https://www.sciencedaily.com/releas...91218153543.htm
https://advances.sciencemag.org/content/5/12/eaax1065
Okay--I included a sciencedaily link because that's where I got to the study itself from. But I found the article goofy and less succint than the abstract, so that's what I'm copy/pasting here....
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Abstract
Children’s metabolic energy expenditure is central to evolutionary and epidemiological frameworks for understanding variation in human phenotype and health. Nonetheless, the impact of a physically active lifestyle and heavy burden of infectious disease on child metabolism remains unclear. Using energetic, activity, and biomarker measures, we show that Shuar forager-horticulturalist children of Amazonian Ecuador are ~25% more physically active and, in association with immune activity, have ~20% greater resting energy expenditure than children from industrial populations. Despite these differences, Shuar children’s total daily energy expenditure, measured using doubly labeled water, is indistinguishable from industrialized counterparts. Trade-offs in energy allocation between competing physiological tasks, within a constrained energy budget, appear to shape childhood phenotypic variation (e.g., patterns of growth). These trade-offs may contribute to the lifetime obesity and metabolic health disparities that emerge during rapid economic development.
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Increased metabolic rate due to increased immune activity is interesting--obvious implications/avenues to look at when it comes to the gut biome, immune activity and energy expenditure. If you wander around looking at leptin studies, a bit of reference jumping gets you to interactions with the immune system fairly quickly.
The physical activity bit is interesting as well. Assuming that first bit was interesting.
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Physical activity. We estimated the energy cost of physical activity using the ratio of AEE to accelerometer-measured body movement among the Shuar sample. This approach assumes that AEE among the Shuar is entirely (or almost entirely) reflective of musculoskeletal activity, whereas AEE for the U.S./U.K. cohort is inflated by greater diurnal fluctuation in REE. For Shuar children, the ratio of AEE/mean accelerometer counts per minute (CPM; Table 1) yields 0.58 kcal/CPM. Mean body mass in the U.S./U.K. sample is 14% greater than the Shuar sample (Table 1), indicating that that the cost of movement for U.S./U.K. children should be 14% greater or 0.66 kcal/CPM. Last, we assumed that the efficiency of movement might be up to 5% greater for the Shuar due to their greater habitual physical activity (24), which yields a final U.S./U.K. cost of movement of 0.70 kcal/CPM. Multiplying this ratio by observed mean CPM for the industrial sample (379 CPM) yields a cost of physical activity of 264 kcal/day for the industrial TEE model.
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Wall of text--Shuar children have total energy expenditure comparable to the more industrialized children they're compared to here. But resting energy expenditure is higher, and they're also more physically active. T Nation has a lot of articles suggesting mixing up endurance exercise--as we get better at an exercise, we do it more efficiently--burn less calories. Stay inept to burn more calories. So Shuar children are more efficient, and have less mass to move about--so they burn less calories when active.
What I didn't like about the sciencedaily article. The summary wasn't so bad;
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Forager-horticulturalist children in the Amazon rainforest do not spend more calories in their everyday lives than children in the United States, but they do spend calories differently. That finding provides clues for understanding and reversing global trends in obesity and poor metabolic health, according to a new study.
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Leaves room for subtleties. There might be something about
how they spend their calories, about the metabolic activity going on, that contributes to their different, less fat phenotype. Or you could just read the headline;
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Eating too much -- not exercising too little -- may be at core of weight gain
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And here;
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A key takeaway of the study is that rapid change in diet and increasing energy intake, not decreasing physical activity or infectious disease burden, may most directly underlie the chronic weight gain driving the global rise of obesity. However, "Exercise remains critically important for health and for weight management given its effects on appetite, muscle mass, cardiopulmonary function and many other factors," Urlacher said. "Our results don't suggest otherwise. Everyone should meet recommended daily physical activity levels."
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Better than the headline--but still. Immune system burned more calories? Why didn't the children just have larger appetites, and eat to make up for it? Or were they hungry all the time, and not eating to appetite? Saying, well, resting energy expenditure goes down in industrialized children--but it's made up for by increased physical exercise energy expenditure in the face of reduced activity--well, I don't know. Couldn't you as easily say that the children eat more, but that's made up for by increases in energy expenditure during activity--and instead ascribe the increased body weight to the decrease in basal metabolism? Or stated another way--maybe US children eat more, but if it weren't for the decrease in metabolic rate, at least relative to the Shuar children, this wouldn't be causing obesity.
After all this, I do think it's likely the food.
But sheer available calories is a vast oversimplification.
Hunter/gatherer/farmer children bmr
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