Make sitting less and moving more a daily habit for good health
Prolonged sitting has been linked to increased risk of type 2 diabetes, heart disease, stroke, and premature death. I-Min Lee, professor in the Department of Epidemiology at Harvard T.H. Chan School of Public Health, recently shared her thoughts about the dangers of sedentary behavior and how much exercise is needed to offset its harms.
Lee, who is also a professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, has been studying the links between physical activity and health outcomes since she was a graduate student at Harvard Chan School, where she earned an ScD in 1991. She has published highly cited studies quantifying the effects of physical inactivity on chronic disease risk and has explored ways to make physical activity more accessible—including debunking the idea that we need to take 10,000 steps every day. Last year, she offered some suggestions for a 20-minute workout aimed at people who are pressed for time.
Q: How much sitting is too much?
A: It is hard to pin down a single number of hours since there is a dose-response relationship—more sitting is worse than less. The detrimental effects of sedentary behavior (which we technically define as sitting as well as reclining while awake) appears to be more marked after around nine hours a day.
Q: Is getting 150 minutes of moderate-to-vigorous physical activity per week enough to counteract the effects of daily prolonged sitting?
A: Studies have shown that physical activity may be insufficient to completely offset the increased risks of being sedentary. A study of ours using self-reported physical activity in one million persons found that more sitting is bad, as is less physical activity, and combining both makes health outcomes worse. Exercising at guideline levels did not completely ameliorate the harms of sitting for mortality. However, we found that for the most active group—who were getting 60-75 minutes of exercise a day—there was little increased risk from high levels of sitting.
Q: What would you recommend for people whose jobs require them to sit all day?
A: It is important to try to be physically active when you can. Try to take breaks from prolonged sitting. Nowadays, many wearables allow people to prompt a time to get up and move. There is no consensus on how long to sit before a break. We often say every 30 minutes, but that is based on convention rather than data.
Try to find other “automatic” ways to incorporate movement into your life, such as parking farther away and taking the stairs instead of the elevator. Rather than being still, do some activity. Some is better than none, and more is better than some. If you’re moving, you can’t be sitting.
Q: What are your thoughts on standing desks?
A: Standing desks may not be that great because long periods of standing without taking breaks to move can lead to lower back pain and swelling of legs. It may be better to use a treadmill desk, but the the good, sturdy ones are expensive, and some people may not like the motion while reading the screen or find it difficult to type.
Q: Do you have any personal strategies for sitting less and moving more during a busy workday?
A: I’m naturally a fidgety person, so I don’t need to set a timer for myself. I tend to get restless and feel the need to stretch or stand up periodically.
