Why Intermittent Fasting Isn't the Magic Bullet for Women Over 40

Intermittent Fasting and Time Restricted Feeding - Its impact on Women's Health: What you Need to Know

Intermittent fasting (IF) and time-restricted feeding (TRF) have gained a lot of popularity in recent years, with many claiming it’s the ultimate solution for weight loss and overall health. But is it the best approach for women, especially those over 40, dealing with hormonal shifts, metabolic changes, and the pressures of everyday life? In fact, it could be doing more harm than good.

A Growing Trend, But Still Inconclusive

Although there has been a growing trend and some emerging interest in intermittent fasting, particularly in recent books and online platforms, we’re still lacking comprehensive, long-term studies — especially those focused on women over 40 and 50. The research that does exist tends to be more applicable to men or small sample sizes, and many of the claims are based on theories rather than solid, widely agreed-upon findings.

While fasting may seem like an easy solution, it can be problematic, especially for women who are already struggling with the impacts of restrictive dieting. Let’s explore why.

Skipping Breakfast Doesn’t Equal More Weight Loss

One recent study published in The American Journal of Clinical Nutrition examined the impact of skipping breakfast on weight loss. The study found that skipping breakfast did not result in greater weight loss compared to eating a balanced breakfast. In fact, it suggested that skipping breakfast might actually lead to increased hunger later in the day, which could cause overeating or choosing less nutritious foods. This reinforces the idea that consistent, balanced eating patterns throughout the day are often more effective for weight loss and overall health than restrictive practices like fasting.

Women Are Not Small Men: The Unique Needs of Female Physiology

The idea that fasting works the same way for everyone — including women — is misguided. Dr. Stacy Sims, PhD, a renowned international exercise physiologist and nutrition scientist, has famously pointed out that “women are not small men.”¹ Her groundbreaking work has highlighted the significant physiological differences between men and women, particularly how women’s hormonal fluctuations can affect metabolism, energy use, and recovery.

When it comes to fasting, these differences matter. Most of the research conducted on IF has been done on men, and we simply cannot assume that the results will translate the same way for women. Women’s bodies are more sensitive to energy deficits, and fasting for long periods can interfere with hormonal balance, particularly through perimenopause, menopause, and beyond.

Energy Levels and Exercise: How Fasting Can Backfire

When women restrict their food intake during fasting windows, they often struggle to get the energy they need for exercise. This is especially true for women who train early in the morning, often on an empty stomach. I see it time and time again: women drag themselves out of bed, head straight to the gym, PT session, or even out for a run, only to hit a wall halfway through their workout. They lose intensity, and their performance suffers because they haven’t fuelled their body adequately. This leads to frustration, as they feel stuck in their strength training programs, unable to progress due to low energy and fatigue.

Whether it's PT sessions, high-intensity group classes, or running, lack of energy can lead to quicker fatigue, diminished performance, and reduced stamina. To improve performance, even for those who don't like eating before training, women could consider a small meal or snack before exercising — like a protein smoothie, a banana with peanut butter, or a coffee with added protein and some milk — to ensure they have enough energy to train effectively. This small change can make a significant difference in how they feel during workouts and their long-term progress.

The Hidden Dangers of Fasting for Women Over 40

Many women over 40 are already undereating due to years of following restrictive diets that promote calorie counting and food rules. They may believe that eating less is the key to weight loss, but in reality, they aren't consuming enough to meet their basic calorie and macro needs. Adding IF or TRF to the mix only makes this worse.

There’s a common misconception that most “overweight” women are overeating and consuming large quantities of unhealthy foods. From my experience over 14 years of coaching women, I’ve seen that many women who struggle with their weight aren’t overeating at all. How many of you feel like you’re eating “healthy,” not overindulging on junk food, but still can’t shift that stubborn weight?

Fasting makes it even more challenging for women to meet their calorie and macro needs. Restricting food to a narrow window of 6-8 hours can make it hard to get enough nourishment. This often leaves women with little energy to fuel their day, support their workouts, and their ability to change their body composition. Many women find themselves stuck in the cycle of dieting, restricting calories, and regaining the same weight repeatedly. Fasting exacerbates this issue, further limiting food intake and reducing energy, which ultimately impacts health and performance.

