The Misunderstood Science of Metabolism
Buy book - Burn by Herman Pontzer
What is the plot of the Burn book?
The documentary Consume (2021) sheds light on the physics underlying metabolism - the process through which our bodies burn energy. It is jam-packed with memorable ideas and information, and it relies on the most recent metabolic research as well as the evolutionary history of the human body to create a compelling narrative.
Who is it who reads the Burn book?
- Members at the gym are perplexed as to why they aren't losing more weight.
- A prospective dieter who is uncertain about which dietary plan to adhere to
- Naturalists who are interested in the history of nature
Who is Herman Pontzer, and what is his background?
The Duke Global Health Institute is home to Herman Pontzer, Associate Professor of Evolutionary Anthropology at Duke University, as well as an Associate Research Professor of Global Health at the Duke University School of Medicine.
What exactly is in it for me? Learn how the human body functions in its most basic form.
The human body is made up of about 37 trillion cells. Each one functions as a mini-factory, churning out all of the stuff that keeps us alive, from enzymes to neurotransmitters to hormones and everything in between. The calories we eat give the energy that allows us to carry out our tasks. It takes eight liters of cold water to get to a rolling boil in our bodies every day, and our cells consume enough energy to do so. As a result, energy is the currency of life. However, metabolism — the mechanism that regulates energy use – is often misunderstood. It's past time to make a difference. Among the topics covered in these notes are what Tanzanian hunter-gatherers can teach us about human evolution, how sharing food distinguishes humans from monkeys, and why you can eat nothing but candy bars and yet lose weight.
You are, very simply, what you consume.
In 1859, the French scientist Louis Pasteur created a revolutionary broth that changed the course of history. What was it about it that made it so special? First and foremost, Pasteur discovered that boiling the soup destroyed any germs that may have been present in the liquid. And, second, he discovered that storing it in an airtight flask prevented bugs and dirt from getting into the flask. This two-step method kept the soup from deteriorating, which was a groundbreaking finding at the time of its invention. Pasteurization is the term used to describe this process, which was named after Pasteur himself. The project was not just a resounding success in terms of practicality, though. It also served as the last nail in the coffin of a theory that had been around since Aristotle — the idea of spontaneous genesis.
The theory of spontaneous generation attempts to explain occurrences such as the appearance of maggots on decaying meat at an unexpected time. We don't know where all these maggots came from. Before the advent of strong microscopes, it was difficult to provide a satisfactory response to this issue. Everyone from antiquity through the Middle Ages and far into the modern day said that they sprang out of nowhere — that is, that they emerged spontaneously from inanimate things such as flesh. The reality of metabolism has been revealed by over a century of study, and it is much weirder than we could have imagined when we started. The most important lesson in this letter is that you are what you eat - very literally.
Today, we know that maggots do not develop from inert materials, as previously believed. Take a closer look at a maggot-laying fly, on the other hand. What exactly does it do? This tiny machine, in its most basic form, is responsible for the transformation of rotting protein into baby flies. To put it another way, it builds the bodies of both itself and its progeny out of water, air, and the food it eats on its own initiative. Humans, like flies, are spontaneous-generation machines that generate ideas on their own. Every ounce of bone and pint of blood, as well as every fingernail, eyelash, and strand of hair, is composed entirely of the substances we consume in our diet. It has been discovered that inanimate matter can generate life.What caused this strange change to take place? The solution is metabolism, which is the process through which our bodies burn energy. Let's take it step by step.
The human body is made up of hundreds of distinct molecules that interact with one another. Enzymes, hormones, neurotransmitters, DNA, and a variety of other substances fall into this category. However, only a small percentage of them gets absorbed into the body in a useable form via our meals. It is necessary to convert them before they can even be put to good use. This is the result of the work of cells. Cells have the responsibility of drawing in helpful chemicals flowing into the circulation via their membranes and converting those molecules into something else. Take, for example, ovarian cells. In this process, they draw cholesterol molecules into the body, convert them, and then push the final result back into circulation as estrogen, a hormone that has effects throughout the body.
It is the work of these cells that allows us to survive. However, it requires a significant amount of energy. Methylation, also known as metabolism, is the body's life-sustaining furnace, "burning" our food and releasing its energy for this reason.
The rate of metabolism is a measure of the body's energy expenditure.
