Jeff Krasno
speaker
350 appearances
2 recordings
2 series
first heard Jan 2025
last heard Mar 2025
Jeff Krasno’s voice in public audio — every appearance, attributed to the second.
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Appearances
And that's totally normal. And that's good. Your heart rate and respiratory rate decrease. Your aperture opens back up. You become more trustworthy of the world around you. And that's great. That's adaptive. But I think in this culture... the rattlesnake almost never leaves the path. So we're constantly and chronically stressed.
And that's really the difference between how we experience bad, chronic, modern stress and what I would call sort of paleolithic good stress. And if you begin to actually look at the nature of stress, there are so many mechanisms in the human body that are adaptive.
I mean, if you were to go, let's say, to a high altitude, or if we were just to sit here and to, like, hold our breath for a while, might not be really great for the podcast, but... But over time, let's say if we held our breath for a minute, we would have sort of a glut of carbon dioxide. So that's called like hypercapnia and a dearth of oxygen. That's called hypoxia, right?
Now, too much hypoxia, and the podcast would meet an untimely end. Because too much hypoxia, your brain is not going to get enough oxygen, and you'll sign off one last time here on Know Thyself. But the right amount of hypoxia actually triggers this unbelievable adaptive response in the human body. So you have like these little chemoreceptors right here on the side of your carotid arteries.
And they say, oh my God, Andre's got a buildup of carbon dioxide. What are we going to do? Hey, make some more red blood cells down there because we need additional couriers. Stop doing that. We need additional couriers for oxygen because oxygen then gets shuttled to our cells and our mitochondria for energy production.
Our mitochondria then becomes hyper-efficient at making energy in hypoxic situations. Also brilliantly, carbon dioxide mitigates body pH balance. So your body's going to get a tiny bit more acidic if you hold your breath for a couple minutes. And that's totally adaptive because In that acidity, hemoglobin sort of loses its affinity for oxygen.
So hemoglobin is that little protein in the red blood cells that takes the oxygen and goes, okay, here we're going off to the blood cells. And if it's more likely to release it, that's better for energy production. So this is just like one of hundreds and hundreds of sort of pre-programmed adaptive responses to stress that exist in the human body.
But we've largely stripped all of those stressors out of the way that we live. So like, for example, like nutrient deficiency or calorie restriction is actually totally adaptive. It's really good for us. Not only does it keep... Andre nice and lean and lithe and a wonderful figure.
But also, it's activating certain metabolic pathways and other enzymes, et cetera, within your body. You know, there's a lot of scientists and medical experts wonks talk about like AMP kinase or whatever, these pathways for restoration and repair in the human body that stimulate these processes like autophagy and cellular cleanup and all this kind of stuff.
These processes were developed in relation to sort of paleolithic stress because in the olden days, you know, back in our hunter-gatherer days on the Serengeti, There would be a calorie paucity as part of winter, right? But now we live in this age where winter never really comes. So it's all calorie abundance all of the time. So the body is just really doing what it's meant to do.
It just stores fat away, you know, for a rainy day. But then there's no rainy day. And so this is like...
I think one of the greatest tensions that exist in modernity are these evolutionary mismatches, where we essentially evolved for a certain amount of stress, but since the Industrial Revolution and really accelerating over the last 50 or 70 years, we've engineered our lives at every single turn, often in the name of profit,
for ease and convenience and that ease is creating a lot of dis-ease and that convenience is creating candidly a lot of inconvenient truths that we have to grapple with.
Yeah.
Yeah, so I ended up coming up with this little acronym called the Big Macs. Not just the ones that you buy at the Evil M, but I really, I call it the Big Modern American Conveniences, so MAC. And, you know, there's, again, there are so many of them. But if you look at, like, I think the primary culprits that then create these mismatches, you know, I would say the number one is our food system.
So... starting in really after World War II, we started to see these massive escalations in obesity, right, in this country, and then other obesity-related diseases. That was this time where we started to essentially apply sort of a military industrial mindset to agriculture and to food. This was known as the Green Revolution. And, you know, candidly, it wasn't inspired by
for Machiavellian purposes, we needed to make enough calories to meet the needs of a very, very growing and escalating population. The problem was is that we started to create shelf-stable, nutrient-deficient calories, and in a surfeit of them, such that all that in the pump, and then you fast forward now, sort of in the palm of our hand, before this podcast would even finish,
We could literally order up any kind of food stuff in or out of season to your front door and have a feast. But this is, of course, like hijacking our own biology because we were meant to... Endure periods of scarcity like we talked about before. That kept us healthy. There's so many other examples. I think the other primary one would be just our sedentary lifestyles. Most of us sit at desk jobs.
I think in the United States, 80% of all jobs are desk jobs. So we're sitting, we're having these... eight, nine, ten hour periods of sedentariness, right? So we're not moving our body. This flies completely in the face of how we evolved. You know, we evolved moving all the time. We walked somewhere between on average, 7 to 10 miles per day.
So for people sort of managing steps on their iWatch, that's somewhere between 14,000 and 20,000 steps per day. Sort of just baseline level, you know? often against our will, we were forced into a full sprint, right? Sometimes being chased by an ungulate or whatever. And then we lifted and carried heavy things, right? We, you know, chopped wood and carried water, etc.
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