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5 days ago
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What causes obesity? A major new study is upending common wisdom.
Obesity is uncommon among Hadza hunter-gatherers in Tanzania, Tsimane forager-farmers in Bolivia, Tuvan herder-farmers in Siberia, and other people in less-developed nations. But it's widespread among those of us in wealthy, highly industrialized nations. Why? A major study published this week in PNAS brings surprising clarity to that question. Using objective data about metabolic rates and energy expenditure among more than 4,000 men and women living in dozens of nations across a broad spectrum of socioeconomic conditions, the study quantified how many calories people from different cultures burn most days. Subscribe to The Post Most newsletter for the most important and interesting stories from The Washington Post. For decades, common wisdom and public health messaging have assumed that people in highly developed nations, like the United States, are relatively sedentary and burn far fewer daily calories than people in less-industrialized countries, greatly increasing the risk for obesity. But the new study says no. Instead, it finds that Americans, Europeans and people living in other developed nations expend about the same number of total calories most days as hunter-gatherers, herders, subsistence farmers, foragers and anyone else living in less-industrialized nations. That unexpected finding almost certainly means inactivity is not the main cause of obesity in the U.S. and elsewhere, said Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University in North Carolina and a senior author of the new study. What is, then? The study offers provocative hints about the role of diet and some of the specific foods we eat, as well as about the limits of exercise, and the best ways, in the long run, to avoid and treat obesity. - - - Is diet or inactivity causing obesity? 'There's still a lively debate in public health about the role of diet and activity' in the development of obesity, Pontzer said, especially in wealthy nations. Some experts believe we're exercising too little, others that we're eating too much, and still more that the two contribute almost equally. Understanding the relative contributions of diet and physical activity is important, Pontzer noted, because we can't effectively help people with obesity unless we first tease out its origins. But few large-scale studies have carefully compared energy expenditure among populations prone to obesity against those more resistant to it, which would be a first step toward figuring out what drives weight gain. So, for the new study, Pontzer and his 80-plus co-authors gathered existing data from labs around the world that use doubly labeled water in metabolism studies. Doubly labeled water contains isotopes that, when excreted in urine or other fluids, allow researchers to precisely determine someone's energy expenditure, metabolic rates and body-fat percentage. It's the gold standard in this kind of research. They wound up with data for 4,213 men and women from 34 countries or cultural groups, running the socioeconomic gamut from tribes in Africa to executives in Norway. They calculated total daily energy expenditures for everyone, along with their basal energy expenditure, which is the number of calories our bodies burn during basic, biological operations, and physical activity energy expenditure, which is how many calories we use while moving around. - - - A new theory of how our metabolisms work After adjusting for body size (since people in wealthy nations tend to have larger bodies, and larger bodies burn more calories), they started comparing different groups. Anyone expecting a wide range of energy expenditures, with hunter-gatherers and farmer-herders at the high end and deskbound American office workers trailing well behind, would be wrong. Across the board, the total daily energy expenditures of the 4,213 people were quite similar, no matter where they lived or how they spent their lives. Although the hunter-gatherers and other similar groups moved around far more throughout the day than a typical American, their overall daily calorie burns were nearly the same. The findings, though counterintuitive, align with a new theory about our metabolisms, first proposed by Pontzer. Known as the constrained total energy expenditure model, it says that our brains and bodies closely monitor our total energy expenditure, keeping it within a narrow range. If we start consistently burning extra calories by, for instance, stalking prey on foot for days or training for a marathon, our brains slow down or shut off some tangential biological operations, often related to growth, and our overall daily calorie burn stays within a consistent band. - - - The role of ultra-processed foods The upshot is that 'there is no effect of economic development on size-adjusted physical activity expenditure,' Pontzer says. In which case, the fundamental problem isn't that we're moving too little, meaning more exercise is unlikely to reduce obesity much. What could, then? 