Cells are active and need energy to function properly. But, more importantly, how are we defining these terms? It is really possible to use the two ideas interchangeably. Work is a technical word in the field of physics. Furthermore, since labor and energy are both measured in the same units, we may interchangeably refer to them. To put it another way, labor is energy. When you toss a baseball, for example, you are exerting effort, which is what causes the ball to accelerate. When the ball leaves your hand, the energy you use in throwing it is transformed into kinetic energy, which is the energy expended by the ball as it travels through the air. Heat is another type of energy that we encounter on a daily basis. As an example, when you reheat milk in the microwave, the temperature rises and indicates how much electromagnetic energy the milk has absorbed.
The amount of energy used is always equal to the amount of labor done and the amount of heat generated. Because this is a basic rule of physics, it follows logically that it controls the human body as well. The main point to take away from this remark is that metabolism is a measure of the body's energy expenditure. When it comes to objects that have the ability to perform labor or generate heat, energy may be stored. A good example is gasoline stored in a fuel tank.The same may be said about a stretched rubber band, which contains a kind of potential energy known as "strain energy." Meanwhile, a large plant pot that is dangerously balanced on a window ledge and has the potential to come crashing down at any time possesses kinetic energy.
At the molecular level, the bonds that keep molecules together serve as energy storage devices. This energy may be transformed into something else. However, it is irretrievably gone. During the release of a stretched rubber band, the molecular connections break apart, releasing the energy stored in the rubber band into the surrounding environment. It is a natural rule that energy can never be lost, but can only be transformed.
Explosions are a magnificent illustration of this rule in action. Take nitroglycerin as directed. This volatile liquid's chemical connections are broken when it is detonated, resulting in the release of energy in the form of nitrogen, carbon monoxide, oxygen, and water. How much is it, exactly? The energy contained in a pound of nitroglycerin, if turned into heat, has the potential to completely destroy a human being — which is exactly what strong bombs are capable of doing. However, if turned into kinetic energy, it has the capability of launching a 165-pound adult more than two and a half miles into the atmosphere. You may be wondering how this relates to metabolism.
After all, if energy and work are interchangeable, then the work that our cells do and the energy that they consume are two different measures of the same thing. The term "metabolism" refers to the process of converting food into energy. Whatever word we choose, we're looking for the most basic action of the body. When we include speed in the equation, we can calculate the body's metabolic rate, which is the amount of energy the body expends per minute to fuel the work of its cells.
It all comes down to counting atoms when it comes to tracking energy consumption.
What method do you use to calculate your energy expenditure? In principle, it's straightforward: you just follow the CO2. No matter what fuel is used, whether it is coal or carbohydrates, the combustion of fuel produces a byproduct: carbon dioxide. When the body consumes energy, CO2 is released into the atmosphere. When you take a breath, you are mostly exhaling this substance. As soon as you figure out how much CO2 the body generates, you'll have an exact assessment of how much energy the body is using. To monitor CO2 levels, one method is to put a person in a metabolic chamber, which is a sealed room equipped with sensors that measure oxygen and carbon dioxide levels. Although reliable findings may be obtained in a controlled setting, what we actually want to know is how much energy individuals spend on their daily activities. Among the most important messages included in this letter are the following: Tracking energy consumption is all about counting atoms.
An inconspicuous technique for monitoring CO2 production in individuals going about their daily lives was developed in the 1950s by Nathan Lifson, a physiologist at the University of Minnesota who worked as an assistant professor of biology. Lifson's discovery started with the observation that the human body, which is composed mostly of water (65 percent), is essentially a vast pool of liquid. There is an influx and an outflow of information. Atoms of hydrogen and oxygen enter the body via food and drink, and they exit through urine, feces, perspiration, and the vapor exhaled by the body when we are breathing. Hydrogen atoms usually leave the body in the form of water, while oxygen atoms have a second method of leaving. In the process of metabolizing carbon-based compounds, CO2 is produced. In this newly formed CO2 molecule, the oxygen atom comes from the body's own water. This atom is subsequently expelled into the atmosphere as CO2 in our exhaled breath.
Lifson discovered that monitoring the pace at which hydrogen and oxygen atoms left the body enabled him to compute the rate at which CO2 was being produced, which in turn allowed him to determine how much energy had been used. It is necessary to do some complicated chemistry in order to trace these atoms, but the fundamental concept is to "label" them. Specifically, you inject hydrogen and oxygen isotopes, which are heavier versions of hydrogen and oxygen, into the body to do this. Once the isotopes have left the body, you may count them by examining urine samples taken at various times. Deuterium is an isotope of hydrogen, and if 10 percent of the hydrogen in a subject's body was deuterium on Monday, but only 5 percent was deuterium on Wednesday, it is obvious that half of the body's water has been evacuated and replaced with normal H2O. It's the same as oxygen-18, which is an isotope of oxygen.
