Those who watch at least two hours of TV a day increase their risk of early death by 13 percent, according to a recent study. The study also found that for every two hours of TV watched, the risk of diabetes increases by 20 percent over eight years, and heart disease increases by 15 percent over 10 years. In general, Americans log an average of five hours of TV viewing a day. The study, published in the Journal of the American Medical Association, reveals that prolonged TV watching means people are engaging in sedentary behavior for hours a day, and most likely eating unhealthy food while doing so.

The author of the study, Dr. Frank Hu, of the Harvard School of Public Health, told Reuters Health that “cutting back on TV watching is an important way to reduce sedentary behaviors and decrease risk of diabetes and heart disease.” Hu and his team reviewed previous research that examined the link between TV time and diseases such as type 2 diabetes. Their analysis included eight studies that followed more than 200,000 people for an average of 7 to 10 years.

“It’s true that people who watch a lot of TV differ from those who watch less, especially in terms of diet and physical activity levels,” Hu said. People who watch a lot of TV are more likely to eat junk food, he explained, but unhealthy diet and inactivity are also consequences of prolonged TV watching, so they explain some of the effects of the sedentary behavior.