You head to the gym most days after work and think you’re in pretty good shape. So does that mean you don’t have to worry about the fact that you spend most of the rest of the day sitting?

Absolutely not.

The average person spends more than half of their day sitting, and the average office worker sits for 15 hours a day. All of this sedentary behavior is bad for your health in more ways than you can imagine. And getting in a daily workout doesn’t make up for all the other hours each day you spend at your desk, in your car or on the couch.

Here are 3 reasons you need to sit less:

Sitting is linked to early death. According to a recent study published in the Annals of Internal Medicine, sitting for excessively long periods of time increases your risk of early death by any cause. The study followed nearly 8,000 adults aged 45 and over for an average of four years and found that the more people sat, the higher the risk.

Sitting can lead to weight gain. Sitting burns less calories than other non-exercise related activities, such as standing, strolling or fidgeting. The fewer calories you burn, the more likely you are to gain weight and the harder it is to lose weight.

Sitting may increase your risk of chronic disease. Sedentary behavior has been shown to increase the risk of type 2 diabetes by 112% and up heart disease risk by 147%. Being overweight or obese, a common factor in people who sit for long periods of time, contributes to many chronic conditions such as heart disease, high blood pressure, high cholesterol, insulin resistance, diabetes and some types of cancer.

So what can you do to improve your health?

Exercising each day isn’t enough.

Even if you are committed to a regular exercise routine, this activity doesn’t make up for the negative consequences of prolonged sitting. Numerous studies have found that the health effects of sitting too much occur regardless of how much exercise you participate in.

Get up periodically and move. For every 30 minutes of consecutive sitting, aim to get up and move for 5 minutes. Walk to a coworker’s desk instead of emailing, pace as you talk on the phone, march in place during television commercials or take a walk during your lunch hour. You don’t have to engage in intense physical activity during these short bursts of non-sitting time. Just do something physical that gets you in an upright position and moving.