Calculating the rate at which hydrogen and oxygen atoms are lost from the atmosphere allows you to determine the rate of CO2 generation based on this data. This, in turn, serves as an indicator of how much energy – or, more specifically, how many calories – the body has expended.
In a figurative sense, we are no different from our forefathers.
What is it about Westerners that makes them so fat? According to one popular idea, it goes like this. When the earliest Homo sapiens lived in the habitat that we now call Africa, the human body, particularly its metabolic system, developed to be able to deal with that environment. Food was limited, and these hunter-gatherers had to spend enormous amounts of energy in order to locate what little was available. The idea argues that industrialisation, which has provided us with automobiles, office jobs, and supermarkets, is to blame for our current obesity epidemic. We are not nearly as physically active as our forefathers and foremothers, which means that we are not making the most of our bodies in the way that they were intended to be utilized. It's no surprise that we have metabolic problems! Although it is a compelling hypothesis, fresh data indicates that it is incorrect. The most important lesson in this letter is that we are, in many ways, no different from our forefathers.
If you believe that the Western world's obesity epidemic is due to the fact that we are burning less calories per day than our ancient forefathers, how can you verify or refute this claim? Although it is easy to determine how much energy the typical American or Italian expends on a daily basis, we are unable to go back in time to examine the metabolic systems of early people. We can, however, do the next best thing, which is to look at the energy consumption of contemporary individuals who live in the same manner that we do.
Take, for example, the Hadza people of northern Tanzania, who constitute one of the world's few surviving hunter-gatherer groups. Their lifestyle is strenuous on the body. Hadza women spend most of their days digging tubers out of the rocky soil and collecting wild fruit from the forest. Men, on the other hand, go about twelve kilometers across the sun-baked savanna, searching for animals and climbing 40-foot trees to get wild honey. In the evenings, the Hadza people congregate around campfires to enjoy the products of their work and to tell stories about their lives. What kind of energy do they consume? In order to find out, the author and his colleagues submitted Hadza urine samples to a specialized facility in Texas for analysis. According to popular belief, Hadza men and women should exert much more energy than their sedentary Western counterparts in order to survive. However, the outcome did not meet expectations.
Hadza males consume and expend about 2,600 calories per day, whereas Hadza women consume and expend approximately 1,900 calories per day. That's precisely the same number of calories that men and women burn on average in Europe and the United States, respectively. Compared to someone commuting to an office job in New York or Naples, a Hadza hunter-gatherer has significant variations in lifestyle. However, in terms of energy consumption, they are completely non-existent.
Humans have a metabolism that is either restricted or fixed.
Is it possible that the Hadza findings are a strange anomaly? No, not at all. Consider the findings of a 2008 study conducted by Amy Luke, a researcher at Loyola University Chicago. Women residing in rural Nigeria were compared to African American women living in Chicago using the Lifson technique, which Luke used to determine their energy consumption and physical activity. Despite the fact that they lead totally different lives, it was discovered that both groups spend the same amount of energy on a daily basis. Then there's Lara Dugas, another Loyola scholar who's worth mentioning. She compared data from 98 different research conducted all around the world. What was her conclusion? Individuals who have sedentary lifestyles in the industrialized world expend about the same amount of energy as people who lead lives that are much more physically demanding in the developing world. It turns out that people are very similar wherever you go when it comes to energy use.
The most important lesson in this note is that humans have a limited or set metabolic rate. How is it that the Hadza spend their days outside gathering, hunting, and climbing trees without expending any more calories than sedentary Western urbanites remains a mystery to us? Most likely, a number of variables are involved in this situation. One element of the explanation is that individuals who are very active, such as the Hadza, gradually alter their behavior in order to save energy. This may include sitting rather than standing, or sleeping for a longer period of time. When we participate in a lot of physical activity, our bodies also "budget" their energy consumption in a different way.
Typically, the majority of the calories we expend are used to fuel the activity of our cells and to perform cellular "housekeeping," which includes mending the damage done to our bodies by daily activities. It seems that by reducing the amount of time spent on these activities, the body is able to free up more energy for other activities. Evidence suggests that exercise may reduce the immune system's inflammatory response as well as the synthesis of hormones such as estrogen, among other things.
