Why Women Shouldn't Intermittent Fast—and Should Always Train Fed
If you’ve ever thought about intermittent fasting (IF) as a shortcut to weight loss or better energy, you’re not alone. Social media is packed with “fasted cardio” success stories and 16:8 fasting schedules promising rapid results. But here's the catch: most of those stories are based on research done on men—not women.
And when it comes to female physiology, especially in the postpartum years or while training, fasting can do more harm than good.
Here’s why women—especially active mums—should skip the fasting trend and focus on training in a fed state, according to the science of female-specific health expert Dr. Stacy Sims.
1. Most Fasting Studies Are Done on Men
Dr. Stacy Sims is famous for saying, “Women are not small men.” And it’s more than a catchy phrase—it’s science. The majority of fasting studies are conducted on male participants. Women have different hormonal profiles that affect how we respond to stress, food, and exercise. Women’s endocrine systems are far more sensitive to calorie restriction. When we fast, our bodies don’t just use up fat for fuel—instead, our stress hormone (cortisol) rises, and our body begins to hold onto fat, thinking we’re in a famine.
2. Fasting Triggers Hormonal Chaos
Even short-term fasting can lead to:
Disrupted menstrual cycles
Increased cortisol (hello, anxiety and poor sleep)
Slowed metabolism
Decreased thyroid function
Especially in the postpartum or perimenopausal window, this hormonal shift can amplify fatigue, mood swings, and stubborn fat storage—the exact opposite of what most women are trying to achieve with IF.
As Sims points out: “Women’s bodies are designed to survive first, reproduce second, and perform third. When we fast, we turn on the survival signal.”
3. Training Fasted = Stressing the Body (Not Building It)
If you're getting up early to train and skipping breakfast, it might feel “disciplined”—but it’s working against you.
When you train without food, your cortisol is already high, and fasted training spikes it even more. Instead of burning fat, you can trigger muscle breakdown, poor recovery, and increased fat storage—especially in the belly.
Women perform better and recover faster when they train fed.
What to do instead?
Eat something with carbs and protein before training—even if it’s small. A banana with nut butter, a slice of toast with egg, or a half protein bar is enough to blunt the cortisol spike and fuel your muscles.
4. Underfueling = Overtraining Symptoms
Many active mums are unintentionally underfuelling by skipping breakfast or delaying meals (even if they’re not “officially” fasting). This creates a low energy availability (LEA) state.
According to Sims, LEA is one of the most common—and overlooked—causes of fatigue, weight retention, and irregular cycles in active women.
Symptoms of underfueling include:
Poor recovery
Irritability or anxiety
Plateaus in performance or weight loss
Disrupted sleep
Sound familiar?
5. Fuelling = Performance + Health + Results
When you eat enough—and at the right times—you don’t just feel better, you perform better. You recover faster, lift heavier, run longer, and most importantly—support your long-term hormonal health.
Instead of focusing on fasting windows, focus on fueling windows:
Eat protein within 30–60 minutes of waking
Fuel before training
Prioritize post-training recovery meals
Eat consistently throughout the day
Final Word: You Don’t Need to Earn Your Food
Food is not something to restrict, delay, or fear—it’s your tool to come back stronger.
Intermittent fasting might be trendy, but it’s not designed for the female body—especially not for women juggling recovery, training, motherhood, and hormonal shifts.
Instead of fighting your physiology, work with it.
Train fed. Fuel fully. And reclaim your energy, strength, and identity.
Want help making this happen in real life?
Explore my Fuel Your Comeback program and personalised nutrition coaching designed for active mums who want real, lasting results—without restriction.
