Obesity and exercise are on the rise for those living in the United States - a confusing paradox that has researchers calling for more aggressive measures to ensure the overall health of Americans.
Two studies conducted by researchers at the University of Washington's Institute of Health Metrics and Evaluation published this week in the journal Population Health Metrics articulate these two trends clearly.
One, which examined the rise in activity level throughout the nation, used data from the Behavioral Risk Factor Surveillance System (BRFSS), a state-based random-digit telephone survey that covers the majority of the counties in the country.
The researchers calculated body mass index from self-reported weight and height survey answers, adjusting for self-reporting bias using the National Health and Nutrition Examination Study, a nationally representative sample of the U.S. civilian population.
They then calculated self-reported physical activity, ultimately estimating obesity and physical activity prevalence for each county for 2001 to 2011 using validated small area estimation methods.
The results showed that physical activity throughout the nation's counties is increasing, with levels generally higher for men than women and counties in California, Florida, Georgia and Kentucky reporting the largest gains.
This increase, however, was matched by an increase in obesity in almost all the counties during the same time period: all told, for every 1 percentage point increase in physical activity prevalence, obesity prevalence was just 0.11 percentage points lower, controlling for factors such as poverty and baseline levels of obesity.
Meanwhile, according to the second of the two studies, life expectancy is also on the rise in the United States, with women expected to live to 80.9 years in 2010 compared to 78 years in 1985. Men experienced an even higher rise from 75.5 in 1985 to 81.7 in 2010.
However, when compared to other nations, the researchers found this rise to be stunted.
"That's slow progress in life expectancy compared to other countries around the world, and it's especially slow for women," said Dr. Haidong Wang, an assistant professor of global health at IHME and lead author of study on longevity.
Based on these studies, Dr. Christopher Murray, the director of IHME, argues that more must be done to improve the overall health of Americans than exercise alone.
"Around the country, you can see huge increases in the percentage of people becoming physically active, which research tells us is certain to have health benefits," Murray said. "If communities in the U.S. can replicate this success and tackle the ongoing obesity impact, it will see more substantial gains."