'Our analyses suggest that increased energy intake has been roughly 10 times more important than declining total energy expenditure in driving the modern obesity crisis,' the study authors write. In other words, we're eating too much. We may also be eating the wrong kinds of foods, the study also suggests. In a sub-analysis of the diets of some of the groups from both highly and less-developed nations, the scientists found a strong correlation between the percentage of daily diets that consists of 'ultra-processed foods' - which the study's authors define as 'industrial formulations of five or more ingredients' - and higher body-fat percentages. We are, to be blunt, eating too much and probably eating too much of the wrong foods. 'This study confirms what I've been saying, which is that diet is the key culprit in our current [obesity] epidemic,' said Barry Popkin, a professor at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill and an obesity expert. 'This is a well-done study,' he added. Other experts agree. 'It's clear from this important new research and other studies that changes to our food, not our activity, are the dominant drivers of obesity,' said Dariush Mozaffarian, director of the Food is Medicine Institute at Tufts University in Boston. The findings don't mean, though, that exercise is unimportant, Pontzer emphasized. 'We know that exercise is essential for health. This study doesn't change that,' he said. But the study does suggest that 'to address obesity, public health efforts need to focus on diet,' he said, especially on ultra-processed foods, 'that seem to be really potent causes of obesity.' Related Content He may have stopped Trump's would-be assassin. Now he's telling his story. He seeded clouds over Texas. Then came the conspiracy theories. How conservatives beat back a Republican sell-off of public lands
Yahoo
5 days ago
- Health
- Yahoo
What causes obesity? A major new study is upending common wisdom.
Obesity is uncommon among Hadza hunter-gatherers in Tanzania, Tsimane forager-farmers in Bolivia, Tuvan herder-farmers in Siberia, and other people in less-developed nations. But it's widespread among those of us in wealthy, highly industrialized nations. Why? A major study published this week in PNAS brings surprising clarity to that question. Using objective data about metabolic rates and energy expenditure among more than 4,000 men and women living in dozens of nations across a broad spectrum of socioeconomic conditions, the study quantified how many calories people from different cultures burn most days. Subscribe to The Post Most newsletter for the most important and interesting stories from The Washington Post. For decades, common wisdom and public health messaging have assumed that people in highly developed nations, like the United States, are relatively sedentary and burn far fewer daily calories than people in less-industrialized countries, greatly increasing the risk for obesity. But the new study says no. Instead, it finds that Americans, Europeans and people living in other developed nations expend about the same number of total calories most days as hunter-gatherers, herders, subsistence farmers, foragers and anyone else living in less-industrialized nations. That unexpected finding almost certainly means inactivity is not the main cause of obesity in the U.S. and elsewhere, said Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University in North Carolina and a senior author of the new study. What is, then? The study offers provocative hints about the role of diet and some of the specific foods we eat, as well as about the limits of exercise, and the best ways, in the long run, to avoid and treat obesity. - - - Is diet or inactivity causing obesity? 'There's still a lively debate in public health about the role of diet and activity' in the development of obesity, Pontzer said, especially in wealthy nations. Some experts believe we're exercising too little, others that we're eating too much, and still more that the two contribute almost equally. Understanding the relative contributions of diet and physical activity is important, Pontzer noted, because we can't effectively help people with obesity unless we first tease out its origins. But few large-scale studies have carefully compared energy expenditure among populations prone to obesity against those more resistant to it, which would be a first step toward figuring out what drives weight gain. So, for the new study, Pontzer and his 80-plus co-authors gathered existing data from labs around the world that use doubly labeled water in metabolism studies. Doubly labeled water contains isotopes that, when excreted in urine or other fluids, allow researchers to precisely determine someone's energy expenditure, metabolic rates and body-fat percentage. It's the gold standard in this kind of research. They wound up with data for 4,213 men and women from 34 countries or cultural groups, running the socioeconomic gamut from tribes in Africa to executives in Norway. They calculated total daily energy expenditures for everyone, along with their basal energy expenditure, which is the number of calories our bodies burn during basic, biological operations, and physical activity energy expenditure, which is how many calories we use while moving around. - - - A new theory of how our