What Does Stacy Sims Recommend for Hydration?

December 26, 2025 •

4 min read

While the standard 'eight glasses of water' advice persists, research by exercise physiologist Dr. Stacy Sims highlights that women's hydration needs differ significantly from men's, especially during intense training. Her evidence-based approach challenges common myths and provides actionable steps for optimizing fluid intake.

Quick Summary

Dr. Stacy Sims promotes a hydration strategy based on strategic sodium intake for preloading, low-carbohydrate electrolyte drinks during exercise, and gradual fluid replenishment post-workout.

Key Points

Pre-Hydrate with Sodium: Before a big event, hyperhydrate with sodium-rich fluids like broth or a weak electrolyte solution, especially during the high-hormone phase.
Separate Fuel from Fluid: Consume carbohydrates from food and use low-concentration electrolyte drinks (1.5-4% carb solution) for hydration to maximize absorption.
Sip, Don't Chug: Drink small, frequent sips throughout exercise rather than large gulps, as intense exercise can mute the thirst sensation.
Hydrate Slowly Post-Workout: After exercise, rehydrate gradually over several hours with an electrolyte solution to maximize fluid retention and prevent excessive urination.
Consider Female Physiology: Acknowledge hormonal effects on fluid retention and temperature regulation, especially during the luteal phase, and adjust electrolyte intake accordingly.
Use Urine Color as a Guide: Check the color of your first-morning urine to gauge your hydration status; pale yellow is optimal, dark yellow indicates dehydration.

The Fundamental Principles of Stacy Sims' Hydration

Dr. Sims’ hydration philosophy is rooted in acknowledging the unique physiological differences, particularly between sexes, and moving away from blanket recommendations. She emphasizes that proper hydration is not just about drinking plain water but ensuring optimal fluid balance through strategic electrolyte and carbohydrate intake. Her approach separates fueling (carbohydrate intake) from hydrating, addressing each need specifically to prevent gastrointestinal distress and maximize absorption. This individualized method considers factors like training intensity, environmental conditions, and hormonal fluctuations in women.

Separating Hydration from Fueling

Sims advocates for the 'food in the pocket, hydration in the bottle' strategy, meaning that caloric needs should be met with solid food, while fluids are used purely for hydration. When an athlete consumes a high-carbohydrate sports drink, the high concentration (osmolality) can slow gastric emptying. This can cause the body to pull water into the intestines to dilute the solution, leading to effective dehydration and GI issues like cramping or diarrhea. By keeping hydration drinks low in carbohydrates and rich in electrolytes, the body can absorb fluids more efficiently, ensuring adequate fluid balance without digestive upset.

Hydration Before Exercise: The Pre-Load Strategy

Starting a workout or race already dehydrated is a performance killer, and simply chugging plain water beforehand is not the solution. Sims recommends a specific pre-hydration protocol, especially for long events or exercising in the heat.

For endurance events or high-heat training: The night before, consume sodium-rich fluids like chicken broth or miso soup to 'hyperhydrate,' increasing your fluid volume before you start.
One hour before a regular workout: Drink 500 ml (about 2 cups) of a simple, homemade electrolyte solution.

This simple, low-carb solution consists of:

500 ml of water
1/16th tsp of salt
1 tsp of maple syrup (or another glucose/sucrose source)

This creates an approximately 1% carbohydrate concentration with adequate sodium, facilitating faster fluid absorption before exercise begins.

Hydration During Exercise: Sip Smart, Not Fast

During physical activity, the goal is to consistently replace lost fluids and electrolytes. Sims’ strategy focuses on controlled sipping rather than chugging large volumes, which can lead to bloating and inefficient absorption.

Frequent sipping: Set a timer to remind yourself to drink every 15-20 minutes, as your thirst sensation can diminish during prolonged effort.
Electrolyte drinks: Use a functional hydration drink, especially for sessions over 90 minutes or in hot, humid conditions. This drink should contain sodium, potassium, and magnesium, with a low carbohydrate concentration (1.5-4%).
Avoid high-carb drinks: High-concentration sports drinks can hinder absorption and cause GI distress. Sims' own low-carb formula, formerly Secret Drink Mix, exemplified this approach.

