Introduction: In the fast-paced era, people are generally anxious about weight and health, especially focusing on calorie values. In the face of these anxieties, most people's first choice is often to resort to the Internet, hoping to find a solution to the problem, and the final conclusion is often to exercise more and burn more calories. In the short term, the advice to exercise is correct, we do consume energy during exercise, especially targeted exercise programs, at least the initial stage of the card burn efficiency will be high. However, the results of scientific research have upended our previous understanding that people with high levels of activity do not burn more calories.
Review the history of human evolution
Discover the truth about diet and exercise
In the winter of 1782, the French chemist Antoine Lavoisier and his mathematician friend Pierre-Simon Laplace put the guinea pig into the world's first calorimeter. They then piled snow between the walls of the calorimeter and compared the rate at which the guinea pig's body heat melted snow with the rate at which it exhaled carbon dioxide, thus discovering metabolic phenomena. Since then, the life force of our growth, reproduction, and movement has been scientifically measured. Since then, human physiologists and evolutionary anthropologists have been counting calories.
Professor Herman Pontzer (Pontzer) at Duke University in the United States is committed to exploring the evolution of humans, studying the physiology of humans and other primates, and understanding how ecology, lifestyle, diet and evolutionary history affect human metabolism and health. To that end, the Pontzer team conducted a global metabolic study that measured the calorie burns of hunter-gatherers in Tanzania, city dwellers on the East Coast of the United States, horticulturists in the Amazon, and top marathon runners in North America, and took tools of metabolic science out of the lab to explore the calorie consumption of human distant relatives chimpanzees, bonobos, gorillas, and orangutans. Pontzer's team's findings upend an understanding of how the body burns calories and how exercise and diet affect metabolism and health.
In 2010, the Pontzer research team published a study entitled "Metabolic adaptation for low energy throughput in orangutans" in Proceedings of the National Academy of Sciences (PNAS) (Figure 1). The study, which took human evolutionary distant relatives, the great apes, as experimental subjects, reflected the effects of differences in life history on metabolism by testing differences in energy expenditure between orangutans, humans, and other mammals.
Figure 1 Research results (Source: PNAS)
In this study, the researchers measured the daily energy expenditure (DEE) of orangutans over a 2-week period using the Doubly Labeled Water (DLW) method to test whether differences in life history between orangutans stemmed from differences in energy intake or distribution. The results show that:
● Although the orangutan exercises a large amount, the DEE value is very low, which is the lowest measured value in mammals other than sloths, and its lower DEE value is caused by lower resting metabolism;
Primates typically have lower growth and reproduction rates compared to other mammals, which may be due in part to reduced energy intake to avoid starvation during periods of food scarcity, rather than being caused by changes in energy distribution;
●Orangutans in captivity and protected areas have an abundant food supply, but still have a metabolic rate similar to that of orangutans in the wild.
Commenting on the findings, Pontzer said: "Orangutans are sloths in the 'ape family', humans have a relatively high DEE, indicating that they may have adapted to relatively high energy intake, and the accelerated metabolic rate in the paleohuman lineage is consistent with the high reproductive rate and high brain volume of humans." ”
In 2012, the Pontzer research team published a study titled "Hunter-Gatherer Energetics and Human Obesity" at PLOS ONE (Figure 2). The study, which took Tanzania's Hadza tribe, the last tribe in Africa that still depends on hunting and gathering, explored which aspects of the Western way of life pose the greatest risk of obesity for humans by comparing modern Western and primitive tribal lifestyles.
Figure 2 Research results (Source: PLOS ONE)
Humans have survived and evolved for thousands of years through hunting and gathering food, and food may be scarce in the process, so it takes a lot of energy to hunt and gather food, so the human body must be good at arranging calorie consumption. The hadza people lived a lifestyle similar to that of our ancestors, hunting and gathering on foot using bows and arrows, small axes and digging sticks, without the need for modern tools or equipment. The daily life of the Hadza people is extremely expensive, and in order to obtain food, women walk an average of 8 kilometers a day, while men walk 14 kilometers, which is more than the average modern human walk in a week. Many people think that hadza people are so active that the body's daily energy consumption must be very high, but this is not the case.
In the study, the researchers collected the urine of the Hadza people by having the subjects drink isotope labeled water with deuterium and carbon-18 that replaced the original hydrogen and oxygen, and analyzed the average daily energy expenditure (TEE). The results found:
● Both men and women, hadza people's TEEs are very close to modern social humans, and a lot of physical activity does not increase the Hadza people's TEE, but as many as the staff of the sedentary office;
●Hadza people are very active and lean, with a body fat percentage at the bottom of the normal health range of the population prescribed in the West;
TEE may be a relatively stable and restricted physiological feature of the human species, which is a genetic product of human evolution and is not affected by our diverse lifestyles.
