It may be common sense that activity is good for you and television is bad for you. Parents often tell their children to turn off the tube and play outside in the sun. But when it comes to our health, adults tend to write off their own advice.

After a long day of work, most people would rather relax instead of hitting the gym, which may sound good in the moment. But in the long run, taking that extra effort can add years to your life. And sitting in front of the T.V. can take years away.

The most recent study on this topic, published just last week, indicates that adults who get the recommended 2.5 hours of moderate physical activity each week live an average of 3.4 years longer than those who don’t. Even people who only got in about the half the recommended amount of activity saw a benefit of 1.8 added years. And those who got in double added 4.2 extra years.

The association between activity and added years seemed to be especially strong in people with a family history of cancer or heart disease. Physical activity even helped counter the effects of being overweight or obese, which can take several years off your life. Another recent study also backs up this finding by showing that obese people who stayed fit had fewer negative health conditions than inactive normal-weight people.

However, what about those who choose to be a lump on a log, living a sedentary life of watching T.V. instead of being active? One study of teenagers found that watching television was association with increased weight. This may be due to inactivity or due to snacking while watching. A study from 2003 established that the connection between snacking and television watching could stem from visual cues (commercials, characters eating, etc.) or overeating due to being distracted.

But even more important, this study published just a few months ago found that older adults who watched less television, regardless of how active they were, were less likely to be overweight and obese. And on the other side, while activity usually protects against being overweight or obese, those adults that watched television lost any protective effect they gained from activity.

In addition, the study found that people who got enough exercise but also spent a lot of time sitting around had the same risk of being overweight as people who don’t spend much time sitting or exercising. This means that in order to avoid negative health consequences, you need to reduce the amount of time you sit and watch television, as well as increase the amount of time you spend exercising. You can’t just do one or the other.

So while it may seem exhausting or difficult to get in the recommended amount of physical activity after a long day of work, remember that you’ll be gaining not just days or week but years of life that  you might otherwise have lost.

Speaking of exercise, see what you need to know to get clean air in a gym while working out.

Learn more about getting in quick exercise and eating a balanced diet.