TV is a particularly harmful form of entertainment. There are plenty of studies on the negative correlation between hours of TV watched per week and attention span, short-term memory, and general intelligence. The real cost of TV watching is not the number of hours watched, it's the effect on the other hours of your waking life. For me, the effect is noticeable -- when I cut out TV from my life, the improved mental clarity is quite palpable.

So I've switched to other activities for fun, which may not be as physically healthy, but have less mental cost. Smoking a cigar, a light tipple, and reading books while listening to music in a park don't take that toll on my mental acuity.