Body water percentage
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Body Water Percentage in Adults: Key Values and Influencing Factors
In healthy adults, total body water (TBW) typically makes up about 60% of body weight in males and 50–55% in females, with some sources reporting a range of 55–60% for males and 50–55% for females, depending on age, sex, and body composition 1278. This percentage can vary due to factors such as age, sex, and the amount of body fat present 2410.
Age-Related Changes in Body Water Percentage
Infancy and Childhood
Newborns and infants have the highest body water percentage, with term-born newborns averaging about 74% and preterm infants reaching up to 90% at 26 weeks gestation, gradually decreasing as they approach term 35. During the first six months of life, this percentage drops, and from 6 months to 11 years, it stabilizes between 53% and 63% regardless of sex .
Adolescence to Adulthood
In normal-weight children aged 3–10 years, TBW% is similar for both sexes at around 62%. For males, this percentage remains stable into adulthood, while for females, it decreases during puberty to about 55% and remains relatively unchanged until later adulthood .
Older Adults
After age 60, TBW% decreases in both sexes, dropping to about 57% in males and 50% in females . This decline is mainly due to an increase in body fat and a decrease in lean body mass as people age 210.
Impact of Body Composition on Body Water Percentage
Body fat contains much less water (about 10%) compared to lean tissue, so individuals with higher body fat percentages have lower TBW% . Overweight and obese individuals, regardless of sex, have significantly lower TBW% compared to those with normal weight 24. There is a strong negative correlation between body fat percentage and total body water: as body fat increases, TBW% decreases 410.
Distribution of Body Water: Intracellular and Extracellular Compartments
Of the total body water, about two-thirds is found inside cells (intracellular), and one-third is outside cells (extracellular). The extracellular compartment is further divided into intravascular (within blood vessels) and interstitial (between cells) spaces . This distribution is important for maintaining fluid balance and supporting physiological functions 19.
Stability and Variability in Adulthood
Longitudinal studies show that, after adjusting for changes in body fat and fat-free mass, TBW volume remains relatively stable through most of adulthood, especially in men. In women, there is a slight decline with age, but this is largely explained by changes in body composition rather than age alone .
Conclusion
Body water percentage is highest at birth and gradually decreases with age, stabilizing in childhood and adolescence, and declining again in older adulthood. Males generally have a higher TBW% than females, and individuals with more body fat have a lower TBW%. The distribution of water between intracellular and extracellular compartments is consistent across healthy adults, but overall TBW% is influenced by age, sex, and body composition 12345789+1 MORE.
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