A new meta-analysis in the Journal of the American Medical Association tells it like it is: television viewing damages our health.  The paper's title is "Television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality" and its abstract reads:

"Context: Prolonged television (TV) viewing is the most prevalent and pervasive sedentary behavior in industrialized countries and has been associated with morbidity and mortality. However, a systematic and quantitative assessment of published studies is not available. Objective: To perform a meta-analysis of all prospective cohort studies to determine the association between TV viewing and risk of type 2 diabetes, fatal or nonfatal cardiovascular disease, and all-cause mortality. Data Sources and Study Selection: Relevant studies were identified by searches of the MEDLINE database from 1970 to March 2011 and the EMBASE database from 1974 to March 2011 without restrictions and by reviewing reference lists from retrieved articles. Cohort studies that reported relative risk estimates with 95% confidence intervals (CIs) for the associations of interest were included. Data Extraction: Data were extracted independently by each author and summary estimates of association were obtained using a random-effects model. Data Synthesis: Of the 8 studies included, 4 reported results on type 2 diabetes (175,938 individuals; 6428 incident cases during 1.1 million person-years of follow-up), 4 reported on fatal or nonfatal cardiovascular disease (34,253 individuals; 1052 incident cases), and 3 reported on all-cause mortality (26　509 individuals; 1879 deaths during 202　353 person-years of follow-up). The pooled relative risks per 2 hours of TV viewing per day were 1.20 (95% CI, 1.14-1.27) for type 2 diabetes, 1.15 (95% CI, 1.06-1.23) for fatal or nonfatal cardiovascular disease, and 1.13 (95% CI, 1.07-1.18) for all-cause mortality. While the associations between time spent viewing TV and risk of type 2 diabetes and cardiovascular disease were linear, the risk of all-cause mortality appeared to increase with TV viewing duration of greater than 3 hours per day. The estimated absolute risk differences per every 2 hours of TV viewing per day were 176 cases of type 2 diabetes per 100,000 individuals per year, 38 cases of fatal cardiovascular disease per 100,000 individuals per year, and 104 deaths for all-cause mortality per 100,000 individuals per year. Conclusion: Prolonged TV viewing was associated with increased risk of type 2 diabetes, cardiovascular disease, and all-cause mortality."

A commentary in the British Medical Journal states: "Watching too much television was associated with type 2 diabetes, cardiovascular disease, and even death in a meta-analysis of eight large cohort studies. The risk of diabetes and cardiovascular disease went up steadily with increased viewing time in pooled analyses-20% more type 2 diabetes for every extra two hours a day (relative risk 1.20, 95% CI 1.14 to 1.27) and 15% more cardiovascular disease (1.15, 1.06 to 1.23). Both associations survived adjustments for diet and body mass index, and so did a 13% increase in all cause mortality for every extra two hours of television (1.13, 1.07 to 1.18). Although these observations can't establish that watching television threatens your life and health directly, they give a strong hint. The studies were big, prospective, and adjusted for multiple risk factors, say the authors. A link between television and poor health is biologically plausible, and there is already evidence from small trials that cutting down on viewing time can at least improve people's lifestyles. Less television may mean less junk food, more exercise, and a lower body mass index. Bigger trials are needed to find out exactly what happens when adults and children switch off, say the authors. People in developed countries spend between 40% and 50% of their spare time in front of the television. For Americans that's an average of five hours a day."

So if an "average American" watches 5 hours of TV a day, that's 35 hours a week.  A nine to five job, which allows an hour for lunch, is only 35 hours of work per week.  I could do a second job in the time the average American spends in front of the goggle box ... or take up a bunch of new interests, spend so much time with friends, get a life ...