Your Body Has a Budget. Overdrafting Makes You Sick.
A new way to think about stress and health
You’ve probably been taught that the human body is like a thermostat: It measures whether something is above or below a certain set point, and if so, will employ some tactic to return it to its set point. For example, if it’s too hot, the body sweats to cool off — too cold, and the body will shiver to warm back up. The theory extends to other physiological features like blood pressure and blood sugar. This process — detecting a change and returning the body to some baseline — is called homeostasis, which comes from the Greek words for “the same” and “standing still.” Homeostasis, like the thermostat, is all about maintaining equilibrium, constancy, and stability.
But some experts argue that this theory of the human body is incorrect.
In a 1981 paper, neuroscientist Peter Sterling and epidemiologist Joseph Eyer, from the University of Pennsylvania, argued that “chronic arousal” was the source for the negative health effects associated with stress. Being aroused all the time caused the brain to “mobilize the mechanisms that produce energy for coping and suppressing the mechanisms that store energy” and let the body grow and repair. The duo hypothesized that the human body wasn’t striving to be stable, to meet a set point, like a particular blood pressure. Rather, it uses incoming sensory information to estimate the body’s state and anticipate what will happen next. If a demanding situation is predicted, then the brain marshals the body’s resources — changing blood pressure, secreting hormones, metabolizing glucose, and so on — to begin to meet those needs before they arise. It could explain why people who experience high levels of stress due to social issues like financial hardship, divorce, or racism, also have higher rates of diseases like hypertension, cancer, coronary disease, and, ultimately, earlier death.
Sterling and Eyer’s idea was revolutionary: The brain wasn’t controlling the body to react to the world. It was predicting the future and preparing the body for it. They named this concept allostasis, and it quickly found purchase among scientists who study stress.
The idea of allostasis has also revolutionized the understanding of why people have brains in…