Every hour of television watched per day while being sedentary may increase the risk of dying prematurely, and particularly from cardiovascular disease. David Dunstan, from the Baker IDI Heart and Diabetes Institute (Victoria, Australia) tracked the lifestyle habits of 3,846 men and 4,954 women, ages 25 and older, and found that each hour spent age 25 and in front of the television absent of physical activity resulted in:
an 11% increased risk of death from all causes;
a 9% increased risk of cancer death; and
an 18% increased risk of cardiovascular disease-related death.
Additionally, the team warns that their findings apply to both obese and overweight people as well as people with a healthy weight because prolonged periods of sitting have an unhealthy influence on blood sugar and blood fat levels. Writing that: Television viewing time was associated with increased risk of all-cause and [cardiovascular disease] mortality, the team urges that: In addition to the promotion of exercise, chronic disease prevention strategies could focus on reducing sitting time, particularly prolonged television viewing.
Source: A4M: Couch Potatoes At Increased Risk for Premature Death