how a particular way of eating makes them feel and function, as we are each have unique needs and one diet will never be healthy for everyone. If you’re feeling unsure if it is the right option for you, reach out to your local qualified health professional or nutritionist to discuss your individualised needs.