In addition, we know that at greater levels of exercise, energy consumption reaches a plateau. Take, for example, the research performed by the author and Amy Luke in collaboration. They gave the Lifson test to 300 individuals and used fitness trackers to measure their activity levels over the course of seven days. As a consequence, what happened? Everyone, even those with the most highly active daily lives, burnt the same amount of calories each day as those who were just moderately active. Taking all of this data into consideration, we may reach an intriguing conclusion: our species has developed methods for keeping our daily energy consumption under control. This has far-reaching consequences for the public's health. The fact that our daily energy consumption has been constant throughout human history means that obesity can not be blamed on our sedentary lives. To put it another way, it is gluttony rather than laziness that is responsible for our obesity.
Our evolutionary past helps to explain why humans are so prone to being fat in the first place.
Natural history, according to Charles Darwin, is formed by the fight for resources in the environment. The evolution of species occurs under circumstances of scarcity, since there is never enough food for all of them. It is for this reason that trade-offs are so essential. You can't have it all because you don't have enough energy. In the case of evolutionary characteristics, such limits are readily apparent. Perhaps evolution gives a species razor-sharp teeth, but at the same time, it supplies the species with small, delicate arms. That is how you get a Tyrannosaurus rex skeleton. As Darwin phrased it in The Origin of Species, "nature is compelled to economize on the other side of the coin in order to spend it on the other side." There is one species, however, that does not adhere to this principle: our own. Throughout this note, the main point is that our evolutionary past helps to explain why humans are so prone to fat.
When it comes to energy use, humans are overindulgent. Take, for example, the differences between ourselves and our nearest cousins, the chimpanzees. When you take into consideration factors such as body size and activity level, humans eat about 400 more calories per day than chimpanzees and bonobos. What are we going to do with all of these additional calories? After all, just maintaining one's physical health is a costly endeavor. Take the brain, for example. It consumes so much energy that every fourth breath we take is dedicated to supplying this three-pound organ with nutrients. As compared to apes, we also breed more often, have bigger kids, live longer lives, and travel more. Are there trade-offs to be made? Sure, the human digestive system is smaller and less expensive than that of the majority of apes, but that's about all there is to it.
Biologically, our bodies have evolved to burn more energy at the cellular level. This was nothing short of a metabolic revolution, but it was not without its drawbacks as well. As our forefathers' metabolisms became more rapid, the likelihood of their starving rose as well. After all, the more energy you need to operate, the worse it is when your food supply is depleted. The evolutionary answer to this issue has been a source of fascination for us to this day.
Keeping an energy-guzzling machine like the human body fuelled in an environment characterized by scarcity is the most straightforward method of ensuring that it continues to operate. The fat cell serves as the body's primary fuel storage system. This distinguishes humans from apes as well. If you keep a chimpanzee in a zoo with plenty of food, it will grow to be larger than its wild cousins, but it will retain its thin appearance. Extra calories lead to the development of larger muscles and organs rather than the accumulation of fat. Humans do gain weight under comparable circumstances — and it's no surprise! In reaction to food scarcity, humans have evolved, but we now live in a world of caloric plenty, and we must adapt. That is the true misalignment between our physical bodies and our social environment.
The metabolic revolution was fuelled by the act of sharing.
Humans and apes have a number of characteristics, including the fact that they are both sociable creatures. Of course, there are a variety of other characteristics that distinguish us. Things like metabolism come to mind. What is the root reason for this divergence? And how come the human metabolic system outperforms that of the apes?!!The simple explanation is that people share food — while apes don't share their food. The more detailed response is as follows. Despite the fact that apes are capable of establishing complex and even lifelong social connections, they are rugged individualists when it comes to food consumption.
This influences the way people approach the task of calorie counting. Because their existence is dependent on it and no one else is willing to assist them, they take advantage of the low-hanging fruit — both literally and figuratively speaking. It makes little sense to collaborate with others to hunt large animals or collect enough fruit for a week if you aren't willing to share. That was eventually the stumbling block for the apes. Shared resources drove the metabolic revolution, according to this note's main theme. Our forefathers and ancestors were foragers who lived in groups. When they were full, they didn't stop the search for calories, but instead brought back food for the rest of the group to eat.
Shared responsibility provides a safety net. No matter how much food you get from someone, if you return to your camp empty-handed, you will still be able to feed yourself and your family. Human behavior is altered as a result of this safety net. It allows you to take calculated risks, such as sending men out to hunt animals with the knowledge that they will fail nine times out of ten. The ladies, on the other hand, have been busy for the last several hours collecting tubers and berries, so there is more than enough food for everyone. And when the guys are successful in bringing a wildebeest home, there will be a celebration.
