Last year, I heard a great presentation by Harvard's Steven Gortmaker about television and childhood obesity. The epidemiological (non-experimental) association is unassailable between television time and obesity, and between television time and many behavioral problems. Of course, association is not causation, but a hallmark of the work of Gortmaker and his colleagues is their cleverness in chasing down evidence of a causal relationship. Consider Gortmaker's work on Planet Health, one of the few related random assignment studies that includes a TV reduction intervention. Gortmaker summed up his concerns about television in a column for the Boston Globe last fall.
Even non-experimental epidemiological evidence can be made persuasive if it includes careful thought about the mechanism. In the case of television, there are two plausible causal mechanisms. It appears that TV time displaces active time, and hence reduces calorie expenditure. It also appears that heavy TV watchers consume more calories, which may come from eating habits while watching TV, or perhaps from the effectiveness of television food advertising. Gortmaker thinks this second mechanism is most important, but the two are difficult to disentangle.
This post was prompted by hearing this morning about all the wonderful activities schools and places of worship in my community have planned for "TV-Turnoff Week" next week. The national event is April 25-May 1. Some things about healthy living may seem like a burden or a discipline, but I am sure you will find this one nothing but fun.