Conventional wisdom dictates that sitting quietly on a couch is about the safest activity possible, but new research suggests that a lifestyle that involves a great deal of such inactivity comes with a number of health risks and could even prove deadly.

An ongoing study conducted by researchers at the University of South Carolina’s Arnold School of Public Health has tracked more than 80,000 people with inactive lifestyles, and since it began in 1970, it has found that fitness level, a proxy for level of activity, was a reliable predictor of early mortality.

Some of the data collected by the team indicates that 40 million to 50 million Americans do not engage in any regular physical activity, putting them at risk of developing life-threatening illnesses such as heart disease or breast cancer.

Researcher Steven Blair sees this as national crisis. "We need numerous changes to promote more physical activity for all, including public policies, changes in the health care system, promoting activity in educational settings and worksites, and social and physical environmental changes," said Blair.

While increasing activity levels is a simple solution, it isn’t always easy to follow through with such a course of action. A good first step might include gradually increasing physical activity over time and boosting energy with dietary supplements such as B vitamins, green tea or ginseng.