Intermittent Fasting in Women

Intermittent Fasting in Women: Is it Right for You?

Francesca Lyon, lead nutritionist at FUTURE WOMAN, investigates why intermittent fasting in women could be hindering not helping weight loss, and instead stresses the importance of a stable HPA axis and cortisol levels to achieve a long-term healthy weight.

As lead nutritionist at FUTURE WOMAN, I’ve observed hundreds of women struggling with intermittent fasting as a weight loss approach. While research shows promising benefits overall, the reality for women is far more complex than for men.

So here’s everything you need to know before trying intermittent fasting.

What is Intermittent Fasting?

Intermittent fasting involves structured eating patterns, alternating between periods of eating and fasting. Popular intermittent fasting schedules include:

• Alternate-day fasting (like the 5:2 diet)
• Time-restricted eating (such as 16:8 method)
• Cycle-synced fasting (aligning with menstrual phases)

The Research-Backed Benefits

There are many good quality studies demonstrating several potential advantages of intermittent fasting, including:

• Fat burning and metabolic flexibility: Research shows that there are potential benefits such as accelerated fat burning and improved metabolic flexibility.
• Insulin sensitivity: Research suggests that intermittent fasting may enhance insulin sensitivity and blood glucose management.
• Inflammation and gut health: Fasting has been shown to support better gut health and reduce inflammation which is supportive of reducing the risk of nearly all disease.
• Cardiovascular health: Intermittent fasting has been shown to result in improved cardiac markers, including blood pressure and cholesterol, therefore supporting overall cardiovascular health.

Sounds good, right? Hang on! It’s crucial to note that most research hasn’t focused specifically on women! This matters significantly because women’s bodies respond differently to fasting than men’s.

Let’s take a look at the key differences when it comes to intermittent fasting in women.

Intermittent Fasting in Women: Why it’s Not as Effective

Through extensive clinical observation, we’ve identified that women’s bodies respond very differently to fasting than men’s. While men often thrive on intermittent fasting, women’s bodies are much more sensitive to energy restriction.

When women fast, their bodies typically respond defensively by:

• Entering conservation mode
• Holding onto fat stores, particularly around the abdomen
• Downregulating sex hormone production

It is important that the female body feels safe in order to lose weight. Otherwise, you are actually likely to gain weight when eating less and exercising more, or when intermittent fasting.

Fasting, Cortisol and the HPA Axis in Women

The key difference between intermittent fasting in women vs men lies in how fasting affects our HPA (hypothalamic-pituitary-adrenal) axis as women. Fasting triggers the body to move into survival mode and release stress hormones like cortisol. Research shows that fasting can not only elevate cortisol levels, but also disrupt the cortisol awakening response (the rise in cortisol we experience just after waking), leading to a dysregulated HPA axis that may impact long-term hormone health.

Potential knock on effects to our hormone health from a disrupted HPA axis are significant, and include:

• Blood sugar dysregulation – this can lead to insulin resistance, promoting abdominal weight gain and increasing androgens which can switch off ovulation
• Slowing thyroid production – decreasing metabolism and affecting estrogen levels
• Downregulating sex hormone production – especially progesterone, which is particularly sensitive to stress
• Disrupted ovulation and irregular cycles – ovulation and menstrual cycles can become disrupted

While those with a robust HPA axis may handle fasting short-term, those with existing hormone imbalances and high levels of stress could face a worsening of hormonal symptoms and more weight gain. This might look like irregular menstrual cycles, increased anxiety, low energy, bloating and more weight gain.

It’s worth noting that stress can come in many forms – both internal and external. Of course work, financial and relationship pressures can cause us stress, but also infections, blood sugar dysregulation, nutrient deficiencies, gut dysbiosis and inflammation can lead to dysregulated cortisol patterns. This is why testing is important – many causes of stress are hidden.

Real Life Case Studies of Intermittent Fasting in Women

Let me share two recent case studies from our practice to demonstrate who might benefit from fasting and who might not.

Client A showed poor HPA axis function and low cortisol levels. In this example intermittent fasting is not a good option for her until her HPA axis is much stronger. We recommended adrenal supportive supplements, three balanced and high protein meals a day, one high protein snack in the afternoon and a gentle approach to exercise involving cyclical weight training (where reps are altered depending on menstrual cycle phase) and walking.

Client B, a menopausal woman with robust HPA axis and healthy cortisol levels. Intermittent fasting was appropriate for her as a weight loss tool and she successfully incorporated gentle intermittent fasting to support her weight loss goals. We recommended moving her dinner time earlier 1-2 times per week, and otherwise focusing on a 12 hour eating window.

These cases reveal just a small snapshot of a client’s overall test results, but they show clearly why testing is so crucial before starting any fasting protocol.

My Recommendations for Intermittent Fasting

For most women, I recommend limiting fasting windows to 12-13 hours overnight between dinner and breakfast, rather than the longer windows often recommended to men.

Anything more than this, then it’s essential to test first to assess your HPA axis and cortisol, thyroid activity and overall hormone balance to determine if it’s right for you.

Women Who Should Definitely Avoid Intermittent Fasting

There are certain clients who definitely shouldn’t be fasting! These include:

• Pregnant or breastfeeding women
• Those with eating disorder history
• Anyone following intense exercise programs
• People recovering from burnout
• Those with disrupted cortisol levels
• Women with unaddressed hormone imbalances

Signs that Intermittent Fasting is NOT Working For You

Common signs that fasting is not working for you include:

• Weight gain, especially around the midsection
• Chronic fatigue or low energy
• Sleep disruption
• Mood swings, especially anxiety
• Irregular periods or shortening cycles
• Spotting between periods
• Persistent hunger
• Brain fog
• Bloating

A Better Approach to Weight Loss

Our approach to weight loss at FUTURE WOMAN involves a 360 approach. We want your body to feel safe so that weight loss is easy and long-term. We approach this by ensuring that everything from your hormone levels, detoxification, inflammation and nutrient levels are optimal.

Step 1: Test to Understand Your Body

Here are a few hormone imbalances we’re looking out for in our Advanced Hormone Test to assess the root drivers of any stubborn weight gain or difficulty losing weight. These include:

• High or unopposed oestrogen
• Poor oestrogen metabolism (16-OH and 4-OH pathways in particular are associated with weight gain)
• High inflammation and oxidative stress
• A preference for the 5a pathway (suggesting potential insulin resistance)
• High or low free cortisol levels
• A dysregulated daily cortisol pattern and cortisol awakening response
• Low metabolised cortisol (suggesting potential hypothyroidism)

Step 2: Follow your Personalised Recommendations

In your personalised plan, we’ll interpret your results and make necessary recommendations to support healthy weight loss and hormone balance including:

• Supplements to address any underlying hormone imbalances
• Protein recommendations, including the amounts to aim for at each meal
• Exercise recommendations, with adjustments for cycle phases
• Lifestyle tips to manage stress levels

This combination of targeted and personalised recommendations will allow your body to feel ‘safe’ and make weight loss more seamless and long-lasting.

Conclusion

While intermittent fasting can be an effective weight loss tool for some women, it’s crucial to approach it with awareness of your individual needs and the strength of your HPA axis.

For many women, focusing on consistent meal timing, proper nutrition, and balanced exercise may be more beneficial than strict fasting protocols, especially when they have high or low cortisol due to stress.

If you’re considering intermittent fasting as a woman, or any significant change to your eating patterns, consider first testing your hormones with a comprehensive hormone test like the Advanced Hormone Test to assess if it’s right for you. This will also allow us to address any other underlying hormonal imbalances that may be making it harder for you to lose weight.