Which percentage of body weight is total body water (TBW) for a normal adult male?
40%
60%
80%
100%
The correct answer and explanation is:
Correct Answer: 60%
Explanation (300 Words):
Total Body Water (TBW) refers to the amount of water contained in a person’s body, and it is a crucial component for maintaining physiological balance. For a normal adult male, TBW typically constitutes approximately 60% of body weight. This means that if a man weighs 70 kilograms, around 42 kilograms (or liters) of that weight is water.
This water is distributed across different compartments in the body:
- Intracellular fluid (ICF): About two-thirds (~40% of body weight) of TBW is found inside the cells.
- Extracellular fluid (ECF): The remaining one-third (~20% of body weight) is outside the cells, including plasma, interstitial fluid, and transcellular fluid.
The 60% figure can vary depending on several factors:
- Age: TBW percentage decreases with age as fat content increases and muscle mass (which holds more water) decreases.
- Gender: Women generally have a lower TBW percentage (about 50%) compared to men due to a higher proportion of body fat.
- Body composition: Muscle tissue holds more water than fat, so lean individuals tend to have a higher TBW percentage.
Water in the body plays several vital roles:
- It is essential for cellular function, including nutrient transport and waste removal.
- It acts as a solvent for biochemical reactions.
- It helps regulate body temperature and maintain blood pressure.
A deviation from the normal TBW—such as dehydration or fluid overload—can lead to significant health issues like electrolyte imbalance, hypotension, or edema.
In conclusion, 60% is the accepted standard for TBW in a healthy adult male, highlighting water’s fundamental role in maintaining normal physiological function.