metabolisms work After adjusting for body size (since people in wealthy nations tend to have larger bodies, and larger bodies burn more calories), they started comparing different groups. Anyone expecting a wide range of energy expenditures, with hunter-gatherers and farmer-herders at the high end and deskbound American office workers trailing well behind, would be wrong. Across the board, the total daily energy expenditures of the 4,213 people were quite similar, no matter where they lived or how they spent their lives. Although the hunter-gatherers and other similar groups moved around far more throughout the day than a typical American, their overall daily calorie burns were nearly the same. The findings, though counterintuitive, align with a new theory about our metabolisms, first proposed by Pontzer. Known as the constrained total energy expenditure model, it says that our brains and bodies closely monitor our total energy expenditure, keeping it within a narrow range. If we start consistently burning extra calories by, for instance, stalking prey on foot for days or training for a marathon, our brains slow down or shut off some tangential biological operations, often related to growth, and our overall daily calorie burn stays within a consistent band. - - - The role of ultra-processed foods The upshot is that 'there is no effect of economic development on size-adjusted physical activity expenditure,' Pontzer says. In which case, the fundamental problem isn't that we're moving too little, meaning more exercise is unlikely to reduce obesity much. What could, then? 'Our analyses suggest that increased energy intake has been roughly 10 times more important than declining total energy expenditure in driving the modern obesity crisis,' the study authors write. In other words, we're eating too much. We may also be eating the wrong kinds of foods, the study also suggests. In a sub-analysis of the diets of some of the groups from both highly and less-developed nations, the scientists found a strong correlation between the percentage of daily diets that consists of 'ultra-processed foods' - which the study's authors define as 'industrial formulations of five or more ingredients' - and higher body-fat percentages. We are, to be blunt, eating too much and probably eating too much of the wrong foods. 'This study confirms what I've been saying, which is that diet is the key culprit in our current [obesity] epidemic,' said Barry Popkin, a professor at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill and an obesity expert. 'This is a well-done study,' he added. Other experts agree. 'It's clear from this important new research and other studies that changes to our food, not our activity, are the dominant drivers of obesity,' said Dariush Mozaffarian, director of the Food is Medicine Institute at Tufts University in Boston. The findings don't mean, though, that exercise is unimportant, Pontzer emphasized. 'We know that exercise is essential for health. This study doesn't change that,' he said. But the study does suggest that 'to address obesity, public health efforts need to focus on diet,' he said, especially on ultra-processed foods, 'that seem to be really potent causes of obesity.' Related Content He may have stopped Trump's would-be assassin. Now he's telling his story. He seeded clouds over Texas. Then came the conspiracy theories. How conservatives beat back a Republican sell-off of public lands
Yahoo
6 days ago
- Health
- Yahoo
What causes obesity? A major new study is upending common wisdom.
Obesity is uncommon among Hadza hunter-gatherers in Tanzania, Tsimane forager-farmers in Bolivia, Tuvan herder-farmers in Siberia, and other people in less-developed nations. But it's widespread among those of us in wealthy, highly industrialized nations. Why? A major study published this week in PNAS brings surprising clarity to that question. Using objective data about metabolic rates and energy expenditure among more than 4,000 men and women living in dozens of nations across a broad spectrum of socioeconomic conditions, the study quantified how many calories people from different cultures burn most days. Subscribe to The Post Most newsletter for the most important and interesting stories from The Washington Post. For decades, common wisdom and public health messaging have assumed that people in highly developed nations, like the United States, are relatively sedentary and burn far fewer daily calories than people in less-industrialized countries, greatly increasing the risk for obesity. But the new study says no. Instead, it finds that Americans, Europeans and people living in other developed nations expend about the same number of total calories most days as hunter-gatherers, herders, subsistence farmers, foragers and anyone else living in less-industrialized nations. That unexpected finding almost certainly means inactivity is not the main cause of obesity in the U.S. and elsewhere, said Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University in North Carolina and a senior author of the new study. What is, then? The study offers provocative hints about the role of diet and some of the specific foods we eat, as well as about the limits of exercise, and the best ways, in the long run, to avoid and treat obesity. - - - Is diet or inactivity causing obesity? 