Body weight is a biometric feature and denotes the physical mass of a human (or animal), usually expressed in kg. It is shortly after the birth of the smallest and then takes to adulthood in normal development, together with the height increasing.

Many people, especially in developing countries suffer from underweight because they have too little to eat. Overweight (or its more severe form obesity) is a common problem that has increased in developing countries.

Also, eating disorders can cause underweight (eg anorexia and bulimia) or lead to obesity (key to youth body advice). The birth weight of the newborn is determined in many countries, recorded and analyzed statistically.

There is a correlation between (over) weight of women in labor and (over) weight of the newborn. obesity in the womb which makes the birth more risky (from 4000 grams take birth risks a little, from 4500 grams clearly) and can be lifelong problems have the result for infants. Obese women are more likely to suffer gestational diabetes. Then her blood contains too much sugar.

The continuing flood of sugar also damages a mechanism, called fetal programming. The control of food intake in the brain is disturbed in this case, the children are not tired. Body weight can be measured quickly and easily using a scale. A quantitative assessment of body weight in relation to body size is considered problematic. A number of indices have been developed to in the last 150 years.

In the second half of the 20th Century was often assumed by an ideal weight of only 90 % for men and only 80 % for women of the value calculated above, but more for aesthetic than for medical reasons.

The Broca’s index allows only a rough estimation and applies to the range of intermediate body sizes to best; case of very large and very small body sizes of the BMI is more closely a limit observation can illustrate the Limitation:

How much should a person with 1 m height after Broca weigh? Broca’s ideal weight is at a very low height too low and too high at very large). Viewed graphically Broca’s ideal weight is a straight line, the body mass index is a function of body size a slightly curved curve (parabola).

Because particularities of each physique are ignored both BMI and Broca’s index are limited in their expressiveness. For example, has a bodybuilder a very low body fat percentage, but due to its high muscle mass may have a BMI of well over 25.