Snow may still cover many parts of the U.S., but beach season is right around the corner.
As people work to get toned for summer activities, one scientist warns that human evolution may be why our bodies want to hold on to fat – and that exercise may not impact it the way we expect.
“Our metabolic engines were not crafted by millions of years of evolution to guarantee a beach-ready bikini body,” said Herman Pontzer of Duke University’s Pontzer lab, in his 2021 book “Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy.”
Pontzer, a 44-year-old biological anthropologist, has been studying calories and energy use by primates for decades. His goal is to figure out how humans maintain big brains, lengthy childhoods, many children and long lives through energy consumption, according to the American Association for the Advancement of Science.
So far, Pontzer has found that humans burn more energy per day than other great apes such as chimpanzees, bonobos, gorillas and orangutans.
Human brains take up an estimated 20 percent of our energy use per day.
Compared to other apes, human males pack on twice as much body fat and human females pack on three times as much, said Pontzer. He believes that this fat storage and human metabolism are linked, since fat burns less energy than lean tissue and provides a fuel reserve.
“It gives us more energy every day so we can fuel our big brains as well as feed and protect offspring with long, energetically costly childhoods,” explained the American Association for the Advancement of Science.
Data Pontzer and colleagues collected from systematically measuring the total energy used per day by animals and people also indicates that exercise doesn’t actually help burn more energy on average.
For example, research from Pontzer and Amy Luke at Loyola University Chicago indicates that active hunter-gatherers in Africa – who walk more in one day that the typical American does in one week – don’t expend more energy daily than sedentary office workers in Illinois.
From his research Pontzer hypothesizes that food sharing, a common practice by the Hadza hunter-gatherer people of Africa and, of course, throughout the world by humans, may have helped us stay active and maintain fast metabolisms.
“Instead of increasing the calories burned per day, the Hadza’s physical activity was changing the way they spend their calories,” he explained.
While athletes train and exercise more, their metabolic engines could cut back elsewhere to make room for the extra energy use. For people who are not as active, there is more energy for internal processes such as stress response, Pontzer said.
“His work is revolutionary,” says paleoanthropologist Leslie Aiello, past president of the Wenner-Gren Foundation, which has funded Pontzer’s work. “We now have data … that has given us a completely new framework for how we think about how humans adapted to energetic limits.”
His work may indicate that exercise won’t always lead to weight loss, an idea backed up by other scientists.
“You can’t exercise your way out of obesity,” says evolutionary physiologist John Speakman of the Chinese Academy of Sciences.
“It’s one of those zombie ideas that refuses to die.”
According to the U.K. National Food Strategy, “you can’t outrun a bad diet.”
Yet, although exercise without dieting may not always lead to weight loss, but it can impact where fat is stored on the body and lower risk of diabetes and heart disease, according to exercise physiologist John Thyfault of the University of Kansas Medical Center. People who exercise are less likely to gain weight in the first place, he said.
Pontzer agrees. In Africa, the Hadza people stay active into their 70s and 80s and do not have cases of diabetes or heart disease.
“If exercise is tamping down the stress response, that compensation is a good thing,” he said. “Exercise prevents you from getting sick, but diet is your best tool for weight management.”
Going forward, Pontzer hopes data will reveal the hidden cost of mental stress and immune reactions. His research indicates that stress from a non-physical activity such as a math test can increase calorie burn.
“Until we can show how the levers get pulled to make these adjustments in energy use, people will always be skeptical. It’s on us to do the next generation of experiments,” he said.
Related
Related
