If you spend all day sitting down for work — and also while commuting or even relaxing — no doubt you are aware that your sedentary lifestyle is killing you.
But according to a new analysis of studies of this subject, published July 27 in the Lancet, you may actually be able to counteract most or even almost all the negative effects of sitting with enough exercise.
This is both a big deal and surprise. While we've known that exercise has profound effects and can add years to your life, a lot of previous research has shown that even people who meet the US government's recommendations for physical activity can't eliminate the increased risk of early death that's associated with sitting all day.
The catch with the new study is that you have to work out more than most any country's fitness guidelines recommend. The CDC's current fitness guidelines for adults call for at least two and half hours of moderate intensity activity plus at least two muscle-strengthening days a week — a total of about 30 minutes every day. Right now, only 20% of people meet that goal.
But the new review, which included data from 16 studies that followed more than a million people over time, found that people who got at a minimum of 60 to 75 minutes of moderate intensity exercise a day didn't have a significantly increased risk of death compared the baseline group, even if they sat for more than eight hours a day. The baseline group of people sat less than four hours a day and got that minimum of 60 to 75 minutes of exercise.
People who watch more than five hours of television a day also have a dramatically increased risk of early death compared to that baseline group. For people who work out more than an hour a day and yet still watch this much TV, almost all of that increased death risk disappears, but not quite all.
More than an hour of moderately intense exercise each day might sound like a lot, especially for the 80% of people that don't meet current guidelines, but it doesn't take too much to qualify. Brisk walking and moderate cycling count as "moderate intensity exercise."
Why exercise is such a big deal
This analysis can only find associations; it can't tell you cause and effect. People who are especially sedentary have an especially high likelihood of dying sooner because of diabetes, heart disease, or other illnesses. Based on these studies, we know that for people who get a good amount of moderate intensity exercise, that increased risk almost entirely disappears.
After controlling for other possible causes, the researchers think exercise is the reason why.
Other aspects of their data support the idea that exercise is important too. People who don't exercise (less than five minutes a day) but who also sit the least (less than four hours a day) have a much higher risk of death than people in the baseline group.
Digging into the findings
The following two charts help break it down.
This first one breaks down the study populations into four categories based on how much they exercise and then shows people's increased risk of death (y-axis) compared to how much they sit each day. You can read the exercise reference categories from left to right as "at least 60-75 minutes of moderate intensity exercise each day," 50-65 minutes of moderate intensity exercise, 25-35 minutes of moderate intensity exercise, and less than five minutes of exercise a day.
As you can see in the above chart, people who worked out the most had essentially no increased risk of death, while not exercising at all and sitting more than eight hours a day was associated with a more than 50% increase in death risk. The more people exercised, the better.
The following chart compares exercise time to time spent watching TV.
The data here was a little bit more variable, possibly because there was less of it, according to the study. But the general trend still applies. Spending a lot of time watching TV is associated with a higher risk of death. The more you work out, the less increased risk there seems to be. But if you watch more than five hours of television a day, that risk never fully disappears, even if you are among the most active group.
The takeaway? You're in control
The takeaway from this massive review is both a simple and hopeful one. Behavior can make a difference, even if our modern lives are inherently unhealthy, and that's a great thing to hear.
"There has been a lot of concern about the health risks associated with today's more sedentary lifestyles," lead study author Professor Ulf Ekelund, from the Norwegian School of Sports Sciences, Norway and the University of Cambridge, says in a press release. "Our message is a positive one: it is possible to reduce — or even eliminate — these risks if we are active enough, even without having to take up sports or go to the gym."
Just walking or biking does the trick.
Ekelund adds: "For many people who commute to work and have office-based jobs, there is no way to escape sitting for prolonged periods of time. For these people in particular, we cannot stress enough the importance of getting exercise, whether it's getting out for a walk at lunchtime, going for a run in the morning or cycling to work. An hour of physical activity per day is the ideal, but if this is unmanageable, then at least doing some exercise each day can help reduce the risk."
So get moving.
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