The short answer is maybe. It’s a generally accepted principle that watching excessive amounts of television is an unhealthy way to live and probably indicative of other underlying lifestyle issues.
The longer answer involves the comparison between active and passive television-watching. Passive watching requires little attention on the viewer’s part. It would possibly involve sitting on a sofa for hours on end, probably eating (and increasing the weight-category risk factor), with the TV content centered around fictional/humourous storylines that are probably neither educational nor practical to real life. Active watching, on the other hand, would be an exercise in focused attention, with programmes such as documentaries or video-recorded lectures. In the passive scenario, the brain isn’t exerting much effort to comprehend or apply the information that is simply there. In the active scenario, the brain must exert at least some effort to confirm any old information, and often as a prerequisite to acquire the new information. It wouldn’t be so different from reading a book, or a similar exercise in cognition.