A leading exercise expert has warned that American adults leading a sedentary lifestyle are putting themselves at a greater risk of health problems and even early death.
Steven Blair, PED, from the University of South Carolina's Arnold School of Public Health, called Americans' physical inactivity "the biggest public health problem of the 21st century."
He said that research has shown approximately 25 to 35 percent of American adults are inactive, meaning that they have sedentary jobs, no regular physical activity program, and are generally inactive around the house or yard.
"This amounts to 40 million to 50 million people exposed to the hazard of inactivity," Blair said.
"Given that these individuals are doubling their risk of developing numerous health conditions compared with those who are even moderately active and fit, we're looking at a major public health problem," he added.
Blair's extensive research comes primarily from the Aerobics Center Longitudinal Study, in which he found that fitness level was a significant predictor of mortality.
The ongoing study began in 1970, and included more than 80,000 patients.
It showed that poor fitness level accounted for about 16 percent of all deaths in both men and women.
The percentage was calculated by estimating the number of deaths that could have been avoided if people had spent 30 minutes a day walking.
That percentage was significantly higher than when other risk factors were considered, including obesity, smoking, high cholesterol and diabetes.
The study also found that moderately fit men lived six years longer than unfit men.
The researchers said that women who were very fit were 55 percent less likely to die from breast cancer than women who were not in good shape
He said doing something is better than doing nothing, and doing more is better than doing less, at least up to a point.