Energy Balance and Exercise

Science Advances is a journal run by a nonprofit group, which recoups its publication costs from authors. It is peer-reviewed, but authors are allowed to suggest reviewers. Would-be authors have made quite a few complaints about “editorial handling,” or the amount of time it takes to even have their submissions rejected. This may be a negative character trait for a publication to have, or it might just show that the publication has stringent standards.

StudyFinds.org is a site where more colloquial writers interpret and explain the sometimes incomprehensible scientific papers to ordinary people. In this context, Ben Renner wrote about a study that seems to throw a monkey wrench into some theories. For one thing, it implies that we don’t need to worry much about how the children have been getting no exercise in pandemic quarantine conditions. Because a lack of exercise isn’t the problem; poor diet is.

Also, the human immune system faces many challenges when people live out in nature, and it has to work overtime, which burns a lot of calories. Baylor University researchers studied members of tribal groups living in the Amazon region, described as forager-horticulturist children. Renner writes:

[D]espite Shuar children being about 25 percent more physically active, the total number of calories spent every day is indistinguishable from American children. Shuar children also have a 20 percent greater resting energy expenditure, mostly because of higher immune system activity.

But just to illustrate how confusing the entire issue is, here is a quotation from Harvard Health Publishing:

Regular exercise increases the amount of energy you burn while you are exercising. But it also boosts your resting energy expenditure… Because resting energy expenditure accounts for 60% to 75% of the calories you burn each day, any increase in resting energy expenditure is extremely important to your weight-loss effort.

What does Baylor say about its own study? “Constraint and Tradeoffs Regulate Energy Expenditure During Childhood” explains how the received wisdom is that “exercise and other metabolic tasks increase total daily energy expenditure,” which certainly seems to make sense, until it doesn’t. The press release says,

However, that model has been increasingly challenged by studies suggesting that total daily energy expenditure is “constrained” within a relatively narrow human range. Consistently exercise more, spend fewer calories on other metabolic tasks and no extra calories overall.

In other words, the Amazonian children don’t spend more calories but spend them differently. This paper is said to represent the first effort to directly test two opposing models of energy use. It appears to show that it is not a sedentary and germ-free lifestyle making American kids fat, because the forest children who are much more active and whose systems cope with a lot more germs, don’t burn any more calories.

Many people who study the human body suspect that the energy balance paradigm is not the whole story. Calories come in, in the form of food, and they go out, in the form of fuel usage. Apparently, other things happen that are not fully understood. Important to remember is that the study authors do not intend to denigrate the importance of physical activity. Dr. Samuel Urlacher says,

Exercise remains critically important for health and for weight management given its effects on appetite, muscle mass, cardiopulmonary function and many other factors. Our results don’t suggest otherwise. Everyone should meet recommended daily physical activity levels.

Your responses and feedback are welcome!

Source: “Children, Diet, Exercise, Health & Medical, Weight Loss,” StudyFinds.org, 08/25/20
Source: “Exercise and weight loss: the importance of resting energy expenditure,” Health.Harvard.edu, Jan 2015
Source: “Eating Too Much — Not Exercising Too Little…,” Baylor.edu, 12/18/19
Image by geya garcia/CC BY 2.0