The Labour party have said that their manifesto will contain a pledge to extend the ban on advertising fast foods until the watershed. I think that's 9.30pm. When I heard the news this morning I was surprised that we still had a watershed! Because it appears that from pretty early on in the day language that used to be described as foul and explicit sexual content litter our popular television and radio. And I don't just mean the propensity of Women's Hour on Radio 4 discussing female sexual health at morning coffee time! But even the enforcement of a watershed on crisps but not sex is not my real issue.

Over indulging in fast foods is clearly bad for your health. And as a fat man who knows that he should be more careful about what he eats I am in no way opposed to the government giving sensible nutritional advice. But I doubt very much that it is advertisements for McDonalds that lead to children bleating at their parents until they surrender and take them to the golden arches for their e-number fix!

Our issues with obesity are far more complicated. They are the result of increasing amounts of cheap processed foods, that have led to a culture of not cooking amongst many of the poorest in our society. This has been coupled with increasingly sedentary jobs. Physical labour is hard to come by these days. The navvy has been replaced by machines. Very few of us get a sweat up at work. And whilst it's all good and proper to tell people to get out and get some exercise, the fact that they are working longer hours makes that hard for lot of folk.

But my problem is not the over simplistic ban on fast food adverts. It's the way that our culture has lost the plot on what it can and can't legislate on. We've decided that we must legislate about what people can eat, but we can't legislate or advise on what is a normal healthy sexual relationship or what is normal family life.

So I'm fat and I'll admit that is a problem. My body is designed (I believe...) to function effectively within particular ranges of nutrient intake and energy output. I'm happy to be told that and given the information I need to choose to eat and exercise appropriately.

My body is also designed to operate sexually in a particular way. I have particular sexual organs that are designed to be used with the corresponding sexual organs of a woman. It is also the case that individuals and society as a whole function most effectively when this sexual relationship is limited to one partner in a life long commitment. This is what used to be regarded as the normal family unit. None of this requires any acceptance or understanding of the Bible, it is merely deduction from human biology and sociology. But you won't find any political party advocating it.

I'm not suggesting that we should return to trying to legislate people's sexual behaviour, merely that we should offer the same level of honest education to our children about sexual health and ethics as we do about eating too much salt!

And what about us who are Christians? How can we help our kids negotiate the minefield that is modern television programming and advertising? Well the apostle Paul says:

"...whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things." (Philippians 4:8)

Which will probably mean that we need to feed them with a knowledge of Christ much more than a visual diet of crips and casual sex!