The short answer is yes, for many people. However, this is only one of the issues with excessive tv watching.
Television is a great resource, but watching tv displaces other activities such as homework, creative play, and active play. Most parents trust their children's physical health to their pediatrician. Pediatricians are also informed about media "diets." The American Academy of Pediatrics has specific recommendations (see website) for all ages of children.
Not only do most television programs and channels often include countless ads for unhealthy, highly processed foods, but there has been research supporting the consumption of more calories while viewing television. For example, children in one study ate around 230 more calories while watching television, while in another adults ate an extra 140. While this may not sound like much, the additional caloric intake with little to no energy expenditure can greatly affect overall health and weight gain.