How many 'portions' of television contributes to a healthy diet?

Only caught a snippet of last night's BBC - Radio 4 - PM report on children and television that included an interview with Dr Arik Sigmund who synthesized the findings of 35 major studies on the affects of television on children. [Note to BBC: please post a podcast of it on the PM site]. In brief, Dr Sigmund's point, as I understood it, was this: too much TV is very, very bad for kids' brains and (expanding) butts. Speaking for the 'other side' was a bloke from BBC children's TV who argued that 'correlation doesn't mean causation', i.e. just because TV addicts can't concentrate and tend to be obese, doesn't mean that it's TV's fault. And even if there is a problem, he added continuing his Big Mac Defense, don't blame us, we just make the stuff; it's up to the consumers - kids and their parents - to take responsibility for their own media consumption habits.

Reminds me of the ongoing discussions around the use and abuse of alcohol, which are also in the news this week ( "12-year-old Scotch may be the greatest alcohol, but 12-year-old Brits are the greatest alcoholics" ). The contribution by public health professionals - and the some industry players - to the debate has been to promote 'responsible use' - AND to articulate what that means, i.e. guides on how many units a day are acceptable, etc.

• Suggestion: Perhaps the BBC - which aims to not simply be a public broadcaster, but a public good - could work with researchers (such as Dr Sigmund?) to develop guidelines for parents (and others) on how many minutes/ hours a day of 'screen time' would be acceptable as part of a balanced media diet.