Hydration After Exercise: The Slow Rehydration Approach

Effective post-exercise hydration involves replenishing fluids gradually to maximize absorption and recovery. Guzzling water immediately after a workout can overwhelm the body's systems, leading to increased urination and minimal rehydration.

Immediate recovery: Consume a cold recovery drink within 30 minutes of finishing, containing carbohydrates and protein to help with muscle glycogen replenishment.
Sustained rehydration: Sip an electrolyte solution similar to your pre-workout drink over the next few hours to fully replenish fluid stores.
Check your urine: The color of your first-morning urine is a simple indicator. Pale yellow suggests good hydration, while dark yellow points to continued dehydration.

Comparison of Standard vs. Stacy Sims Hydration


Feature	Traditional Hydration Advice	Stacy Sims' Hydration Approach
Carbohydrates	Often high (6-8% solution) sports drinks for both fuel and fluid.	Low concentration (1.5-4%) electrolyte drinks for hydration only; fuel comes from food.
Sodium	May be overlooked or only present in standard sports drinks.	High sodium for pre-loading before big events; adequate sodium during exercise, especially for women.
Timing	'Drink when thirsty' or general fluid goals (e.g., 8 glasses).	Strategic, timed intake: pre-load, frequent sipping, slow post-exercise rehydration.
Absorption	Can be inefficient due to high carbohydrate concentration affecting gastric emptying.	Maximized with low-osmolality solutions to ensure rapid absorption and prevent GI issues.
Focus	General for all athletes; assumes men and women are the same.	Specific to sex physiology, acknowledging women's higher core temperature and different sweat composition.

The Critical Differences for Female Athletes

Sims' research highlights significant sex differences in hydration physiology, especially relating to the menstrual cycle. Women experience hormonal fluctuations that impact how they regulate temperature and retain fluid.

During the high-hormone (luteal) phase (days 15-28), rising progesterone increases core body temperature and delays the onset of sweating, making women more susceptible to dehydration. Sodium loss also tends to be higher in women, especially during this phase. For this reason, prioritizing electrolytes, particularly sodium, is crucial for female athletes to maintain fluid balance and optimal performance.

ROAR: How to Match Your Food and Fitness to Your Unique Female Physiology is Sims' book detailing her evidence-based approach for active women, covering hydration and other nutrition and training strategies.

Conclusion: A Nuanced and Personalized Approach

In conclusion, Stacy Sims’ recommendations for hydration move beyond generic advice to provide a strategic and personalized plan, especially vital for female athletes. By focusing on low-concentration electrolyte drinks, separating fluid intake from fueling, and implementing specific pre- and post-workout strategies, athletes can enhance fluid absorption, prevent GI distress, and support peak performance. Her work underscores the importance of listening to your body and adjusting your hydration based on factors like hormones, training intensity, and environmental conditions, leading to a more effective and scientific approach to staying hydrated.

Frequently Asked Questions

No, Dr. Sims debunks the myth that people need to drink a specific large volume of plain water daily. She emphasizes that other sources like watery fruits, vegetables, and tea contribute to overall hydration, and small, frequent sips are more effective than chugging large amounts.

Hyperhydrating is the process of deliberately increasing your fluid stores by consuming sodium-rich fluids like broth or specific electrolyte drinks. Dr. Sims recommends it the night before a big event to ensure you start with extra fluid volume, which helps maintain core temperature and performance, especially for endurance athletes.

Dr. Sims advises against high-carbohydrate sports drinks because their high concentration can slow gastric emptying and pull water into the intestines. This leads to effective dehydration and potential gastrointestinal distress like cramping or diarrhea during exercise.

For shorter workouts under 90 minutes, Dr. Sims suggests a simple homemade solution of water with a pinch of salt and a small amount of maple syrup, creating a low-carbohydrate electrolyte drink for effective absorption.

During the high-hormone (luteal) phase of the menstrual cycle, women experience a higher core body temperature and lose more sodium through sweat. Dr. Sims notes that this makes it even more critical to focus on electrolyte replenishment to prevent dehydration and support performance.

No, Dr. Sims' research indicates that coffee and tea do not significantly contribute to dehydration. She includes them in the overall fluid intake that helps maintain hydration throughout the day.

Drinking a large volume of fluid rapidly can cause a pressure response that signals the body to increase urination. Slowly sipping an electrolyte solution over several hours allows for better absorption and more complete rehydration, according to Sims.