OK, so you work in an office and you spend 8 hours sitting at your desk – plus a couple hours of TV in the evening – but all that gym time makes up for all that sedentary action, right? According to a new study published in the Annals of Internal Medicine: wrong.

Researchers report that the amount of time a person spends sitting each day is associated with a higher risk of heart disease, diabetes, cancer and death. What is more, regular exercise may not be enough to offset this risk. 

“More than one half of an average person’s day is spent being sedentary – sitting, watching television, or working at a computer,” Dr. Alter says. “Our study finds that despite the health-enhancing benefits of physical activity, this alone may not be enough to reduce the risk for disease.”

Currently, public health guidelines suggest that adults should walk at least 30 minutes per day. But Dr. Alter says that “it is not good enough to exercise for 30 minutes a day and be sedentary for 23 and [a] half hours.”

He says that people should aim to decrease their sitting time by 2-3 hours in a 12-hour day, suggesting that standing during the commercial breaks on TV, or working standing up at your desk for a couple of hours a day may be beneficial.

However, Dr. Alter emphasizes that these strategies do not replace daily exercise. Rather, because the “health hazards are accelerated quite markedly” among people who do not exercise, reducing sitting time is most important for this group.

Also, Dr. Alter reminds that none of the studies in the meta-analysis are randomized controlled trials. As such, the authors are only able to report an association between sitting time and increased risk for disease, rather than being able to conclusively state that sitting directly causes disease.