In response to the study, the research team said: "Our metabolism does not have a lot of room for maneuver in terms of energy expenditure, so doing more exercise without changing the diet will not lead to significant weight loss." ”
Don't be afraid to provoke stakeholders
Pontzer Proposes "Conservation of Energy" for Motion
Pontzer believes that the modern media and commercial propaganda of healthy eating mind and exercise methods, can not fully achieve the commitment to shrink the undesirable waistline, restore health and vitality, and shape the perfect metabolism, and the commonality of its failure lies in the fundamental misunderstanding of the human metabolism itself. The human body is not simply a machine that burns calories, so simple that the owner can easily manipulate them to maintain a slim body and good condition. In fact, the human body is a complex and dynamic metabolic system, a "delicate work" obtained through a long period of evolution. Through nearly 30 years of research, Pontzer found that the body strives to keep the number of calories burned each day within a limited range, regardless of lifestyle, and that the body seems to respond to increased daily exercise by reducing energy consumption for other tasks. Pontzer's remarks infuriated some stakeholders, but he publicly said he was not afraid of challenges and questions.
On June 5, 2019, the Pontzer research team published the findings of the study entitled "Extreme events reveal an alimentary limit on sustained maximal human energy expenditure" at Science Advances (Figure 3). Studies have found that under the condition of continuous, high-intensity energy consumption, the body's metabolic level will decrease and tend to a stable state. The final steady state is only the basal metabolic rate, which is 2.5 times the minimum energy expenditure required to maintain basic life.
Figure 3 Research results (Source: Science Advances)
In the study, the researchers collected the total energy expenditure and basal metabolic rate (BMR) of several participants in the "Trans-U.S." event before, the first and last weeks of the competition, and added data from pregnant women. "Across the United States" claims to be "the longest distance in the world" project. Athletes need to run from California on the Pacific coast to Washington on the Atlantic coast in 140 days, which is equivalent to running a 42.2 km marathon every day and running 6 days a week. The results found:
● In the first week, the overall energy consumption of athletes is relatively high, about 6200 kcal per day; at the end of the schedule, it drops to about 4900 kcal. In this way, in order to maintain long-term stability, the body seems to reduce the level of metabolism;
Human sustained energy expenditure, as measured by the Sustained Metabolic Scope (SusMS), is a function of the duration of energy consumption events. For events lasting more than 0.5 to 250 days, SusMS decreased curvature with event duration and stabilized below 3x BCR;
Regardless of the temperature conditions, the limits of continuous energy consumption of athletes are similar and seem to be unaffected by temperature;
If you look at "pregnancy and breastfeeding" as a long-lasting extreme event, pregnant women consume energy at 2.2 times the rate of basal metabolic rate, which is only a little lower than that of extreme athletes.
Combining all the data, it was found that the human digestive energy supply limit is about 2.5 times BMR. Transcontinental race data suggest that humans can partially lower TEE in long distance races to extend endurance. The food that the human body can digest effectively every day and absorb energy and nutrients are limited, which leads to the limited calories we can use.
On February 17, 2022, Pontzer said in an interview with Science: "The metabolism of the human body is dynamic and adaptive, although the energy consumed by exercise has increased, but the metabolism of other aspects of the body will also slow down accordingly, to 'make room' for the needs of exercise, and finally reach a balance." For example, exercise makes the immune system function healthily and inflammation is reduced because inflammation is a risk factor for cardiovascular disease and a range of other health problems; in the face of stress, people who exercise less stress hormones cortisol and adrenaline secrete, which reduces their risk of stress-related diseases; exercise can even make the secretion of reproductive hormones more reasonable, scientists by comparing the secretion of estrogen and progesterone in women with the secretion of testosterone in men, Adults with exercise habits were found to have lower levels of these three classes of hormones, but this reduction did not appear to impair fertility, but was rather associated with a reduced risk of disease such as prostate, ovarian and breast cancer. Although Hadza people consume about the same number of calories a day as sedentary white-collar workers, they are at lower risk of heart disease and diabetes. Regular exercise keeps the heart healthy, strengthens muscles, and sharpens the mind, and this help becomes more prominent with age (Figure 4) [4]. ”
Figure 4 Science feature story (Source: Science)
As Pontzer puts it, "The 'life-saving mechanism' that we have evolved over millions of years did not exist to keep bikinis on the beach." The idea that "exercise really doesn't lose weight" is really incredible. In the face of scientific research data, we still have to remain in awe, and in the theory of "keeping your mouth shut and opening your legs", it seems that keeping your mouth shut seems to be more important.
Source: Wikimedia Commons, for academic communication only.
Written | essay competition
Typography | Qiao Weijun
End
Resources:
[1] Pontzer H, Raichlen DA, Shumaker RW, et al. Metabolic adaptation for low energy throughput in orangutans. Proc Natl Acad Sci U S A. 2010 Aug 10;107(32):14048-52. doi: 10.1073/pnas.1001031107. Epub 2010 Aug 2. PMID: 20679208; PMCID: PMC2922585.
[2] Pontzer H, Raichlen DA, Wood BM, et al. Hunter-gatherer energetics and human obesity. PLoS One. 2012;7(7):e40503. doi: 10.1371/journal.pone.0040503. Epub 2012 Jul 25. PMID: 22848382; PMCID: PMC3405064.
[3] Thurber C, Dugas LR, Speakman JR, et al. Extreme events reveal an alimentary limit on sustained maximal human energy expenditure. Sci Adv. 2019 Jun 5;5(6):eaaw0341. doi: 10.1126/sciadv.aaw0341. PMID: 31183404; PMCID: PMC6551185.
[4]https://www.science.org/content/article/scientist-busts-myths-about-how-humans-burn-calories-and-why
This article is a biological exploration original, welcome to forward and share. If any other media or website needs to be reprinted, the source of biological exploration must be indicated in front of the main text.