A new Harvard study finds that Americans have forgotten the value of being physically active. Compared to 200 years ago, the average American gets about 30 minutes less exercise today. Despite all the technological advancements in workout equipment, perhaps it’s the technology itself driving sedentary lifestyles.
Between YouTube workout routines, gym memberships, home workout machines, and more, Americans have endless options for exercise. Yet, it seems we’re less physically active than ever, according to researchers from the lab of evolutionary biologist Daniel E. Lieberman.
The research found that body temperatures and metabolic rates of Americans have been falling since the Industrial Revolution. This downshift occurred alongside declining physical activity levels, suggesting sedentary lifestyles have caused these widespread physiological changes. The results of the study have been published in Current Biology.
The researchers discovered that since 1820, Americans had experienced a 6% decline in resting metabolic rate (total number of calories burned at rest). This decrease equates to about 27 minutes less moderate to vigorous physical activity per day than 200 years ago. Authors attribute Americans’ less physically active lifestyle to the widespread use of technology.
“Instead of walking to work, we take cars or trains; instead of manual labor in factories, we use machines,” said Andrew K. Yegian, the study’s lead author and a postdoctoral fellow in the Department of Human and Evolutionary Biology. “We’ve made technology to do our physical activity for us….Our hope is that this helps people think more about the long-term changes of activity that have come with our changes in lifestyle and technology.”
Scientists have observed for decades how Americans have become less physically active with the advent of technology. However, until now, they didn’t have exact data to quantify this drastic societal change.
The paper provides calculations to show that Americans have, in fact, become lazier over time. The research indicates that historical records on resting body temperature act as a thermometer of Americans’ physical activity.
“This is a first pass estimate of taking physiological data and trying to quantify declines in activity,” Yegian said. “The next step would be to try to apply this as a tool to other populations.”
The work began as a rough calculation following the release of new research by Stanford University last year. The study showed that Americans’ average body temperature decreased from 98.6 to about 97.5 degrees Fahrenheit since the 1800s. The authors of this study came to the same conclusion: that slower metabolisms have caused falling body temperatures in the United States.
They cite a few reasons for the decreased metabolism, namely lower inflammation due to improved healthcare and climate-controlled environments. In the 19th century, homes had no central air conditioning and unreliable heating. Today, most people have access to heat and AC, reducing the energy expended to regulate our body temperatures.
Regarding overall health, improvements have occurred despite the negative impacts of our tech-intensive world. It’s undeniable that we have access to better medical treatment, hygiene, and food than people 200 years ago. These societal advancements have lowered our inflammation levels, perhaps due to increased comforts and fewer worries about survival. Lower inflammation leads to reduced body temperature and metabolism, researchers say.
“Physiologically, we’re just different from what we were in the past,” said Julie Parsonnet, MD, lead author of the study. “The environment that we’re living in has changed, including the temperature in our homes, our contact with microorganisms, and the food that we have access to. All these things mean that although we think of human beings as if we’re monomorphic and have been the same for all of human evolution, we’re not the same. We’re actually changing physiologically.”
Better Living Standards Led Us to More Sedentary Lifestyles
Harvard researchers believed that Americans being less physically active correlated with falling body temperatures. The human metabolism, which produces body heat and powers physical activity, may explain these physiological changes.
Scientists analyzed previous studies by other researchers to find more evidence about this theory. They wanted to know how changes in body temperature could affect metabolism and activity levels. So, they gathered data from two papers to quantify how the two were related. Then, they used this data to estimate decreases in physical activity since the 19th century.
The researchers noted that other factors besides being less physically active might affect metabolism and body temperature in the paper. This makes estimating physical activity levels a bit more complicated.
What’s Next for Gaining More Clarity on Why People Are Now Less Physically Active
Their future work would better understand the relationships between metabolism, body temperature, and physical activity. Hopefully, this knowledge will provide more insight into how being less physically active affected the health and morbidity of Americans in the industrial age.
“Physical activity is a major determinant of health,” said Lieberman, the Edwin M. Lerner II Professor of Biological Science. “Understanding how much less active Americans have become over the last few generations can help us assess just how much increases in the incidence of chronic conditions like type 2 diabetes, heart disease, and Alzheimer’s can be attributed to decreases in physical activity.”
It seems that in modern society, we can’t have our cake and eat it too. Sitting too much can lead to many health problems, but life doesn’t require much movement today. In our artificial environment, we’ve figured out how to beat nature. However, our quest to conquer the elements has unleashed a new beast: diseases of modernity.
Thirty minutes may not sound like much, but the effects of being less physically active are apparent everywhere you look. Obesity, heart disease, cancer, diabetes, and other diseases have skyrocketed since the Industrial Revolution. We’ve made advancements in modern medicine and eradicated the most deadly plagues and pandemics. However, in place of those, we now have chronic illnesses primarily caused by everyday life.
A recent Harvard study found that Americans’ resting body temperatures and metabolisms have decreased. This reduction co-occurred with being less physically active, proving that we’ve changed physiologically over time. The impact of these changes isn’t yet clear, however.