When it comes to your health, most of the focus is on your levels of body fat and muscle mass, which is important. But not to be overlooked is your body water. 

Body water, and not your muscle or fat, makes up the largest percentage of body weight. Let’s explore the significance of body water and what a healthy body water percentage means for your overall health.

What is Body Water?

Body water is the amount of water content found in the human body. Up to 60% of the human body contains water. Knowing what percentage of the human body is water helps you understand how crucial hydration is for our overall health.

Nearly all of your body’s major systems depend on water to function properly. Water helps:

• regulate internal body temperature

• carry oxygen and nutrients

• lubricate joints

• flush out waste products

• dissolve minerals and nutrients

• protect organs and tissues

Your body experiences a certain amount of fluid loss each day through perspiration, urine, and bowel movements. The daily recommended water intake is about 3.7 liters of fluids/day for men and 2.7 liters of fluids/day for women. Of course, this number will change depending on your activity level, diet, age, and body weight.

Maintaining a healthy body water percentage is key to supporting body functions and ensuring your body operates at its best.

How Body Water Affects Overall Health

Body water plays a crucial role in nearly every aspect of your physical and mental well-being. Maintaining proper hydration is key to keeping your body functioning optimally. Here’s how it impacts various areas of health:

• Energy Levels: When you’re adequately hydrated, your body can efficiently transport nutrients and oxygen to your cells, helping you maintain high energy levels throughout the day. Even mild dehydration can lead to fatigue, reducing your overall energy and making daily tasks feel more draining.

• Digestion: Water is essential for digestion and nutrient absorption. It helps break down food and moves it through the digestive system, preventing constipation. Additionally, proper hydration supports the production of saliva and gastric juices that aid in the breakdown of food.

• Skin Health: Your skin is one of the first places to show signs of dehydration. When your body lacks water, it can become dry, flaky, and less elastic. Hydration helps maintain skin moisture, improving its appearance and preventing wrinkles and fine lines. Proper water intake also helps flush toxins from the body, promoting a clearer complexion.

• Cognitive Function: Hydration is critical for brain function. Dehydration can impair concentration, memory, and mood. Studies have shown that even mild dehydration can affect cognitive performance, making it harder to focus and think clearly. Drinking enoug

What Should Your Body Water Percentage Be?

The healthy body water percentage range is influenced by your age, sex, and fitness level.

When we are born, we are almost 80% water. By the time we reach our first birthday, that number drops to about 65%.

Adult women naturally have more body fat than adult men so they will carry less body water because fat tissue contains less water than lean body mass. The following body water percentage charts outline average body water percentages across various age groups for both males and females:​

Body Water Percentage by Age and Sex

Body composition, particularly the ratio of lean body mass to fat mass, significantly impacts body water percentage.

Individuals with higher lean body mass, such as athletes or those with higher muscle mass, typically have a higher body water percentage. Conversely, individuals with higher fat mass tend to have a lower body water percentage.​

Body Water Percentage by Fitness Level

Which Organs in the Human Body Have More Water?

Almost every cell in your body contains water: body water makes up 79% of your muscles, 73% of your brain, and even 31% of your bones. 

Overall your total body weight can be 45-65% water.

• Brain and heart – 73%

• Lungs – 83%

• Skin – 64%

• Muscles and kidneys – 79%

What is Extracellular Water and Intracellular Water

A better gauge of healthy body water levels is your ratio of extracellular fluid (ECW) to your total body water (TBW). To understand what that means, we must first define your extracellular water and intracellular water. 

As discussed above, your body water is present not only in your blood, but in your muscle tissue, body fat, organs, and inside every cell in your body. To account for all this, your total body water (TBW) can be divided into two basic groups:

Extracellular Water (ECW)

Extracellular water is the water located outside your cells. The water in your blood falls into this category. Roughly 1/3 of your fluid is attributed to ECW, and this water is found in your interstitial fluid, transcellular fluid, and blood plasma.

Extracellular water is important because it helps control the movement of electrolytes, allows oxygen delivery to the cells, and clears waste from metabolic processes.

Intracellular Water (ICW)

Intracellular water is the water located inside your cells. It comprises 70% of the cytosol, which is a mix of water and other dissolved elements. In healthy people, it makes up the other two-thirds of the water inside your body.