Approximately two and a half million years ago, ape-brained hominins living in eastern Africa developed this social structure, according to current theories. We don't know much about the beginnings of sharing, but there is plenty of evidence of it in the more recent past, which suggests that it was widespread. For instance, zebra bones with cut markings are an excellent illustration. It takes a team to bring down a big, quick animal like a zebra, and cooperation only makes sense when everyone gets to participate in the rewards.
Social foraging has altered the course of humanity's evolutionary history. Sharing meant that there was more energy available for the important activities of life. It was a time of increased survival and childbirth, as well as increased time spent experimenting with primitive technologies. who shared their resources outperformed those who did not. After a long period of time, the human body as we know it starts to take form. The rate of metabolism increased, resulting in the development of the equipment that would eventually support the energy-guzzling organ that distinguishes us as a species — the brain.
Any food will suffice as long as you're burning more calories than you're consuming to lose weight.
Let's review what we've learned thus far. According to metabolic studies, contemporary urbanites who drive automobiles and sit in comfortable office chairs expend as many calories as hunter-gatherers. In other words, it is probable that daily energy consumption has been constant throughout the Paleolithic period of evolution. As previously said, we know that our daily energy expenditure is limited, which implies that increasing the quantity of activity we do has minimal impact on the number of calories we spend. What are our options in light of these findings? They contend that it is past time to reconsider our approach to combating childhood obesity. For the most part, exercise has little effect on our weight, but managing our meals has a significant impact. You can eat anything and still lose weight as long as you are burning more calories than you are consuming, which is the main point of this letter.
Regular exercise offers a slew of well-documented advantages, ranging from better heart health and immune system strength to improved brain function and longer life expectancy. It also offers the added benefit of suppressing chronic inflammation, which has been related to both cardiovascular disease and autoimmune diseases. Exercise, on the other hand, is not a very helpful strategy when it comes to weight control. A poor diet, as the old saying goes, is something you can't escape. This leads us to the topic of diets. Given the amount of hype around this subject, let's get straight to the point: if you want to lose weight, you need to burn more calories than you eat on a daily basis. That is just a fundamental rule of physics.
The good news is that you now have complete freedom to choose the diet that best suits your needs. Consider the findings of the 2005 research conducted by Michael Dansinger, who is now the director of the Diabetes Reversal Program at Tufts Medical Center in Boston, Massachusetts. His team randomized 160 individuals from Boston at random to one of four popular diets over a period of twelve months. These were based on a variety of dietary "philosophies." For example, Atkins is a low-carb diet, while Ornish is a low-fat diet. The other two programs, Weight Watchers and Zone, use a combination of methods to achieve their goals. As a consequence, what happened? Participants who adhered to the diet lost weight regardless of which one they chose; those who did not did not lose even a single pound.
The conclusion is that all diets are effective as long as they are in compliance with the laws of physics. Mark Haub, a professor of human nutrition at Kansas State University, has some words of wisdom. Haub was fed up with the pseudoscientific hoopla that surrounded so many diets, so he created his own diet that was comprised only of junk food. For 10 weeks, he ate nothing but sweets, cereal, chips, and cookies, with the exception of water. The most important thing to note is that he never ingested more than 1,800 calories in a single day. He had dropped 27 pounds after two and a half months of hard work. Now, no one, even Haub, is pushing for this kind of diet, since it is obviously harmful to one's health. However, it is worthwhile to consider his argument the next time you come across someone who is promoting the newest miracle diet. But, in general, the concept remains the same: if you can burn calories, you will be able to lose pounds.
The conclusion of the novel Burn.
The most important lesson in these notes is that human existence is dependent on the billions of cells that make up our body. Energy is required for the job that these cells perform, which includes the production of enzymes, neurotransmitters, and DNA. We get energy from calories, and metabolism is the measurement of how much energy we “burn.” It is safe to say that our metabolism has stayed mostly unchanged since the Paleolithic era. We all burn approximately the same amount of calories, whether we're sedentary urbanites or energetic hunter-gatherers, since we're all doing the same thing. What is the conclusion? If physical activity does not result in increased calorie expenditure, obesity must be a result of gluttony rather than laziness.
Buy book - Burn by Herman Pontzer
Written by BrookPad Team based on Burn by Herman Pontzer