By Francesca Lyon, Lead Nutritionist at FUTURE WOMAN. FUTURE WOMAN is on a mission to fix women’s hormones naturally through a combination of comprehensive, at-home hormone testing and personalised nutrition advice.

As a nutritionist specialising in women’s health, I’ve observed a growing trend that concerns me: the widespread adoption of intermittent fasting without consideration for individual hormonal health or gender. At FUTURE WOMAN, where we focus on evidence-based approaches to women’s hormone health through advanced hormone testing and personalised nutrition plans, we’ve seen firsthand how fasting affects different women in vastly different ways!

The Research Behind Fasting

While the potential benefits of fasting are well-documented in research – from improved metabolic flexibility to enhanced insulin sensitivity and reduced inflammation – there’s a crucial caveat that often goes unmentioned: most studies weren’t specifically focused on women!

This oversight is significant, as we know that women respond differently to men in terms of diet, exercise and stress.

The Female Body’s Unique Response

Research shows that women’s bodies respond differently to energy restriction compared to men’s. When we fast, our bodies are more likely to interpret this as a stress signal, triggering the release of cortisol, our primary stress hormone.

While this might sound harmless, for women already juggling the demands of parenting, work, and household management, this additional stress response can tip the scales from helpful to harmful and (frustratingly!) is actually more likely to result in weight gain, especially around the middle.

Understanding Your Stress Response System

The key lies in what we call the HPA (hypothalamic-pituitary-adrenal) axis – our body’s central stress response system. When this system is already challenged by daily stressors, fasting can trigger a cascade of hormonal responses that actually work against our health goals, potentially leading to:

• Blood sugar dysregulation leading to insulin resistance which can lead to hormone imbalances such as increased androgens which is associated with weight gain especially around the abdomen
• Slowed thyroid production and decreased metabolism resulting in weight gain and changes to hormones like oestrogen
• Downregulated sex hormone production including progesterone
• Disrupted ovulation and menstrual cycles

A disrupted HPA axis can impact nearly all aspects of hormone health and can result in weight gain especially when intermittent fasting is adding more ‘stress’.

It’s also worth bearing in mind that we’re more likely to experience stress in perimenopause, the hormonal shift that precedes menopause, as fluctuating and dropping hormone levels impact our stress response. So, if you’re in your 40s and 50s, your body is even more sensitive to stress! This should be taken into account when we consider if fasting is right for us.

Is Fasting Right for You?

Ideal Candidates for Fasting

The good news is that gentle fasting can be beneficial for some women, particularly those with robust stress management systems. Through our work at FUTURE WOMAN, we’ve identified several key factors that determine whether fasting might be right for you:

• Women with stable energy levels throughout the day
• Those who consistently get adequate sleep
• Women with regular menstrual cycles and consistent ovulation
• Women who aren’t experiencing chronic stress

When to Avoid Fasting

There are some women who should 100% avoid fasting! These are:

• Pregnant or breastfeeding women
• Those under high stress or with high (or very low) cortisol in testing
• Women with irregular or missing periods
• Anyone with a history of eating disorders
• Those following intense exercise programmes
• Women recovering from burnout

Creating Your Personalised Fasting Plan

Starting Safely

If you’re interested in exploring fasting, and you’re one of our ‘ideal candidates’ here’s what we suggest works best for most women:

Start with a gentle approach

Rather than jumping into extended fasting periods, begin with a 12-hour overnight fast. This means if you finish dinner at 8pm, you’d have breakfast at 8am.

This sounds simple, but many women are surprised to find that their eating window is actually longer than they think (late night snacks in front of Netflix anyone?!)

Options to extend your fasting window

If you want to extend this, we recommend bringing dinner forward earlier in the day just a couple of times a week to follow a 10-hour eating window. In my earlier example, this would mean instead of eating dinner at 8pm, have dinner at 6pm instead.

Avoid delaying breakfast as this can disrupt your daily cortisol pattern – the first meal of the day is the most important in terms of signaling to your female body that it’s safe. Remember when our bodies don’t feel safe as women, we retain weight more easily!

Warning Signs to Watch

Listen to your body and watch for warning signs that fasting might be creating too much stress. Common ones we see in practice include:

• Persistent hunger
• Sleep disruptions
• Mood changes
• Energy crashes
• Irregular menstrual cycles
• Spotting before your period
• Weight gain around the stomach

Building Strong Foundations

Before considering fasting, ensure you’re:

• Getting adequate sleep: at least 7-10 hours of good quality sleep a night
• Managing stress effectively: how is your stress? Testing cortisol can be a great way to gain insights into your actual stress levels.
• Eating regular, balanced meals: 3 meals a day with plenty of protein, healthy fats and fibre.
• Maintaining moderate exercise: we never recommend exercising fasted! Your body needs fuel to perform. If you’re someone that follows an intense exercise regime, fasting probably isn’t right for you.

The Power of Hormone Testing

At FUTURE WOMAN, we’ve found that the key to successful fasting lies in understanding your individual hormone patterns, particularly your cortisol levels and daily cortisol pattern. But also your reproductive hormones to see if stress is having a knock on effect on your reproductive health.

Through our Advanced Hormone Test, we can assess whether your body is in a good place to handle the additional stress of fasting, or whether you’d benefit more from focusing on other aspects of health first.

Creating Sustainable Health Habits

Rather than viewing fasting as a quick fix, consider it as just one tool in your health toolkit. For many women, especially parents managing busy households, the focus should be on creating sustainable, nurturing routines that support both immediate and long-term health goals.

The Path Forward

The most successful approach is often the simplest: consistent meal timing, proper nutrition, and balanced exercise, all adapted to your unique hormonal profile and life circumstances. Remember, the goal isn’t to push your body to its limits, but to create an environment where it feels safe enough to feel your best and maintain a healthy weight.

If you’re considering intermittent fasting, start by understanding your hormone health and stress levels. This knowledge will help you make informed decisions about whether fasting aligns with your body’s current needs and capabilities. After all, the best health strategy is one that works with your body, not against it.