By Ken Smith, Director, Mobility Division

27597A recent study by a group of physicians from the Stanford Medical School garnered national attention under headlines that included “Obesity: We’re not Over-eating, We’re Under-Exercisingand “What Makes us Fat? Is it Eating too Much or Moving too Little? By putting the focus on the more controversial diet vs. exercise debate, the stories may have missed a significant point: Americans have adopted truly sedentary lifestyles in shockingly large numbers.

The study, led by gastroenterologist Dr. Uri Ladabaum and published in the August issue of the American Journal of Medicine, was an analysis of data collected under the National Health and Nutrition Survey (NHANES). It reviewed and compared survey results from two windows of time: 1988-1994 and 2009-2010. Three primary responses were considered for each participant: how much exercise they got, how many calories they consumed, and their Body Mass Index (BMI), a measure of obesity. In the twenty years between the two reporting windows, participants on the average reported eating approximately the same number of calories while exercising less and growing more obese. This combination led many to conclude that it was lack of exercise, not diet, that contributes most to obesity. But most experts, including Ladabaum himself, caution that the story is more complex. He was recently quoted in the San Francisco Chronicle as saying “The messages can get confusing when one study comes out saying one thing and another comes out saying another, but if we can look at the big picture and use some common sense, we can acknowledge that both things matter.”

A level deeper in the data, however, was a clearer and more deeply concerning message. Numbers of individuals getting no exercise at all have skyrocketed. In the 1990’s, 11.4% of men and 19.1% of women reported that they got “no leisure time physical activity.” In the 2010 response, these percentages jumped to 47.9% and 51.7%, respectively. Those numbers are remarkable – in only 20 years, the number of truly sedentary individuals tripled to over half of the U.S. population. And while this may or may not directly cause obesity, it is clearly bad for overall health.

Another study, published in the August issue of the Journal of the American College of Cardiology, looked at the association between running and mortality risk for over 55,000 adults over a 15 year period. The study reached a somewhat surprising conclusion. Running the equivalent of even five to ten minutes per day “markedly reduced deaths from all causes and cardiovascular disease.” The authors noted that while running was studied, they believed that it could be replaced by any vigorous activity such as swimming or biking.

The combined story of these two studies is that many more Americans are getting no exercise at all at a time when research is showing that significant health gains occur as people move from doing nothing to doing even a small amount of activity. While this is bad news, there is a possible silver lining. If the most valuable thing we can do is to promote small amounts of activity, this message may not seem so daunting to those struggling to lead a healthier lifestyle. With the emergence of new and less expensive activity measurement devices such as fitness watches, we can personalize the messaging in novel ways. This opens up pathways for new research and innovation to directly and positively impact the lives of millions.

Ladabaum U, Mannalithara A, Myer PA, Singh G, Obesity, Abdominal Obesity, Physical Activity, and Caloric Intake in U.S. Adults: 1988-2010, The American Journal of Medicine (2014), doi: 10.1016/j.amjmed.2014.02.026.

Duck-chul Lee, Russell R. Pate, Carl J. Lavie, Xuemei Sui, Timothy S. Church, Steven N. Blair. Leisure-Time Running Reduces All-Cause and Cardiovascular Mortality Risk. Journal of the American College of Cardiology, 2014; 64 (5): 472 DOI: 10.1016/j.jacc.2014.04.058