Overeating – Not Lack of Exercise – Could be the Root Cause of Obesity

Eating too much, not exercising less could be the underlying cause of obesity, reveals new research by anthropologists from Baylor University, USA. Their study, conducted on children from the Shuar community who live in the Amazon rainforest, could bring about a paradigm shift in our current understanding of obesity and other metabolic disorders. This could pave the way for effectively tackling these diseases in order to reverse global trends.

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A Word about the Shuar Community

The Shuar community are indigenous people of Ecuador and Peru in South America, consisting of around 50,000 individuals. They belong to the Jivaroan clan, who live in the tropical Amazonian rainforests. They primarily live off the land through hunting, fishing, foraging, and subsistence farming, including small-scale horticulture.

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Study Team

The study, published in Science Advances, was led by Dr. Samuel S. Urlacher, PhD, who is an Assistant Professor of Anthropology at Baylor University, Waco, Texas, USA. He is also the Co-Director of the Shuar Health and Life History Project and has spent more than two years living with the Shuar community in the Amazon.

Dr. Herman Pontzer, PhD, who is an Associate Professor of Evolutionary Anthropology at Duke University’s Trinity College of Arts & Sciences, was a study collaborator and co-author. Other study collaborators were from the University of Oregon, Northern Arizona University, and Loyola University, USA.

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Uniqueness of the Study

Conventional human nutrition models have all along assumed that daily energy expenditure arising from exercising and other metabolic functions have an additive effect, leading to increased burning of the total number of calories each day. However, a new model, based on recent studies that have consistently shown that the original model is faulty, as the daily total energy expenditure of the human body is limited to a very narrow range. The uniqueness of the present study is that it is the first study to actually test these two opposite models of energy expenditure among children living in harsh conditions.

Key Features of the Study

• 44 forager-horticulturist Shuar children aged between 5 to 12 years were included in the study
• Energy expenditure data was collected from the Shuar children and compared to data of children from strong economic countries such as USA and UK
• Energy expenditure was measured by isotope-tracking and respirometry techniques – both Gold Standards
• This is the first study to use these state-of-the-art techniques in children from a subsistence-based population
• The energy expenditure data was coupled to data on growth, nutrition, physical activity, and immunity of the study population

Key Findings of the Study

• Shuar children were 25 percent more physically active than US and UK children
• Shuar children had 20 percent higher resting energy expenditure than US and UK children, due to increased immune activity
• Total calories burned daily by Shuar children was the same as that of US and UK children, despite wide differences in lifestyle and quality of food consumed

Pontzer explains: “These findings advance previous work among adults, showing that energy expenditure is also constrained during childhood.”

Implications of the Study

The study findings imply that energy constraints could be the underlying reason for reduced childhood growth and elevated risk of developing obesity and metabolic diseases such as Type 2 diabetes and hypertension (high blood pressure) during adulthood. Moreover, increased physical and immune activity could limit the amount of energy required for growth, despite the unlimited availability of food.

Future Plans

The research team plans to improve the study design in the following ways:

• Inclusion of children of a wider age range
• Comparison of the data generated with additional study populations
• Collection of longitudinal data on lifestyle and economic status within a single population
• Application of the research findings to improve the health of the Shuar community and other populations across the globe

Concluding Remarks

Urlacher indicates: “Conventional wisdom suggests that an increasingly sedentary and germ-free lifestyle, resulting in low daily energy expenditure, is a primary factor underlying rising rates of obesity in the US and elsewhere.” He adds: “The findings of our study challenge that notion. We demonstrate that Amazonian children with physically active lifestyles and chronic immunological challenges don’t actually burn more calories than much more sedentary children living here in the US.”

“This similarity in energy expenditure suggests that the human body can flexibly balance energy budgets in different contexts,” says Urlacher. “Ultimately, eating too much, not moving too little, may be at the core of long-term weight gain and the global nutrition transition that often begins during childhood.”

He concludes: “The science is exciting, but, ultimately, we hope that our research can help to improve health among the Shuar, in the US and elsewhere.”

Funding Source

The study was funded by the National Science Foundation, Alexandria, Virginia, USA.

Reference:

1. Eating Too Much — Not Exercising Too Little — May Be at Core of Weight Gain, Study of Amazonian Children Finds - (https://www.baylor.edu/mediacommunications/news.php?action=story&story=215728)

Source-Medindia