CBS News:
The exact mechanisms behind the effect aren't yet clear."There are many important factors we don't understand about sedentary time yet," Young said. She stressed that, "the types of studies available identify trends but don't prove cause and effect."
"We don't have information about how much sedentary behavior is bad for health -- the best advice at this time is to 'sit less and move more,'" she added.
How much more? According to the AHA, people should try to get at least 30 minutes of moderate to vigorous exercise a day to reach the recommended 150 minutes of moderate exercise or 75 minutes of vigorous exercise a week.
Dr. Suzanne Steinbaum is a preventive cardiologist at Lenox Hill Hospital in New York City. She agreed that, based on the evidence, sitting is more than just a "lack of moving."
"The real risk simply comes down to the amount we sit, without there being a true antidote [such as exercise]," Steinbaum said.
Still, society has evolved to encourage sitting, she added.