# Area Mass Index

The Area Mass Index (AMI) is a parameter from anthropometry and represents the ratio of a person's body mass - measured in kilograms (kg) - to their actual body surface - measured in m² - whereby the body surface in turn depends on the individual physique (stature). and the gender of a person.

## Scientific background

The surface of a person's body is also the surface of his heat exchange with the environment. The heat generation of humans, which is necessary to maintain the body temperature , depends on the mass - more precisely on the muscle mass. The ratio of body mass to body surface area is not constant, but is determined by the body shape. Compact bodies always have a significantly smaller body surface area per kg of body mass than lean body shapes. In this respect, slim body shapes give off considerably more energy in the form of heat to the environment than compact ones, provided that the conditions of heat exchange (temperature of the environment, insulation through clothing, etc.) are identical.

## Definition of the AMI

The definition of the AMI was originally based on the evaluation of measurements of the actual body surface of test persons with the help of 3D body scans in cooperation with the Size Germany project . The mathematical evaluation of 188 data sets had shown at the time that the following formulas can be used to approximately calculate the AMI, based on body mass m (in kilograms) and body height H (in meters):

${\ displaystyle {\ mathit {AMI}} = 0 {,} 865 {\ frac {m} {H ^ {2}}} + 18 {,} 56}$ for women and
${\ displaystyle {\ mathit {AMI}} = 1 {,} 048 {\ frac {m} {H ^ {2}}} + 16 {,} 08}$ for men.

## Calculation of the body surface

The reciprocal of the Area Mass Index represents the specific body surface area of ​​a person, in the unit m² / kg. By multiplying it by the body mass, the surface area of ​​a person can be calculated in m².

## Further developments

As a further development of the AMI, the so-called AMI formula, also called AMI 2.0, has existed since 2014. This allows the precise calculation of the energy requirement of a healthy person on the basis of the AMI, taking into account the individual body composition and the activity profile of this person.

The Heat Performance Index (HPI) has also been developed. This is used to divide people into the following groups based on their heat dissipation to the environment: ultra high performers, high performers, ideal performers, low performers and ultra low performers. The Heat Performance Index can be calculated by any user with the help of anthropometric data (weight, height, fat percentage, muscle percentage).

## Individual evidence

1. E. Schlich, M. Schumm, M. Schlich: 3D body scan as an anthropometric method for determining the specific body surface. In: Nutritional review. 4, 2010, pp. 178-183.
2. E. Schlich: The AMI formula - 3D body scanning in online nutritional advice. 22nd Aachen dietetics training, 19.-20. September 2014. Association for Nutrition and Dietetics eV
3. E. Schlich: About the Area Mass Index (AMI) for the energy balance of humans. (= Nutrition and Consumer Education. Volume 2). Shaker Verlag, Aachen 2014, ISBN 978-3-8440-3202-4 .
4. http://www.area-mass-index.de/heat-performance-index/