Hunter-Gatherer Study Suggests Obesity Epidemic Is Caused by Overeating not Decreased Physical Activity

by Dr Sam Girgis on July 26, 2012

The world is witnessing an obesity epidemic that originated in Western societies, but has now spread to other parts of the world that have adopted the Western diet.  If current worldwide trends continue, within a few years one in three people will be overweight and one in ten will be obese, based upon body mass index measurements.  In the United States, two thirds of the population is already overweight.  Obesity has many known health hazards which include type 2 diabetes, high blood pressure, cardiovascular disease, and some forms of cancer.  If the current trends continue, the obesity epidemic will likely contribute to the growing healthcare costs of the world.  Preventative medicine should be our goal, and slowing and reversing our obesity problem should be a priority.  Traditional theories have suggested that modern lifestyles have contributed to the obesity epidemic due to decreased energy expenditure.  This is thought to occur from our sedentary lifestyles and ease of transportation via automobiles.

Researchers, lead by Dr. Herman Pontzer of Hunter College in New York City, have found that the daily energy expenditure of a modern day hunter-gatherer people is equivalent to that of Western office working people.  This contradicts the theory that the obesity epidemic is driven by our sedentary lifestyle and instead suggests that it is driven by overeating.  The results of their study were published online in the journal PLoS ONE.  The researchers studied the Hadza hunter-gatherer society of northern Tanzania, which is a society that used bows, axes, and digging sticks to forage and hunt for their daily food requirements.  They are the closest modern example of how our hunter-gatherer ancestors may have lived, and provide a good example of how much energy it may have required to live the hunter-gatherer lifestyle.  The investigators found that the daily energy expenditure of the Hadza people was equivalent to those of office working people in the United States and Europe.  This finding remained even after accounting for body weight, body fat percentage, age, and gender.

The authors wrote, “Measurements of [total daily energy expenditure] among Hadza hunter-gatherers challenge the view that Western lifestyles result in abnormally low energy expenditure, and that decreased energy expenditure is a primary cause of obesity in developed countries… Our results indicate that active, ‘‘traditional’’ lifestyles may not protect against obesity if diets change to promote increased caloric consumption. Thus, efforts to supplement diets of healthy populations in developing regions must avoid inundating these individuals with highly-processed, energy-dense but nutrient-poor foods. Since energy throughput in these populations is unlikely to burn the extra calories provided, such efforts may unintentionally increase the incidence of excess adiposity and associated metabolic complications such as insulin resistance. Indeed, processed, energy-dense foods have been linked to insulin resistance and cardiovascular disease among Australian foragers transitioning to village life”.

This study provides evidence that increased caloric intake and overeating is the root cause of the burgeoning worldwide obesity epidemic.  The Western diet is high in calories, contains energy dense foods, and is nutrient poor.  It is also highly processed and sugar rich.  Increased consumption of these types of foods, which ironically have been termed “comfort foods”, is creating a mismatch between energy intake and energy expenditure and fueling the growing obesity epidemic.  Physical activity is beneficial and needed to promote vigor and health.  As this study suggests, the daily energy expenditure of Westerners is not the problem and increased physical activity will likely not solve the obesity epidemic.  In order to reverse the current obesity trend, we will need to consume less food.  This will be increasingly difficult as the food industry strives to make more profit by promoting a “super-sized” diet at the expense of the world’s health.



Herman Pontzer et al. “Hunter-Gatherer Energetics and Human Obesity” 2012 PLoS ONE 7(7): e40503. doi:10.1371/journal.pone.0040503


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