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Global Translational Medicine Mass balance

increase (i.e., absorbed mass > oxidized mass) or decrease however, when the nutrients are eliminated from the body
(i.e., absorbed mass < oxidized mass). either as products of metabolic oxidation or in other forms
More specifically, energy balance can occur at body (e.g., shedding of dead skin cells).
mass stability only if the following three conditions are Animals, including humans, ingest food to obtain
simultaneously satisfied: energy and mass. While energy refers to the capacity to
(i) Average absorbed fat mass = Average oxidized fat mass; do work, mass is used to build all bodily structures. Not
(ii) Average absorbed carbohydrate mass = Average a single gram of body mass is added through energy
oxidized carbohydrate mass; intake. Since calories represent the heat release upon food
(iii) Average absorbed protein mass = Average oxidized oxidation, they have no impact on body mass [1,3] . The term
protein mass. “calorie” comes from the Latin term calor (heat). Calorie is
broadly defined as the amount of energy needed to increase
Clearly, this can never happen. If, for example, all the the temperature of 1 g of water by 1°C. Heat certainly does
absorbed protein mass (amino acids) is oxidized, where not produce mass.
would the body get building blocks? Therefore, energy
balance is unattainable at body mass stability [1,3] . This fact The protons and neutrons (i.e., nucleons) that make up
refutes the core idea of the EBT, that is, body mass remains an atom account for nearly all of its mass; nuclei contain
constant in energy balance. >99.9% of the mass of an atom. Countless chemical
reactions constantly take place in the human body, and
To explain clearly, this section highlights that the energy is bound or released in them. In all these reactions,
following textbook argument is fallacious: only electron clouds undergo changes. Atomic nuclei,
When a person is in energy balance, his/her weight stays therefore, always remain intact; changes to the nuclei
the same. only occur during nuclear reactions. Body mass can only
change as a result of net mass flow [1,3,6] ; thus, the only food
On the contrary, textbooks should read the following: property that can augment body mass is its nutrient mass,
When a person is in energy balance, his/her weight does not its energy content (i.e., calories). Like gravity, this is by
not stay the same. Since this concept can be difficult no means a matter of opinion.
to understand, more attention should be paid to the It inevitably follows that any anti-obesity intervention
matter. However, the energy balance theory should be must decrease the intake of energy-providing mass,
also understood since it is important to know what has increase the elimination of oxidation products, or both.
been known before so that one can quickly grasp new
information. (i) Decrease intake of energy-providing mass (EPM)
(“Mass In”), that is, satiating effect. EPM refers to the
6. Regulation of body mass daily intake of carbohydrate, fat, protein, soluble fiber,
and alcohol.
At this point, it should be clear that the regulation of body
mass is entirely about detailed mass balances (“Mass In, (ii) Increase elimination of oxidation products (“Mass
Mass Out”) rather than energy conservation (“Calories In, Out”). Each day, we experience weight loss (i.e., body
Calories Out”). The Law of Conservation of Mass guarantees mass loss) given by the weight of energy expenditure-
that (i) the O mass that enters cellular respiration plus dependent mass loss (EEDML) plus the weight of
2
[3]
(ii) the mass of macronutrients that served as energy energy expenditure-independent mass loss (EEIML) .
fuel must be equal to the mass of the excreted oxidation EEDML refers to the daily excretion of EPM oxidation
products. This is not a matter of opinion. Daily weight loss byproducts (CO , water, urea, and SO ), whereas
2
3
must, therefore, be the result of the daily elimination of EEIML represents the daily weight loss resulting
oxidation products (CO , water, urea, sulfur trioxide [SO ; from (a) the daily elimination of non-metabolically
2
3
“Mass Out”) rather than a consequence of the heat release produced water; (b) minerals lost in sweat and urine;
upon nutrient combustion (i.e., daily energy expenditure) (c) fecal matter elimination; and (d) the mass loss
[3]
[5] . It is macronutrient mass intake (“Mass In”) that augments from renewal of skin, hair, and nails .
body mass; as dictated by the Law of Conservation of Mass, A recently proposed mass balance model (MBM)
[3]
the absorption of 1 g of glucose, protein, or fat increases describes the temporal evolution of body weight and body
body mass by exactly 1 g, independent of the substrate’s composition under a wide variety of feeding experiments,
calories. The absorbed nutrient mass cannot be destroyed, and it seems to provide a highly accurate description of
and thus will contribute to the total body mass as long the very best experimental human feeding data [1,3,7,8] . For
as it remains within the body. Such a contribution ends, example, head-to-head comparisons of the predictions by

Volume 2 Issue 1 (2023) 4 https://doi.org/10.36922/gtm.222