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Nutrition Series, Part 2: Fluids

Explore the importance, and often overlooked benefits of proper hydration for your health and fitness goals.

For anyone fitness-minded, fueling yourself for performance goes hand in hand with strength training. But what about hydrating yourself? 

In this part of our nutrition series, we will explore the importance, and often overlooked benefits of proper hydration for your health and fitness goals.


Water is probably the “4th” macronutrient, if you will when it comes to necessary components of a healthy diet and fitness routine. However, water alone may not be the best choice for every athlete.

Hydration, fluids, water…it all basically means the same thing, right? Not quite. For athletes, both seasoned and just starting out, hydration is the unsung, or undervalued, hero of the nutrition and fitness world.

‘Hydration” or to “hydrate” is defined: to cause to absorb or combine with water or other fluids or to supply with ample fluid or moisture.[1]

For our purposes in this article, fluids are defined as liquids that contain various electrolytes or compounds that are useful for our metabolism. Water is the primary fluid in human metabolism and is absolutely essential for life.

Water (H2O) “is the largest single component of the body and is integral to cellular function and metabolism. It is a critical nutrient and losses can lead to severe disorders or death. Optimal health is dependent on the maintenance of adequate hydration, tissue perfusion, and electrolyte balance. Alterations in fluid balance can be affected by many factors such as insensible losses, disorders of digestion and absorption, and medical therapies.”[2]

Fun fact: about 60% of our body is water. Lean mass is made up of more water than fat mass, so an individual’s actual body water percentage can vary based on their body composition. Although there is no hard-and-fast rule on how much water each individual needs, there are calculations and “adequate intake” recommendations in the Dietary Reference Intakes for adults from ages 19yr and older. For women 2.7 Liters per day and for men 3.7 Liters per day is considered “adequate intake” to prevent acute effects of dehydration or metabolic abnormalities.2 Now, we know that people come in all sizes, heights, and activity levels, and daily fluid recommendations will vary for each individual’s needs. A calculation commonly used for estimating individual fluid needs is weight in kilograms(kg) x 25-35ml, however, this is only an estimate and does not take into account sweat losses during physical activity or the heat and humidity of the environment. Determining individual needs will take some trial and error, but thankfully we have several different methods for finding the right amount of hydration needed for different needs.

For example, a woman who is a 6 foot-tall beach-volleyball player weighing 165lbs (75kg) needs upwards of 2.6 Liters per day, whereas a man who is 5’6” and weighs 143lbs (65kg) working at a computer desk job needs about 2.2 Liters per day, according to our calculation of 35ml per kg of bodyweight. The athletes’ needs will clearly be higher given the nature of their daily physical activity and sweat losses vs someone with a mostly sedentary job. This example also illustrates how the “adequate intakes” are not accurate simply based on gender and age alone. The volleyball player will have high sweat losses during her matches, which must be replaced in addition to her regular fluid needs. A useful method to determine how much fluid is lost in sweat during a given activity is to measure start and end weight.


Water (H2O) is our typical go-to beverage for day-to-day and physical activity needs, and for good reason! Calorie and flavor-free, it is ideal for the majority of our fluid intake needs. However, as the saying goes you can have “too much of a good thing” and avoiding “overhydration” is as important as preventing “dehydration”. “Drinking excessive amounts of water can cause low sodium by overwhelming the kidneys' ability to excrete water. Because you lose sodium through sweat, drinking too much water during endurance activities, such as marathons and triathlons, can also dilute the sodium content of your blood.”[3] We call this condition hyponatremia, simply meaning “low blood sodium”. Symptoms of hyponatremia include nausea, vomiting, headache, confusion, fatigue, irritability, muscle weakness, and more seriously seizures or coma.3

Other signs that you are getting excessive amounts of water would include: very light-colored urine (extremely pale yellow or clear…), swelling in your fingers, toes, wrists, ankles, or abdomen, or shortness of breath while at rest or with minimal activity.

Intense physical activity with an inappropriate hydration strategy can result in hyponatremia as well. However, that is why pre-and post-workout body weights are logged, and sports drinks or water with electrolytes added are encouraged during training and sporting events. Drinking water is always encouraged, however, plan to space out your intake during the day and when “nature calls”, answer!

So, before I scare you into throwing out your Britta Filter, let me say that this condition is avoidable and reversible if addressed quickly. Firstly, have electrolyte-containing beverages as part of your hydration strategy. Whether it is a ready-to-go sports drink, a powdered mix, or milk (or a non-dairy milk alternative) find what works for your taste and you will be more likely to stay consistent in your strategy. Second, weigh yourself before and after strenuous exercise and replace the difference, not in excess. If you do start to experience weakness, confusion, fatigue, etc. and you have been drinking plain water consistently, seek medical attention asap. NOTE: If you are working with your coach on sport-specific hydration requirements, discuss the rationale behind the strategy and keep them informed if you begin to “feel off” while following the hydration protocol.


Now that we have explored one extreme, we should touch on the other. Dehydration is simply not having enough water in your body for normal functions. Thirst is probably the first thing to come into your mind when you hear “dehydration”. We have all heard or said, “wow, I’m thirsty, I must be dehydrated”. While thirst is our body telling us it’s time to drink up, it is not always a reliable early warning sign. We can easily override our thirst sensation, especially if we are busy and distracted, or intentionally (remember that long trip and the airplane bathroom you don’t want to use?). Dark-colored urine, dizziness, fatigue, confusion, and extreme thirst3 are the most common signs and symptoms of dehydration in adults. Mild dehydration is something we can all experience from time to time, (i.e a long trip without hydrating, a hangover, after an intense workout without drinking, a session in the sauna, etc.) and is usually quickly corrected when we start drinking the usual beverage intakes again. However, quite a few people find water “boring” or “tasteless” and opt for sugar-sweetened beverages instead. Instead of reaching for a soda or sweet tea, try these water-dense foods. Certain foods have higher water content than others and would be good choices to add to your diet especially in hot conditions or to supplement water intakes in addition to your typical beverage intakes. This is not an exhaustive list, however, it may spark some inspiration for you to look for high-water foods if drinking glass after glass of H2O is a little “too much to swallow.” Overall, staying appropriately hydrated will help you reach your health and fitness goals and should be a priority, not an after-thought. Coming up next, we will touch on the ever-popular topic of supplements!

Overall, staying appropriately hydrated will help you reach your health and fitness goals and should be a priority, not an after-thought. Coming up next, we will touch on the ever-popular topic of supplements!

Jess G

About the author Jessie Gall, MS, RD, LD

Jess is a Metro-Atlanta-based dietitian in the state of Georgia with 8 years experience as a Registered Dietitian in the hospital setting, as well as corporate wellness events, and individual counseling. She received her Bachelor of Science and Master of Science from Georgia State University and is a Licensed and Registered Dietitian Nutritionist.

Jess enjoys helping her patients have the “lightbulb moments” in their nutrition care and recommendations. Her “food philosophy” is that food is functional and fun! Eating for health does not have to be boring or tasteless. All things in moderation make for a more enjoyable, and healthy relationship with food. There is no one-size-fits-all approach to nutrition, but there are research-based recommendations, and she enjoys helping each patient/client find what works for their lifestyle, goals, and needs. Jess is also an NPC Bikini division competitor, NASM Certified Nutrition Coach, and mother of twin boys.

Instagram @Jess_G_Fit


[1] Webster’s Dictionary

[2] Nutrition Care manual

[3] Mayoclinic.org

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