Dr. Stacy Sims, an exercise physiologist and nutrition scientist, is a prominent advocate for female-specific training and nutrition, championing the mantra 'Women are not small men'. Her research highlights how female athletes respond differently to training and nutrition compared to men, largely due to hormonal differences. This is particularly important when considering pre-workout fueling, as improper timing and content can hinder performance, recovery, and overall hormonal health.
The Critical Case Against Fasted Training
Sims emphasizes that active women, especially those training in the morning, should avoid exercising on an empty stomach. When you wake, the stress hormone cortisol is naturally high. Exercising while fasted exacerbates this, keeping the body in a state of stress. This elevated sympathetic drive (fight-or-flight response) can negatively affect muscle protein synthesis, disrupt hormone function (including thyroid), and lead to increased fatigue and fat storage over time. A small, strategically timed meal or snack can signal to the brain that adequate energy is available, preventing the body from entering a catabolic state and blunting the cortisol spike.
Fueling Differences Based on Workout Type
Sims' recommendations for pre-workout fuel are not one-size-fits-all. They are specifically tailored to the type of exercise you are doing. The key is to provide just enough fuel to get amino acids circulating and stabilize blood sugar without a heavy, full feeling.
- For Strength Training: The focus is on getting about 15 grams of protein into your system. This provides the necessary amino acids to kickstart muscle protein synthesis and recovery even before you begin. A protein shake, a scoop of protein powder with fortified coffee, or Greek yogurt are excellent options.
- For Cardiovascular Training (up to 60 minutes): A combination of protein and carbohydrates is recommended. Aim for around 15 grams of protein and 30 grams of carbohydrates. The carbohydrates provide an energy source to fuel the workout, helping maintain intensity. A total of fewer than 200 calories is often sufficient.
- For Longer Endurance Events (90+ minutes): For prolonged exercise, a more substantial carbohydrate-focused meal is needed 90 minutes or more in advance to top off glycogen stores.
Sample Pre-Workout Fueling Options
Here are some practical pre-workout snack examples based on Dr. Sims' advice:
- Half a banana with a tablespoon of almond butter.
- A small pot of Greek yogurt with a handful of berries.
- A rice cake with almond butter and a drizzle of honey.
- Protein-fortified cold brew coffee with a small amount of sweetened oat milk.
- One or two hard-boiled eggs with a handful of almonds.
- A small smoothie with fruit and protein powder.
The Impact of the Menstrual Cycle on Pre-Workout Nutrition
Understanding how your hormones fluctuate during the menstrual cycle is key to optimizing your fueling strategy. The needs of your body can change based on the cycle phase, particularly during the high-hormone (luteal) phase following ovulation.
- Follicular Phase (Low Hormone): Your body is more resilient and handles carbohydrates more efficiently. This is a great time for high-intensity work, and fueling with carbs around workouts is highly effective.
- Luteal Phase (High Hormone): Rising estrogen and progesterone increase core temperature and fluid loss, while also increasing fat utilization for fuel. During this phase, you may need a slight increase in carbohydrate intake pre-workout to maintain energy levels. Increased hydration with electrolytes is also crucial. Your thirst signals may be dulled, so you cannot rely on thirst alone.
Pre-Workout Nutrition Comparison
| Feature | Strength Training (before) | Cardio/Endurance (before) |
|---|---|---|
| Primary Goal | Initiate muscle protein synthesis | Sustain energy and intensity |
| Protein | ~15 grams | ~15 grams |
| Carbohydrates | Not the primary focus | ~30 grams |
| Meal Timing | 30-60 minutes before workout | 30-60 minutes before workout (shorter workouts) |
| Key Effect | Blunts cortisol, signals incoming nutrition | Provides fuel for intensity, stabilizes blood sugar |
| Example Snack | Greek yogurt with seeds | Banana with nut butter |
Conclusion
For optimal performance, recovery, and overall health, Dr. Sims' philosophy is clear: women must fuel intentionally before exercise. This approach works with female physiology rather than against it by blunting the stress response and providing the brain and muscles with necessary nutrients. By adjusting your protein and carbohydrate intake based on your workout type and cycle phase, you can ensure your body is ready to perform and adapt effectively. For more resources, visit the official Dr Stacy Sims website.
The Role of Hydration and Electrolytes
Dr. Sims' pre-workout advice is not just about food; proper hydration is paramount, especially for women. Women tend to lose more sodium during exercise compared to men, and fluid needs can change throughout the menstrual cycle. Adding electrolytes to your water, or choosing a lower-carb, higher-electrolyte drink, can help manage fluid balance. This is especially important during the luteal phase when hormone levels can affect hydration status.
Listen to Your Body
While these guidelines provide a strong framework, Sims also stresses the importance of listening to your body. Factors like sleep, stress levels, and individual menstrual cycle patterns should all be considered. If you feel low on energy, a small pre-workout snack can make a significant difference. The ultimate goal is to work with your body, not push it into a state of burnout.
