Homeostasis, Hormesis, Survival Instinct, and Systems Approach

This article unpacks the nuances of [1] homeostasis, [2] hormesis, [3] the human survival instinct, and [4] a systems approach. I'll give a brief, plain-language definition of these terms and move quickly into why/how they matter. After reading this article, you'll better understand how these forces can work against your progress (swimming against the current) and how to harness them better to facilitate it (swimming with the current).

Homeostasis is a core organizing principle of human biology/physiology. While most are familiar with the term, it is often incompletely defined as a state of stability. More accurately stated, the essential concept of homeostasis concerns the process of maintaining stability. It is a self-regulating and automatic response to address changing external conditions. The homeostatic process drives major human systems, and our existence depends on tight regulation of ranges concerning temperature, blood pressure, hydration, blood glucose levels, and pH levels, to name a few. If we move toward a range's limit, our body reacts to counter the condition to regain and maintain stability.

Hormesis is a new term to most. Hormesis, loosely paraphrased, is the principle that "more is better—until it's not" and "less is better—until it's not." It is used when discussing 'dose-response' relationships. [Dose-response is the formal term describing the magnitude of a response to the exposure of an input, and we can use it in other contexts, too, such as exercise.] A classic example is describing the toxicity of a substance, like a pharmaceutical drug; there is often a lower limit under which the drug is ineffective and a ceiling over which the drug is toxic.

The human survival instinct, which we all likely understand, is that the human body prioritizes survival. We are, in essence, 'hard-wired' to remain alive, and our body will act, without a need for conscious thought or decision, to mitigate and eliminate external conditions or inputs that put us in danger. How our body reacts to poison (vomiting) and freezing temperatures (shivering and redistributing blood to vital organs) are simple examples; you can no doubt envision many others.

A systems approach (or 'systems thinking') is appreciating that complex entities—like the human body—are cohesive systems, not just a sum of individual elements. It is characterized by recognizing and exploring interrelationships, interdependencies, and feedback loops. This makes intuitive sense, but we often overlook this when we pursue our health and fitness goals.

So, why do these matter?

Let's look at some common scenarios. [The following examples are purposively simplistic to illustrate the concepts and how they work together. There are countless others, and these elements will play out repeatedly as we move forward. These are often a root cause for seeing—or not seeing—results in your efforts.]

While we may have an objective to lose weight, our body will fight our effort if we put it in mortal danger (real or perceived, it matters not). If we reduce our caloric intake too drastically, our body, sensing that we are starving, jumps into survival mode to protect us. Because we've moved toward or exceeded a range limit, it will attempt to bring us back into equilibrium. In the process, because activities in the body don't happen in isolation, we also inadvertently create a cascade of hormonal and other reactions. Not only are these unintended, but they directly counter our desired goal—to lose weight. We will not win this battle if we induce that type of reaction. Unfortunately, the outcome can be worse than just not losing weight: we may gain weight. Also, losing weight in the future may be more challenging because our body—again, with the intent of protecting us—has lowered our metabolism rate and moved to store more energy (fat) to prevent this condition (perceived starvation) from happening again. In short, this is why drastic diets based on severe calorie restriction fail or, if they 'are' successful, create other issues resulting from insufficient nutrients and muscle loss.

Let's view this through an exercise lens. You have been exercising constantly with no apparent or visible results, and your strength hasn't increased. In this instance, you may not be exercising at a level that is moving your body out of its normal homeostatic range. [In fairness, there may be other causes, too, but this example is solely intended to illustrate the point—not provide a comprehensive explanation.] If that's the case, your body isn't sensing a need to adapt or change to address your activity level. Using the same principles, we can modify an input (or combination of inputs), such as exercise intensity or duration, to push closer to a physiological limit. Simplistic examples would be walking at an incline on a treadmill until you were out of breath and couldn't continue (the technical term for this is 'volitional failure') or lifting a weight until your muscle(s) were unable to move the weight ('muscle failure'). In these examples, your body's systems (e.g., cardiovascular and musculoskeletal) would try to adapt to these stimuli to prepare you for their next occurrence.

A timeless example of a systems approach that will be a topic throughout this series is the nutrition, exercise, and rest/recovery triad. We often look at each of these pillars in isolation. In reality, each influences the others in very powerful and often overlooked ways. For example, if we fail to obtain enough quality sleep, we create an imbalance of the hormones that rule our feelings of fullness (leptin) and hunger (ghrelin), leading to cravings for sweet, rich, and fatty foods. We will also limit the extent to which we show improvements from exercising because we are not allowing our bodies to recover and adapt.

Hormesis can be illustrated using water as an example. We all know water is vital for life. Without water for a short period (days), we die. [Fun fact: body mass is approximately 55-60% water.] If we drastically overconsume water, we can enter into a state called 'hyponatremia' and also die (we throw off our heart's rhythm/function by causing a severe electrolyte imbalance). More interestingly, while we are not typically close to either end of this spectrum, even mild dehydration (losing just 1-2% of our body weight through dehydration) decreases physiological performance. Hormesis also relates to vitamins, supplements, and other substances. For example, vitamin D deficiency, common among all age groups, negatively affects immune function. Supplementing with too much vitamin D also leads to problems, including kidney function and a build-up of calcium in the blood (which is also an example of a system effect).

Key takeaways (the nuances):

• The body will respond to your actions, but not always in the manner you intend, and the responses are wider-ranging than you realize.
• Nothing you do to your body happens in isolation; there are always side effects and unintended consequences.
• It is common to view the body as a complex equation with one variable—the variable we choose to modify. In reality, the equation is not fixed; when we change the subject variable, the other parts of the equation change too.
• We can use homeostasis to our benefit by causing our body to adapt in the intended direction (e.g., getting stronger).
• We can limit the effects of homeostasis by not approaching our operating limits. This is why gradual weight loss and small daily caloric deficits are an effective body recomposition strategy.
• It's important to understand our body's operating limits better. Example: maximum heart rate (used to determine how vigorous your exercise is).
• In some instances, we can modify or shift the body's operating limits. This results from chronic adaptations to our interventions (changes that occur over relatively long periods).

In closing, as the saying goes, "Don't tell someone how to build a watch if they just want to know what time it is." I'm erring on sticking closer to helping you read the clock. That said, I am happy to provide more details if you're interested.