'There's still a lively debate in public health about the role of diet and activity' in the development of obesity, Pontzer said, especially in wealthy nations. Some experts believe we're exercising too little, others that we're eating too much, and still more that the two contribute almost equally. Understanding the relative contributions of diet and physical activity is important, Pontzer noted, because we can't effectively help people with obesity unless we first tease out its origins. But few large-scale studies have carefully compared energy expenditure among populations prone to obesity against those more resistant to it, which would be a first step toward figuring out what drives weight gain. So, for the new study, Pontzer and his 80-plus co-authors gathered existing data from labs around the world that use doubly labeled water in metabolism studies. Doubly labeled water contains isotopes that, when excreted in urine or other fluids, allow researchers to precisely determine someone's energy expenditure, metabolic rates and body-fat percentage. It's the gold standard in this kind of research. They wound up with data for 4,213 men and women from 34 countries or cultural groups, running the socioeconomic gamut from tribes in Africa to executives in Norway. They calculated total daily energy expenditures for everyone, along with their basal energy expenditure, which is the number of calories our bodies burn during basic, biological operations, and physical activity energy expenditure, which is how many calories we use while moving around. - - - A new theory of how our metabolisms work After adjusting for body size (since people in wealthy nations tend to have larger bodies, and larger bodies burn more calories), they started comparing different groups. Anyone expecting a wide range of energy expenditures, with hunter-gatherers and farmer-herders at the high end and deskbound American office workers trailing well behind, would be wrong. Across the board, the total daily energy expenditures of the 4,213 people were quite similar, no matter where they lived or how they spent their lives. Although the hunter-gatherers and other similar groups moved around far more throughout the day than a typical American, their overall daily calorie burns were nearly the same. The findings, though counterintuitive, align with a new theory about our metabolisms, first proposed by Pontzer. Known as the constrained total energy expenditure model, it says that our brains and bodies closely monitor our total energy expenditure, keeping it within a narrow range. If we start consistently burning extra calories by, for instance, stalking prey on foot for days or training for a marathon, our brains slow down or shut off some tangential biological operations, often related to growth, and our overall daily calorie burn stays within a consistent band. - - - The role of ultra-processed foods The upshot is that 'there is no effect of economic development on size-adjusted physical activity expenditure,' Pontzer says. In which case, the fundamental problem isn't that we're moving too little, meaning more exercise is unlikely to reduce obesity much. What could, then? 'Our analyses suggest that increased energy intake has been roughly 10 times more important than declining total energy expenditure in driving the modern obesity crisis,' the study authors write. In other words, we're eating too much. We may also be eating the wrong kinds of foods, the study also suggests. In a sub-analysis of the diets of some of the groups from both highly and less-developed nations, the scientists found a strong correlation between the percentage of daily diets that consists of 'ultra-processed foods' - which the study's authors define as 'industrial formulations of five or more ingredients' - and higher body-fat percentages. We are, to be blunt, eating too much and probably eating too much of the wrong foods. 'This study confirms what I've been saying, which is that diet is the key culprit in our current [obesity] epidemic,' said Barry Popkin, a professor at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill and an obesity expert. 'This is a well-done study,' he added. Other experts agree. 'It's clear from this important new research and other studies that changes to our food, not our activity, are the dominant drivers of obesity,' said Dariush Mozaffarian, director of the Food is Medicine Institute at Tufts University in Boston. The findings don't mean, though, that exercise is unimportant, Pontzer emphasized. 'We know that exercise is essential for health. This study doesn't change that,' he said. But the study does suggest that 'to address obesity, public health efforts need to focus on diet,' he said, especially on ultra-processed foods, 'that seem to be really potent causes of obesity.' Related Content He may have stopped Trump's would-be assassin. Now he's telling his story. He seeded clouds over Texas. Then came the conspiracy theories. How conservatives beat back a Republican sell-off of public lands
Washington Post
6 days ago
- Health
- Washington Post
What causes obesity? A major new study is upending common wisdom.