The intracellular water is the location of important cellular processes, and although it has many functions, a very important one is that it allows molecules to be transported to the different organelles inside the cell. Essentially, the Intracellular water picks up where the Extracellular water left off by continuing the pathway for fuel to be transported to the cells.

What is a Healthy Water Balance?

When it comes to your body water and overall health, the most important thing to strive for is balance. Your Intracellular fluid and Extracellular fluid must remain at the same levels with respect to each other.

A healthy distribution has been estimated at a 3:2 ratio of ICW: ECW. If your body water falls out of balance, this can signal changes in your health and body composition. Whether these changes are positive or negative depends on which type of water becomes unbalanced.

What does increased intracellular water (ICW) mean?

Having slightly more ICW than normal isn’t necessarily a bad thing. In fact, it can signal positive changes in your body composition. 

When you gain muscle mass, the number and size of your muscle cells increase. As muscle cells expand, they need more ICW to perform their functions. Research shows that resistance exercise can lead to increased ICW, which is a sign of increased lean body mass. This is a good thing for your health, with several benefits:

• Increased Energy Use: Basal Metabolic Rate (BMR) is the number of calories the human body burns at rest. It is the baseline for the calories the human body needs every day to operate and maintain daily functions. With increased Lean Body Mass, your energy needs will increase as a result of a higher BMR. If you don’t increase your daily calorie intake, but increase your Lean Body Mass/BMR, you will create a calorie deficit – which can lead to fat loss.

• Increased Strength: Your Lean Body Mass is sometimes described as your fat-free mass. Your Lean Body Mass accounts for all your weight due to water, muscle mass, bone, and protein. One of the easiest ways to influence the amount of Lean Body Mass you have is to increase your muscle mass. Generally, increased muscle mass leads to increased strength.

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• Increased Immune System: Increased Lean Body Mass through exercise has been associated with increased immune system functionality. This will help your body fight off illnesses more easily.

What does excess extracellular water mean (ECW)?

If your ECW increases in relation to your ICW, this is something you should take special note of. Unlike ICW, you do not want to see your ECW increasing beyond normal levels. Excess ECW can indicate health risks, including:

Inflammation: During inflammation, the body sends additional blood flow to the damaged area. This causes an increase in extracellular water in a particular area. Inflammation occurs when part of the body gets damaged or bruised and is a normal bodily response to injury. This is called acute inflammation and is a temporary increase in ECW. Chronic inflammation, however, is something more serious that isn’t always readily detected. It is marked by long-term swelling/ECW increases caused by cellular stress and dysfunction. Chronic inflammation can lead to serious diseases if allowed to persist over time, including renal failure, cancer, and heart disease. including renal failure, cancer, and heart disease.

• Renal Disease (Kidney Failure): One of the kidneys’ major functions is to filter your blood and remove toxins produced in the body. One important substance that the kidneys filter out is sodium, an element that is found in salt. When your diet includes more sodium than your kidneys can filter out, which occurs in people who have failing kidneys, your extracellular water levels will increase. In some cases, this increased extracellular water shows visible swelling throughout the body and is a condition known as edema. Edema can cause additional strain on the body by contributing to weight gain, blood pressure, and other complications.

• Unhealthy Fat Mass Levels (Obesity): Obese individuals are characterized by having too much body fat, which among other things, leads to body water disruption due to excess ECW. This is because excess visceral fat can trigger production hormones that can lead to the disruption of a bodily system called RAAS. This excess ECW causes stress in the body due to its effects on the internal organs, which can exacerbate obesity and cause a dangerous cyclic effect.

How to Find Your Total Body Water?

Since it’s so important to keep an eye on your water balance, you’ll need to know how to calculate total body water. There are two major methods to measure and determine your body water levels. These are the dilution method and the BIA method.

The dilution method

The dilution method involves drinking a known dose of heavy water (deuterium oxide) and allowing it to distribute around the body. Once the water has had time to settle, the amount of heavy water is compared with the amount of normal water. The proportion will reflect the amount of total body water. To determine ECW, sodium bromide is used instead of heavy water.

