Stress and our body – Summary

“Most of us will have the luxury of dying of a stress-related

Our bodies seek homeostasis, the state where there is an ideal blood pressure, temperature, level of glucose in the bloodstream, and so on. A stressor can be defined as anything in the outside world that disrupts the homeostatic balance.

In philosophical terms: the highest good
In biological terms: Homeostatic balance
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

We, humans, activate the stress-response if being chased by a predator. But, critically, we can activate that same response if we merely think we’re about to be knocked out of balance — we have an anticipatory stress-response.
If there is no actual physical stressor impending, and we do that regularly,  we have entered the realm of anxiety, neurosis, hostility, and paranoia.
And if that occurs often enough our disease risk increases, because that is not what the stress-response evolved for.

Chronically diverting energy from storage sites increases the risk of metabolic diseases such as diabetes. Chronically increasing blood pressure or deferring growth, tissue repair, or reproduction can exact a health price.
In contrast to the situation with acute stress, chronic stress suppresses, rather than stimulates, the immune system, increasing the risk for infectious diseases. And chronically activating the stress-response can cause memory problems, increase the risk of depression and anxiety disorders, and even accelerate brain ageing. In other words, we humans are smart enough to make ourselves sick with thoughts, emotions, and memories — and we Westernized humans live long enough for the consequences to eventually haunt us big-time.

How does stress impact our lives? How does stress impact our health?

Not just any kind of stress: the psychological and psychosocial stress that we Westernized humans specialize in. If you’re a human, yes, stress can be when you’re knocked out of homeostatic balance. But a stressor can also be when you think you’re about to be knocked out of homeostatic balance. If you think you’re about to be knocked out of homeostatic balance and you’re really not, and you think that way all the time, there are medical ways to describe you:

You’re being neurotic, anxious, paranoid, or hostile1).

1) hostile
showing or feeling opposition or dislike; unfriendly.
“a hostile audience”
synonyms: antagonistic, aggressive, confrontational, belligerent, bellicose, pugnacious, militant, truculent, combative, warlike;

We, humans, activate the stress-response for reasons of psychological factors, and that’s simply not what the system evolved for. If you do that chronically, you’re going to get sick. The problem is that after a while, your stress-response is more damaging than the stressor itself, especially if the stressor was some psychological nonsense you made up.

Everything you’re doing with your body here is inefficient, but you got to do it because today is an emergency. If for psychological reasons, every day is an emergency, you never fix, you never grow, you never plan for the future. When you chronically turn on the stress response, your body is forced to ignore the repair and growth functions it would normally be performing, and then you’ve got this big challenge of how do you recover afterwards?

So what happens when you do all of this for too long because of chronic stress, especially chronic psychological stress? Increase your blood pressure for 30 seconds and run away from the lion — you’re saving your life. Increase your blood pressure chronically, and you are suffering from hypertension, which could lead to damage to your blood vessels. Very interesting research shows that if you couple hypertension with a high-fat diet, you get far more vascular damage than either alone.

Let’s now think about chronic stress. You’ve got someone who says, “Oh my God, I’m so stressed. I get stuck in traffic every day, I have a horrible boss, my relationship is unsteady, all of these sorts of things, and I am like totally stressed nonstop, 24-7.” This is not like totally stressed nonstop 24-7. You want to know what totally stressed 24-7 is about, you look at somebody with a whole body burn, and you look at somebody in septic shock. That’s stress 24-7. … What we call everyday chronic stress is instead lots and lots of intermittent stressors.

What does stress have to do with child development?

The critical fact is that the environment doesn’t begin at birth. Environment begins in fetal life, and thus the consequences of stress can begin in fetal life also. What’s environment like for a fetus? What it’s about is what mom is experiencing, because you share her circulatory system, and the hormones in her bloodstream will wind up, to some extent, in your own circulatory system. The amount of nutrients is relevant, as are things like extremely loud noises.