The Role of Autophagy: Exercise vs. Starving

Another popular claim surrounding intermittent fasting is that it promotes autophagy — the body’s natural process of cleaning out damaged cells and regenerating new ones. Many proponents of 'biohacking' (also mostly men) suggest fasting as a way to stimulate this process. While autophagy is indeed important, research shows that it’s actually more effective when we engage in intense exercise. So, instead of relying on fasting to activate autophagy, more intense exercise is a far better way to encourage cellular repair. The combination of proper nutrition and high-intensity training will do far more for long-term health than fasting ever could.

Fasting and the Impact on Hormones

Intermittent fasting can also be a concern for women over 40, especially as they enter perimenopause. During this time, hormonal changes can lead to fluctuating appetite, metabolism, and energy levels. Fasting may cause more harm than good, as it could interfere with the body’s ability to regulate hunger and fullness cues. Women in perimenopause are already dealing with hormonal shifts, which can impact their relationship with food and appetite. Adding fasting into the mix might make it harder for them to get back in touch with their body’s natural rhythms and signals.

In fact, fasting could be turning off hunger, satiety, and appetite signals, and that’s going to take a lot of work to bring back into balance. The longer these signals are suppressed, the harder it becomes to restore a healthy relationship with food and hunger cues. Women over 40 need to focus on nourishing their bodies and supporting their hormonal health — not further restricting intake.

Getting Back in Touch with Your Circadian Rhythm

It’s also important to consider the role of our circadian rhythm in weight management and overall health. Your body has a natural internal clock that aligns with the day-night cycle. Eating within a reasonable time after waking up — ideally within an hour — helps break the catabolic state your body is in after a night of sleep. This can kickstart protein synthesis, support muscle repair, and help regulate metabolism. It also aligns with your cortisol levels, which are higher in the morning, to help you feel energised and ready to take on the day. By eating soon after waking, you help shift your body from a catabolic (breakdown) state into an anabolic (building) state, supporting muscle growth and recovery. The body functions best when we follow its natural rhythm, and skipping meals or fasting for long periods can disrupt this balance, impacting energy and overall health.

A More Sustainable Approach: Eating Earlier in the Night

While intermittent fasting and time-restricted feeding may not be ideal for many women over 40, a gentler approach to fasting can still be beneficial. One way to harness the benefits of fasting without the extremes is by stopping eating earlier in the evening. By allowing your body a 12-14 hour fasting window, you give it time to rest, digest, and repair overnight, which can support metabolic health, improve sleep, and even enhance fat loss.

This approach aligns with the body's natural circadian rhythm, which supports digestion and hormonal balance. Eating your last meal 3-4 hours before bedtime gives your body enough time to properly process food before sleep, potentially reducing the risk of indigestion, improving sleep quality, and helping maintain energy levels for the following day. These benefits can be achieved without extreme fasting, and the key is to make it fit with your lifestyle in a sustainable way. This more sustainable approach:

• Supports metabolic health without disrupting the body's natural rhythms.

• Aligns with circadian rhythms.

• Easier for most people to maintain compared to longer fasting periods.

• Supports better blood sugar regulation.

• Reduces inflammation.

• Promotes fat burning.

Conclusion

Intermittent fasting and time-restricted feeding may sound appealing, but for women over 40, they can cause more harm than good, especially when already undernourished from dieting. Instead of restricting food further, it’s important to focus on nourishing your body with the right balance of nutrients and giving it the energy needed for workouts, recovery, and overall health. Let’s stop chasing trends that might not work for us and focus on long-term, sustainable strategies for wellness.

Are you Ready for Change to Happen?

If you're ready to break free from the cycle of restrictive dieting and fasting, and take control of your health and fitness, I’m here to support you. Whether you're looking for:

• 1-1 Coaching

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• or a complete 12-week transformation with my Thrive Program,

I offer tailored solutions to help you achieve your goals in a sustainable, health-focused way.

Take the first step today and let's work together to build a healthier, stronger version of yourself. Reach out now to learn more about how my programs can help you get the energy, strength, and confidence you deserve!

¹Dr. Stacy Sims is a renowned international exercise physiologist and nutrition scientist with a PhD from the University of Otago, specialising in female athlete health and performance. Her qualifications include:

Ph.D. in Environmental Exercise Physiology, Sports Nutrition MSc in Metabolism - Exercise Physiology

B.A. in Movement & Sport Sciences; Exercise & Fitness

Postdoctoral research at Stanford University