The Myth of Fasted Training for Women: Why It’s Not the Fat-Burning Shortcut You Think
For years, the idea that training fasted leads to greater fat loss has circulated in the fitness world. While it may sound appealing, especially for those practicing intermittent fasting, the reality is far more complex—particularly for women. Let’s break down why fasted training isn’t the magic bullet for fat loss and why fueling properly before workouts is critical for women’s health and performance.
Intermittent Fasting and Women’s Metabolism
Intermittent fasting is often praised for its ability to improve metabolic flexibility—enhancing insulin sensitivity, reducing blood sugar levels, and lowering cholesterol. However, women naturally have more oxidative muscle fibers than men, which already makes them more metabolically flexible.
Oxidative fibers are the muscle fibers with the greatest aerobic capacity, meaning they allow for sustained, low-intensity activity. This gives women a natural advantage in endurance-based exercise and energy efficiency. But because of this, women don’t necessarily gain the same metabolic benefits from fasting as men do.
The Stress Factor: How Fasting Affects Women Differently
While intermittent fasting may seem like a way to burn fat efficiently, it actually places additional stress on the female body. This is because fasting increases cortisol, the body’s primary stress hormone.
Without adequate fuel, women are unable to train at high enough intensities to trigger essential post-exercise responses such as the release of growth hormone and testosterone. These hormones are crucial in lowering cortisol levels and promoting recovery. In essence, fasting before training keeps women in a prolonged state of stress, which can negatively impact performance and recovery.
Hormonal Disruptions and Kisspeptin’s Role
One of the biggest reasons fasted training affects women differently lies in the brain’s Kisspeptin system. Kisspeptin is a hormone that regulates other reproductive hormones.
Men have one area of Kisspeptin neurons in the brain, while women have two.
In women, one Kisspeptin region controls appetite and luteinizing hormone (LH), which regulates endocrine function and releases hormones into the bloodstream.
The second Kisspeptin region controls estrogen and thyroid function.
When women start the day without food, they disrupt their appetite signals, LH, estrogen, and thyroid function—leading to potential long-term hormonal imbalances. Adding caffeine on an empty stomach further spikes cortisol, keeping the body in a heightened state of fight-or-flight (sympathetic nervous system activation). This can lead to metabolic dysfunction and fatigue over time.
Why Eating with Your Circadian Rhythm is Key
Fueling your body in alignment with your circadian rhythm (your body’s internal clock) is essential for brain function, cognitive performance, and thyroid health. Instead of fasting, women should aim to eat strategically to support their metabolism and workouts.
That said, fasting can still be a useful tool for metabolic conditions such as obesity, PCOS, or inactivity. However, for women who are active, especially those engaging in high-intensity training, fasted workouts are more likely to hinder performance than enhance it.
The Impact of Fasting on Women in Perimenopause
As women enter their 40s and beyond, they experience increased hormonal fluctuations, including elevated baseline cortisol levels, lower levels of estrogen and progesterone. During perimenopause, estrogen levels decline, which is significant because estrogen plays a key role in strength and power—similar to testosterone in men.
If women train in a fasted state, they won’t be able to reach the intensities needed for effective high-intensity interval training (HIIT) or resistance training.
A fasted HIIT workout will feel like a moderate workout instead of an intense one.
During strength training, if a woman is supposed to lift at 80% of her 1 rep max, she may only be able to reach 75-78% due to lack of fuel.
For women in perimenopause, lifting heavy is crucial for maintaining strength and preventing muscle loss. Training in a fasted state diminishes the ability to fully activate the central nervous system, making it harder to gain strength and power.
How Women Should Train Throughout Their Life Cycle
Women’s training needs evolve as they age, and understanding these shifts can help optimize performance and longevity:
20-40 years old: Focus on hypertrophy, performing as many reps as possible, or going to failure to build muscle efficiently.
40-60 years old: Shift to strength training, focusing on gaining and maintaining lean mass. Train heavier as the nervous system starts to weaken with age.
Additionally, understanding the menstrual cycle can help optimize training:
First half of the cycle (Day 1 (first day of bleeding) - Ovulation): This is the low hormone phase. Most women will be able to hit PRs, perform high-intensity work, and experience peak motivation and immune function.
Luteal phase (week before menstruation): This phase is associated with higher cortisol levels. Women should eat more complex carbohydrates and protein to support their body’s tissue-building processes as your body prepares for fertilization and then shedding.
Tracking your cycle: Keeping a log of mental and physical states, cravings, and eating habits, sleep and moods can help you understand your body and prepare for the monthly changes. Knowing and understanding what & why things are happening to your body will further your health and wellbeing long term.
Pre-Workout Nutrition: What Women Should Eat Before Training
Proper pre-workout nutrition doesn’t require a massive meal—just enough fuel to support performance. Here’s a simple guide:
Before training: 15g of protein & 30g of carbs
An espresso shot with a scoop of protein powder & almond milk.
Two hard boiled eggs and a banana
Greek yogurt and some blueberries
Timing: Eat at least 30 minutes before training, then have a full meal within 45 minutes after the workout.
Without food before and after training, the first thing to be lost is lean muscle mass. This is especially critical during perimenopause when maintaining muscle mass is already more challenging.
Post-Workout Nutrition: Optimizing Recovery for Women
Women have a shorter post-workout recovery window than men, meaning they need to consume protein sooner to maximize muscle repair and growth.
Women (ages 20-40): 35g of protein within 45 minutes post-workout.
Perimenopausal and menopausal women: 40-60g of protein post-workout due to anabolic resistance (the body’s decreased ability to synthesize muscle from protein as it ages).
Recovery window: Women should eat protein within 1 hour, while men have up to 3 hours.
Key Takeaways
Fasted training is not an effective fat-burning strategy for women. Instead, it increases cortisol and reduces the ability to train at high intensities.
Women have more oxidative fibers, making them naturally more metabolically flexible. They don’t gain the same benefits from fasting as men do.
Skipping pre-workout fuel disrupts key hormones like estrogen, thyroid, and LH. This can lead to long-term hormonal imbalances.
Perimenopausal women need to prioritize strength training and proper fueling. Estrogen is essential for power and strength, and fasting limits performance potential.
Pre- and post-workout nutrition matters. Even a small amount of protein and carbs before a workout can make a significant difference in performance and recovery.
The bottom line? Women thrive when they fuel their bodies properly. Instead of chasing fat loss through fasted workouts, focus on eating strategically to support your energy, strength, and long-term health.
-Bailey Boettcher