It’s the same outcome in a child as opposed to a fetus. Chronic activation of the stress-response does all sorts of bad stuff. If you stress an infant rat, you produce an adult rat with higher glucocorticoid levels and who has trouble turning off glucocorticoid secretion at the end of stress. Your rat will have a somewhat activated stress-response all the time and be more vulnerable to relevant diseases. Your rat will be not as good at learning and memory and will be more prone toward anxiety. Chronic stress leads to all sorts of long-term consequences.

The other component that comes into the equation is mothering style. Different styles of mothering can represent and generate a more stimulatory environment, or a less or more stressful one. Studies on rats and primates have shown that mothering style translates into different adult stress-responses in the offspring. So experience, prenatal and postnatal, can shape the sort of hormonal profile and brain you have as an adult. Early experience—taking the form of severe stress, but also mild stress, degrees of stimulation, and mothering style—produces different profiles in adulthood, and even in following generations.

What impacts does stress have on our body?

There are basically 3 constituents in food: protein, carbohydrates, and fat.

Your stomach and intestines do their thing, breaking down protein into amino acids, breaking down complex carbohydrates into simple sugars, and breaking down fat into fatty acids and glycerol. You are well fed: You’ve got if anything, surplus amounts. What do you do? You store the stuff away in a complex storage form. You do exactly the opposite of the digestion that you have just gone through.

Another potential problem is diabetes. If you’ve got juvenile (Type 1) diabetes and are chronically stressed, this starts a vicious cycle. Each time you get stressed, you’re releasing a flood of sugar into your bloodstream and then storing it away. You are doing the very opposite of what blood sugar control is about in diabetes: You’re getting huge oscillations all over the place. Chronic stress makes a glycemic control (control of sugar) more precarious for a person with diabetes. Type 2, or adult-onset, diabetes is coming to haunt modern Western societies. The problem here isn’t too little insulin; it’s an excess of nutrients. Typically, you are getting older in a Westernized way: You put on weight, you become more sedentary, and you’ve got all these excess nutrients in your bloodstream. What’s the logical thing you would be doing at this point? Store away the excess. But your problem is you’ve stored so much away already that your fat cells are full. One additional step occurs: Your brain indirectly sends a signal to the fat cell storage sites throughout your body and says, “Don’t listen to any insulin. Become resistant to it; lose your sensitivity to it.”

This insulin resistance can lead to hyperglycemia, which can lead to cardiovascular damage and increase your risk of metabolic disease. Suddenly, they are completely intertwined, which is the rationale behind the large catchment term for what can go wrong in this realm, metabolic syndrome. Metabolic syndrome encompasses an array of symptoms that increase your risk of metabolic disease and/or cardiovascular disease.


We, as humans, have, quite similar to the zebra, the same capability to react and handle stressful situations. But while the zebra gets back to balance after the successful escape from the lion, we like to keep staying in the alert stage. As described above, it is enough to think that we might get hunted to trigger the stress-responses.
In other words: the more we are focusing ourselves on being stressed, the longer we keep the stress-responses activated, the higher the physical and mental damages become. We can handle stress, but only for a short period of time.
Therefore, it is essential for us to get back to a homeostatic balance as soon as ever possible and as often as we ever can.


abdominal fat: Fat deposits around the gut. Chronic stress preferentially
promotes the deposition of abdominal fat, which is of the type that is worse for cardiovascular health.

gluteal fat: Fat deposits around the buttocks.

Helicobacter pylori: A bacteria that causes a large percentage of cases
of peptic ulcer. Chronic stress can impair the ability of the body to repair
such ulcers.

ulcer: An area of tissue erosion (e.g., on the skin or on the stomach lining).

Cushing’s syndrome: A collection of diseases involving pathologically
elevated levels of glucocorticoids.

frontal cortex: The brain region involved in decision making, impulse
control, long-term planning, and gratification postponement.
post-traumatic stress disorder (PTSD): A psychiatric disorder comprising
a constellation of symptoms (e.g., sleep disruption, flashbacks, and
hypersensitivity to stimuli) caused by severe trauma (e.g., combat trauma,
childhood abuse, or rape).



Course Guidebook
Stress and Your Body

written by
Professor Robert Sapolsky
Stanford University

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