Health Glossary

Water Retention Rate (ECW/TBW)

The water retention rate shows the relationship between extracellular water as a proportion of total body water and is a general indicator of body water balance, hydration status and in turn, overall health.
Author Dr. Jacky Lio
Date 2021-07-16
Updated on 2021-07-21
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What is extracellular water (ECW) and intra cellular water (ICW)?What is the normal range of water retention rate?Why would your ECW be high?What happens when ECW increases?How do I maintain the ECW/TBW ratio?

What is extracellular water (ECW) and intra cellular water (ICW)?

Extra Cellular Water (ECW) is the water located outside your cells. Extracellular water is important because it helps control the movement of electrolytes, allows oxygen delivery to the cells, and clears waste from metabolic processes from cells. 

Intra Cellular Water (ICW) is the fluid located inside your cells. The intracellular water is very important as it allows molecules to be transported within the cells. 

What is the normal range of water retention rate?

In a healthy state, your ECW/TBW ratio should fall within the range 0.360 to 0.390.  A value closer to 0.360 (or below) is commonly observed in athletes and reflects more Intracellular Water, Lean Body Mass, and strong cellular nutrient retention. 

Conversely, a value nearing 0.390 is indicative of greater Extracellular Water, Body Fat Mass, inflammation/water retention, and dehydration. If your ECW/TBW ratio exceeds 0.400, it is recommended that you consult your physician.

Why would your ECW be high?

It can be an early sign of an imbalance in your body. Such imbalances may be in hormone, protein, sodium, potassium, magnesium or pH levels. As a result of these imbalances, one can develop hypertension, decreased mental alertness, nausea, dizziness, headaches, fatigue and shortness of breath. An increase in ECW will generally occur as ICW increases, however an increase in ECW without a respective increase in ICW could indicate the presence of an injury or disease state.

What happens when ECW increases?

An increase in body fat is accompanied by an increase in extracellular water as well. In other words, body fat lacks adequate amounts of intracellular water. An increase in extracellular water (or the water outside your cells) can cause excess weight and swelling in your limbs.

How do I maintain the ECW/TBW ratio?

Reducing the amount of sodium (salt) in your diet reduces excess ECW. ECW increase caused due to obesity can be combated with regular exercise and physical activity. Increasing your Lean Body Mass/increasing muscle mass through exercising can also help to increase ICW, inturn, reducing the ECW.

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