Body Weight, Human

together with other anthropometric features (height and chest circumference), an important index of physical development and state of health.

Human body weight is a function of sex, height, nutrition, heredity, socioeconomic conditions, and geographic area. The average weight of newborn Europoid boys is 3,400-3,500 g, and that of newborn Europoid girls, 3,200-3,300 g. During the first year of life children gain an average of 6-7 kg, and, by the end of the second year, another 2-3 kg. The average body weight of boys is usually somewhat greater than that of girls of the same age, except during puberty (age 12-13 in Europoid girls), when the weight of girls exceeds that of boys by 3-4 kg. At age 15, male weight begins substantially to exceed female weight. The period from age 25 to 45 is characterized by relatively stable weight. Body weight falls considerably in old age, mainly because of loss of water. The average weight of adult Europoid males is 65-68 kg. Women weigh 8-10 kg less. The lowest average body weight is found among the pygmies of Africa and Asia. As a rule, the body weight of the peoples of tropical regions is less than that of the peoples of temperate regions.

Human body weight fluctuates daily by ±2 kg. Body weight may be subdivided into fatty (passive) weight and defatted (active) weight. The ratio between these may vary. In athletes, for example, defatted weight is relatively more developed than fatty weight. Some specialists suggest differentiating cellular from noncellular body weight, because there is an exchange of matter and energy in the former, but only maintenance and transport functions occur in the latter. It is believed that fat accounts for the major part of weight gains and losses (an average of more than 600 g of fat for every kg gained or lost). As a result of acceleration, increases in human body weight have been noted almost universally. Indexes of human body weight are often used in constructing various indexes and diagrams in the diagnosis of human physical development.