high-resolution terminology - matching measurements at high-resolution

Body mass

## Description

The body mass M is the mass (kilogram [kg]) of an individual (object) [x] and is expressed in units [kg/x]. Whereas the body weight changes as a function of gravitational force (you are weightless at zero gravity; your floating weight in water is different from your weight in air), your mass is independent of gravitational force, and it is the same in air and water.

Abbreviation: m [kg]; M [kg·x-1] Healthy reference population Body mass excess BFE BME cutoffs BMI H M VO2max mitObesity drugs

```Communicated by Gnaiger Erich (2020-02-15) last update 2020-07-05
in: Catastrophe XXX XXX-mass Carol on BME and mitObesity of X-mass Carol
```

## Body mass and body tissue mass versus mass of a tissue sample

1. M [kg/x]: The SI unit for mass (of a system), m, is [kg] (1 kg = 1000 g). The body mass M is the mass, m [kg], per individual. The individual (object X=Body, abbreviated as X=B) is the unit-entity UX = UB. The unit-entity is the count NX of a single object NX=1 [x]. The individual (object) UB is a countable quantity. The number of individual objects is the quantity count NX, with the unit [x] as the elementary unit for the number of unit-entities. Accepting to write the unit [x] for the countable number of objects X explicitly, then the unit of M = m/NX is [kg/x]. The average body mass M in a population can be obtained theoretically in two ways: (1) M can be measured for each individual of a large sample and expressed as the average of N measurements. (2) The total mass, m [kg], of NX [x] individual objects can be obtained in a single measurement, and the average body mass per individual is then calculated as M = m/NX [kg/x]. Of course, the second approach is not practical for humans, but is typical for cultured cells or small animals, such as nematodes. It is suggested to use the upper case letter M as the symbol for the quantity mass per object. The term elementary mass may be considered for the mass per unit-entity.
2. M versus m: The SI symbol m is used to indicate the mass of a system or sample [kg], whereas the symbol M is used to indicate the mass per individual (object) [kg·x-1]. A system is not a countable quantity and thus is not a number. Both, (elementary) body mass M [kg/x] and mass of a sample m [kg] are extensive quantities, which depend on the size of the individual or the sample. The mass of a tissue (e.g., muscle or fat) is of interest in two contexts: (1) The tissue (muscle, M) mass obtained from a biopsy, mM [kg] or [mg] of wet or dry tissue mass; and (2) the total muscle or fat mass per individual object, MM or MF [kg/x]. The extensive quantity m is frequently confused with the quantity weight, which is a force. The term 'body weight' is common, due to the practical sensory experience of heavy or light things. The terms 'massive' and 'heavy' may not be well discerned in practical language, since mass is a rather abstract concept and practically felt as a weight (see Canon X: Taking part in an X-mass party).

## Human body mass

The elementary body mass of a human is measured without outdoor clothing (in light underware or swimsuit and without shoes) standing upright on a firm horizontally leveled and calibrated balance. This SOP applies to mobile persons who can stand steadily for the measurement. Some studies apply rigorous standards: 'All measurements were done at least 3 h after a meal (including drink), and subjects were requested to refrain from strenuous exercise 12 h prior to the measurements. Subjects were asked to empty their bladder before the measurements. Females were not measured during their menstrual period' (Deurenberg 2001 Eur J Clin Nutr).
The elementary body mass is the sum of (elementary ) lean body mass and fat mass, M = ML + MF, or the sum of the reference body mass of an individual at a given height in the healthy reference population and excess body mass, M = M° + ME. The excess body mass, in turn, is the sum of excess lean and fat mass, ME = MLE + MFE. The body mass excess BME is normalized for the reference body mass, BME = M/M°.

## Self-reported measurements

'Men overestimated their height by 1.3 to 1.9 cm and the women by 0.5 to 1.3 cm. Men overestimated their weight by up to 0.45 kg and women underestimated their weight by up to 1.4 kg' (Tipton 2012 Nursing).