Whatever goes up must come down is a simple truth. Perhaps a corollary to that can be written. Whatever goes in must come out. It is surely so for the human organism.
Whatever goes in, comes out—one way or another. The human is, essentially, a thermodynamic system. It involves consumption, respiration, and elimination.
What Goes In
Let’s list everything that goes into a human in any given 24-hour period. Humans take in food, water-containing beverages, and air. We can ignore additional miniscule factors, such as sunshine. The oral cavity, the lungs, and even the skin participate in the input-output processes.
Must Come Out – Consumption, Respiration, Elimination
Solid waste is excreted via the bowels. Most of that waste-material is not water-soluble. This is because most water-soluble waste is excreted by the kidneys, through the bladder, to the urethra.
Of course, there is additional waste material. Digestion combines enzymes, acid, food, and moisture. However, some of the processing involves oxidation. Oxygen from the air is used to chemically oxidize the food. In addition to the solid and liquid waste already mentioned, there is gaseous waste.
Oxygen reacts with carbon in the food to produce carbon dioxide. And as everyone knows, carbon dioxide is a gas. How is that given off? It is given off by the lungs during the process of exhalation, along with unused air from the previous inhalation.
Finally, there are other sources of output. The purpose of consumption, respiration, elimination is two-fold. The oxidation process breaks down large molecules into smaller ones that are needed by the body to grow and to repair. Also, the body needs to maintain its internal temperature at approximately 98.6° Fahrenheit (37° Celsius). Energy “in effect” actually weighs something. Keep in mind Einstein’s equation,
E = m c²
This can be rearranged to read
m = c² / E
This indicates that the mass (related to weight) lost to produce the energy is equal to the square of the speed of light divided by the energy (calories) produced. The number is incredibly small, but it is real—it does exist. And that energy is gradually dissipated.
Now some may be inclined to include trimmed hair and nails, as well as exfoliated skin. Others may consider such substances part of the body. And let us include in this category the substances the bodies of men and women produce related to their gender.
So, how can one reduce his or her thermodynamic footprint? Unfortunately, output is the direct result of input. To lose weight, one must reduce input. Please don’t blame me in the comments section, below. At 300 pounds, I’m trying to discover some new law of physics that can help me change all of that.
Note: You might also enjoy Propane and Oxygen Combustion Question