Obesity is uncommon among Hadza hunter-gatherers in Tanzania, Tsimane forager-farmers in Bolivia, Tuvan herder-farmers in Siberia, and other people in less-developed nations. But it's widespread among those of us in wealthy, highly industrialized nations. Why? A major study published this week in PNAS brings surprising clarity to that question. Using objective data about metabolic rates and energy expenditure among more than 4,000 men and women living in dozens of nations across a broad spectrum of socioeconomic conditions, the study quantified how many calories people from different cultures burn most days.
Boston Globe
08-07-2025
- Health
- Boston Globe
A common assumption about aging may be wrong, study suggests
Advertisement Scientists compared inflammation signals in existing data sets from four distinct populations in Italy, Singapore, Bolivia and Malaysia; because they didn't collect the blood samples directly, they couldn't make exact apples-to-apples comparisons. But if validated in larger studies, the findings could suggest that diet, lifestyle and environment influence inflammation more than aging itself, said Alan Cohen, an author of the paper and an associate professor of environmental health sciences at Columbia University. 'Inflammaging may not be a direct product of aging, but rather a response to industrialized conditions,' he said, adding that this was a warning to experts like him that they might be overestimating its pervasiveness globally. 'How we understand inflammation and aging health is based almost entirely on research in high-income countries like the U.S.,' said Thomas McDade, a biological anthropologist at Northwestern University. But a broader look shows that there's much more global variation in aging than scientists previously thought, he added. Advertisement The study 'sparks valuable discussion' but needs much more follow-up 'before we rewrite the inflammaging narrative,' said Bimal Desai, a professor of pharmacology who studies inflammation at the University of Virginia School of Medicine. Inflammation is different in different places In the study, researchers compared blood samples from about 2,800 adults ages 18-95. People in the more industrialized Chianti region of Italy and in Singapore both showed the types of proteins that signal inflammaging. The Tsimane group in Bolivia and the Orang Asli group in Malaysia, on the other hand, had different inflammatory markers likely tied to infections, instead of the proteins marking inflammaging. (The four datasets used blood samples with subjects' informed consent, whether written or verbal, and institutional approval.) The fact that inflammation markers looked so similar in groups from industrialized regions, but so different from the others, is striking, said Aurelia Santoro, an associate professor at the University of Bologna who was not involved in the study. 'This suggests that immune cells are activated in fundamentally different ways depending on context.' The Tsimane population's protein markers were less linked to inflammaging than the Orang Asli's; authors speculated that this might be because of differences in lifestyle and diet. Some experts questioned the findings' significance. Vishwa Deep Dixit, director of the Yale Center for Research on Aging, said it's not surprising that lifestyles with less exposure to pollution are linked to lower rates of chronic disease. 'This becomes a circular argument' that doesn't prove or disprove whether inflammation causes chronic disease, he said. Advertisement Either way, the findings need to be validated in larger, more diverse studies that follow people over time, experts said. While they had lower rates of chronic disease, the two Indigenous populations tended to have life spans shorter than those of people in industrialized regions, meaning they may simply not have lived long enough to develop inflammaging, Santoro said. The problem may be tied to urban living Because the study looked at protein markers in blood samples, and not specific lifestyle or diet differences among populations, scientists had to make educated guesses about why industrialized groups experience more inflammaging, Cohen said. McDade, who has previously studied inflammation in the Tsimane group, speculated that populations in nonindustrialized regions might be exposed to certain microbes in water, food, soil and domestic animals earlier in their lives, bolstering their immune response later in life. At the same time, people in urbanized, industrial environments are 'exposed to a lot of pollutants and toxins,' many of which have 'demonstrated pro-inflammatory effects,' he said. Diet and lifestyle could also play a part: The Tsimane tend to live in small settlements with their extended family and eat a largely plant-based diet, he said. There might also be good and bad types of inflammation, Cohen said. While the Indigenous populations did experience inflammation from infection, those levels weren't tied to chronic disease later in life. That could mean that the presence of inflammation alone isn't as bad as we thought, he added. It's not clear if people can do anything to manage inflammaging late in life. People who want to age more healthily may be better off eating better and exercising more to regulate immune response in the long run, instead of focusing on drugs or supplements advertised to target inflammation, Cohen said. Advertisement This article originally appeared in
