Explain Water - An Essential but Overlooked Nutrient?

You may already know that the total body water (TBW) constitutes 50-60% of the body weight. A 70 kg 'standard male' contains 42 litre water - 60% of his body weight while an adult female contains 55% of body weight as water. Why is there a difference in TBW content between males and females? This decrease is due to a higher fat content found in females. The portion of water in the body, however, varies in individuals depending on body composition. Let us see how. For example, you will find that muscular people have a higher proportion of water than the less muscular or obese people.

Table:  Percentage of TBW in infants, children and adult

Can you say why? Well, simply because the striated muscle contains more water than any other body tissue (except blood). While water content of the muscles is 65-75%, it amounts to less than 25% of the weight of fat. Consequently, the differences in body water between individuals are largely due to the variations in body composition i.e. differences in lean tissues vs. fat. Similarly, males have a higher proportion of water in their bodies than do females because they have a higher proportion of lean tissue and a lower proportion of fat. An athlete will have a greater proportion of body water than a non-athlete as he/she has developed a relatively larger proportion of lean body mass. You would notice that there is a steady fall in the proportion of water as we age, which is due to an increased deposition of fat in the body, as well as, loss of muscle mass with age. Table presents the percentage of total body water at different stages of lifecycle.