The calorie counter (Herman Pontzer 2022)


Senior Member

This is an interesting look into using isotope water to measure energy expenditure and the rather surprising finding that very active people don't often use more energy than sedantry ones over the longer term, not physically moving can reserve energy for internal processes. Stress can also substantially increase short term energy consumption by about 40%. Interesting article. Any one done one of these TEE tests?

Some interesting quotes around the method and some findings, its a long article:

By borrowing a method developed by physiologists studying obesity, Pontzer and colleagues systematically measure the total energy used per day by animals and people in various walks of life. The answers coming from their data are often surprising: Exercise doesn’t help you burn more energy on average; active hunter-gatherers in Africa don’t expend more energy daily than sedentary office workers in Illinois; pregnant women don’t burn more calories per day than other adults, after adjusting for body mass.

Pontzer still measures exhaled CO2 to get at calories burned in a particular activity, as he did with Christina’s stress test. But he found that physiologists had developed a better way to measure TEE over a day: the doubly labeled water method, which measures TEE without asking a subject to breathe into a hood all day.

People drink a harmless cocktail of labeled water, in which distinct isotopes of hydrogen and oxygen replace the common forms. Then researchers sample their urine several times over 1 week. The labeled hydrogen passes through the body into urine, sweat, and other fluids, but as a person burns calories, some of the labeled oxygen is exhaled as CO2. The ratio of labeled oxygen to labeled hydrogen in the urine thus serves as a measure of how much oxygen a person’s cells used on average in a day and therefore how many calories were burned. The method is the gold standard for total energy use, but it costs $600 per test and was out of reach for most evolutionary biologists.

Pontzer got a lesson in the value of food sharing in 2010, when he traveled to Tanzania to study the energy budgets of the Hadza hunter-gatherers. One of the first things he noticed was how often the Hadza used the word “za,” which means “to give.” It’s the magic word all Hadza learn as children to get someone to share berries, honey, or other foods with them. Such sharing helps all the Hadza be active: As they hunt and forage, Hadza women walk about 8 kilometers daily; men, 14 kilometers—more than a typical American walks in 1 week.

To learn about their energy expenditure, Pontzer asked the Hadza whether they’d drink his tasteless water cocktail and give urine samples. They agreed. He almost couldn’t get funding for the study, because other researchers assumed the answer was obvious. “Everyone knew the Hadza had exceptionally high energy expenditures because they were so physically active,” he recalls. “Except they didn’t.”

Individual Hadza had days of more and less activity, and some burned 10% more or less calories than average. But when adjusted for nonfat body mass, Hadza men and women burned the same amount of energy per day on average as men and women in the United States, as well as those in Europe, Russia, and Japan, he reported in PLOS ONE in 2012. “It’s surprising when you consider the differences in physical activity,” Schoeller says.

As the athletes’ ran more and more over weeks or months, their metabolic engines cut back elsewhere to make room for the extra exercise costs, Pontzer says. Conversely, if you’re a couch potato, you might still spend almost as many calories daily, leaving more energy for your body to spend on internal processes such as a stress response.