Homeostasis is a governing principle underlying biological systems. As a biological system, the human body is a perfect example of a system that is governed by homeostatic principles.
Homeostasis is, quite simply, the tendency for factors within a system to fluctuate about a mean. Factors tend to stray away from the mean, only to be forced back towards the mean as they fluctuate too far. When a system is healthy, factors will naturally fluctuate within a set of bounds. A measure of an unhealthy system is one that can no longer maintain homeostasis – that is, a system that has lost its control over keeping its factors within a healthy range.
Biological systems are able to maintain homeostasis by way of feedback mechanisms. As factors tend to deviate too far from the mean, forces kick into gear that shift that factor back towards the mean.
Blood sugar is a great example of a system maintaining homeostasis. It is essential that blood sugar stays within a tight range, as elevated blood sugar (hyperglycemia) can cause life-threatening damage, and low blood sugar (hypoglycemia) is life-threatening due to the lack of energy available for certain life-supporting cells and tissues. To keep an organism alive, biological beings have developed methods for keeping blood sugar in check. The human body has a pancreas that senses the concentration of glucose in the blood, responding to elevated blood sugar with insulin (a signal to the body to take actions that decrease blood sugar), and responding to low blood sugar with glucagon (a signal to the body to take actions that raise blood sugar).
A second great example is the body’s store of fat in adipose tissue. Adipose tissue is a necessary part of the body. It not only serves as a depot for energy that can be used at any time, but also serves as a key sensor and signaler of the energetic state of the body. As adipose tissue fills up, it sends a signal (leptin) that tells the body to eat less, causing less energy to enter the body bringing the body’s total fat storge back down to normal.
With these examples, we see how it is natural for external forces to perturb the system. For example, when a meal is consumed, the body receives a load of blood sugar. It responds by releasing insulin to bring blood sugar back down, and afterward releases glucagon so that blood sugar does not drop too low. If the body receives too much energy over time, then fat stores tend to fill up, to which the adipose tissue responds by releasing leptin, causing the body to eat less, overall, allowing fat storage levels to drop back down.
However, it is possible for external factors to perturb the system too far. When this happens, it becomes difficult for the system to respond effectively.
Let’s take another example – that of a forest. Forests are filled with all sorts of life – various types of trees and other plants, a large variety of animals, and insurmountable bacteria, fungi, and other biological organisms. A forest is able to last over the centuries because of homeostatic principles. Deer eat the grass, which allows their population to grow. However, if they eat too much grass there is too little food to support the population, causing the deer population to drop back down (which allows grass to grow back). Similarly, wolves eat the deer, allowing the wolf population to grow. However, when the wolves have eaten too many deer they began to starve, causing the wolf population to go back down (and the deer population to go back up).
However, the occasional external factor (e.g. invasive species) can enter the forest and disrupt this natural flow. For example, a flea carrying disease may wipe out the deer population, causing the grass to overgrow and the wolves to starve. When this is the case, that ecosystem is not likely to return back to its state of homeostasis. Instead, it will evolve and eventually grow into an altered ecosystem with different species.
Again, the human body is another perfect example of a biological system. External factors perturb its internal factors, to which it responds, all the while keeping a healthy state of dynamic equilibrium. Occasionally an external factor will enter and cause damage that the body is incapable of responding to (e.g. viral infection). When this happens, the ultimate outcome is often the destruction of the system, unless the body can overpower that foreign invader.
This was the state of the human body as it evolved over millenia. The human body was self-sustaining – responding to dietary input, occasionally killed off by a pathogen (or serious trauma).
That was, until the industrial revolution set in, when the natural world transformed into a novel creation – one that has demonstrated itself to be not so suitable for supporting the natural homeostatic state of the human body.
The result is Modern Disease, the product of a human body incapable of regulating its own internal energy. When the body receives external inputs in the form of energy-dense, nutrient poor, toxin-rich substances, the internal network is overpowered. The natural design of this biological system has shown itself to be incapable of standing up to these strong perturbations, and the result is its gradual breakdown – a decline down a path of energy dysregulation, metabolic dysfunction, and ultimately modern disease.