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The adult human body averages ~53% water. [7] This varies substantially by age, sex, and adiposity. In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ±6% for females and 58 ±8% water for males. [8]
The figure for water fraction by weight in this sample was found to be 58 ±8% water for males and 48 ±6% for females. [4] The body water constitutes as much as 75% of the body weight of a newborn infant, whereas some obese people are as little as 45% water by weight. [5] This is due to how fat tissue does not retain water as well as lean tissue.
In lean healthy adult men, the total body water is about 60% (60–67%) of the total body weight; it is usually slightly lower in women (52–55%). [2] [3] The exact percentage of fluid relative to body weight is inversely proportional to the percentage of body fat. A lean 70 kg (150 lb) man, for example, has about 42 (42–47) liters of water ...
Claude Bernard, French physician who introduced the concept of homeostasis. The human body and even its individual body fluids may be conceptually divided into various fluid compartments, which, although not literally anatomic compartments, do represent a real division in terms of how portions of the body's water, solutes, and suspended elements are segregated.
Total body water in healthy adults is about 50–60% (range 45 to 75%) of total body weight; [1] women and the obese typically have a lower percentage than lean men. [2] Extracellular fluid makes up about one-third of body fluid, the remaining two-thirds is intracellular fluid within cells. [3]
A wide variety of body composition measurement methods exist. The gold standard measurement technique for the 4-compartment model consists of a weight measurement, body density measurement using hydrostatic weighing or air displacement plethysmography, total body water calculation using isotope dilution analysis, and mineral content measurement by dual-energy X-ray absorptiometry (DEXA). [1]
In chemistry, the mass fraction of a substance within a mixture is the ratio (alternatively denoted ) of the mass of that substance to the total mass of the mixture. [1] Expressed as a formula, the mass fraction is:
The recommended daily amount of drinking water for humans varies. [1] It depends on activity, age, health, and environment.In the United States, the Adequate Intake for total water, based on median intakes, is 4.0 litres (141 imp fl oz; 135 US fl oz) per day for males older than 18, and 3.0 litres (106 imp fl oz; 101 US fl oz) per day for females over 18; it assumes about 80% from drink and 20 ...