The dilution method is recognized as a gold standard for measuring total body water; however, these tests would need to be done at a hospital under the guidance of a trained physician. This test takes several hours to complete during which any fluid of any type going in or out of the body has to be carefully recorded.

For these reasons, you’re unlikely to have this test performed unless your doctor needs to know your total body water with absolute certainty because of a serious health complication.

Bioelectrical impedance analysis (BIA)

The second, more accessible method to determine body water content is bioelectrical impedance analysis (BIA). For most people who do not have serious medical issues, this method is much more practical than the dilution method.

A small electrical current is applied to the body and the opposition that the current experiences (impedance), is measured. From that impedance result, a BIA device can report your body water percentage. Advanced BIA devices are able to reflect the difference in Intracellular and Extracellular water as well, which can reveal the ICW: ECW balance.

Watson Formula

If you prefer a DIY approach, you can estimate your water percentage in the body using a simple formula based on your weight and gender. Here’s a Watson formula:

• For males: TBW (liters)=2.447−(0.09516×age)+(0.1074×height in cm)+(0.3362×weight in kg)

• For females: TBW (liters)=−2.097+(0.1069×height in cm)+(0.2466×weight in kg)

This formula gives an estimate of body water percentage, but keep in mind that it may not be as precise as the more advanced methods (such as BIA or dilution testing). It provides a good starting point for those who want a rough idea of their hydration levels.

Signs of Dehydration

Dehydration occurs when your body loses more water than it takes in, leading to an imbalance in body water levels. It’s important to recognize the signs of dehydration early so you can take action to restore hydration before it leads to more serious health issues. Common signs of dehydration include:

• Thirst: The most basic sign of dehydration is feeling thirsty. Your body signals that it needs more water to maintain balance. If you’re feeling thirsty, it’s important to drink water immediately to rehydrate.

• Dark Yellow Urine: One of the clearest indicators of dehydration is dark yellow or amber-colored urine. When you’re properly hydrated, urine should be light yellow or clear. Dark urine suggests that your body is conserving water and not flushing out enough waste.

• Dry Mouth and Skin: Dehydration can cause your mouth and skin to feel dry. Without adequate moisture, your skin can become less elastic and show signs of dryness. Similarly, you might experience a dry or sticky feeling in your mouth, indicating that your body needs water.

• Fatigue and Dizziness: When you’re dehydrated, your body has to work harder to function, which can lead to feelings of fatigue and dizziness. Dehydration affects blood circulation and the delivery of oxygen and nutrients to your cells, leading to low energy and lightheadedness.

• Headaches: Dehydration can trigger headaches due to reduced fluid levels in the brain and changes in blood pressure. If you’re experiencing frequent headaches, it may be a sign that you need to drink more water.

• Confusion or Irritability: As dehydration progresses, it can affect your cognitive function and mood. Irritability, confusion, or difficulty concentrating are common signs of more severe dehydration, which requires immediate attention.

How to Increase Body Water Percentage

Maintaining a balanced ratio of approximately 3:2 is ideal for optimal health. If you find that this ratio is beginning to fall out of balance, there are some things you can do. Fortunately, these tips aren’t anything you already haven’t heard before: maintaining a healthy diet, staying hydrated by drinking enough water, and exercising regularly:

1. Reduce Excess ECW: To avoid excess extracellular water, consider reducing sodium (salt) intake. Excess sodium is primarily located in your ECW. When too much sodium enters the body, it causes the body to draw water out of your cells, which reduces intracellular water (ICW). Reducing sodium intake helps lower ECW and has several other health benefits, making it a great practice for optimal health.

2. Increase ICW Through Exercise: Increasing your intracellular water (ICW) can be achieved by:

• Building Lean Body Mass: Regular exercise, particularly strength training, increases muscle mass. As muscle cells grow, they require more ICW to function properly.

  • Combating Obesity: Exercise also helps reduce fat mass, which in turn reduces ECW associated with obesity over time. By lowering excess fat, your ICW: ECW balance improves naturally.

3. Adopt Healthy Habits: To achieve and maintain a better ICW: ECW ratio, focus on:

• Regular Exercise

  • A Balanced Diet

  • Adequate Hydration