I’m seldom in favour of bans — they presuppose unimaginable stupidity, and I like to cling to the forlorn hope that this country isn’t, in fact, entirely populated by morons — and Ofcom’s decision seems like a drop in the ocean at best and pointless at worst. It’s quite likely to result in at least one commercial network getting rid of its children’s output altogether, which isn’t what I’d call a result.

More to the point, the consumer watchdog Which? pointed out last week that advertising has anyway long since moved on, and that its most insidious and captivating examples were no longer to be found on telly but online. Manufacturers of health-sapping rubbish are determined to get hold of our children by whatever means and they’re succeeding, by disguising their ads as games, e-mailable “fun” video clips, phone texts, and so on.

Given that it is impossible to monitor how one’s children spend every minute of their time online — you can hardly install a program that blocks sites containing words such as “sugar” — it seems blindingly obvious that the solution to the problem of nice children turning into pasty slugs by the time they’re 10 needs to be parent-based. But if that’s to happen then parents need to stop lying to themselves.

I was as incandescent as anyone else watching Jamie Oliver’s first school dinners series, and whooped with approval when, in the second series, he called parents who still fed their children lardburgers and junk “arseholes”, but the truth of the matter is that we’ve all done it.

My weekly Ocado shop tries its hardest to be organic and sugar-free, but of course it isn’t, entirely. Like many parents, I have somehow got it into my head that “treats” mean occasional sweets, crisps, chocolate and the rest; and that, for instance, yoghurts are “healthy” (they are loaded with insane quantities of sugar). I know, rationally, that this isn’t the case, and that I am harming my children’s health, but old habits die hard. And given that, like most middle-class parents, I don’t want to become a food Nazi — my generation was brought up on the notion that a little of everything, in moderation, does no harm and stops you being a ghastly weirdo food bore — I find that there is a discrepancy between what I say and what I do.

We may hang out at the farmers’ market on Saturday morning, for instance, but then we may come back via the park and the ice-cream van, in which case hello pig fat and sugar so-called ice-cream — with a flake thrown in for good measure.

I huff and puff indignantly when I see photographs of women whose children are fortunate enough to be fed balanced, Jamie-style meals at school shoving burgers and chips through the school gates — but my children eat chips too.

I am agog when I see schoolchildren (with terrible skin, more often than not, even though they’re pre-pubescent) in the newsagent’s buying their “lunch” — crisps, fizzy drinks and chocolate — but when my sons go and hang out in central London at the weekends, I doubt they’re feasting on chickpeas.

A survey last month by the British Potato Council found that vast numbers of women tell “little white lies” about their children’s diets to save face with their families and friends. Social pressure, arising from Jamie-style programmes and media comment, means that women lie most about how their children aren’t allowed chips or other fried foods.

The second most common lie is for women to tell friends that their children eat only fresh, home-cooked food. Other lies include chocolate only at weekends, the full quota of five portions of fruit and veg a day, no frozen food, and the improbable old chestnut “they actually prefer healthy food”. They don’t: if they did, we wouldn’t be in this mess.

Having spent the past year writing and researching a diet book, I have come to the conclusion that sugar is the devil. It’s in absolutely everything, from fruit to milk to every monstrous trans-fatted, ultra-additived thing, though of course there is a difference health-wise between naturally occurring sugars and the refined white kind. The point is that I have veered from my original position — everything in moderation — only as a result of a gigantic effort to try to understand diet and nutrition.

Most people don’t have the time to do this. They go to the supermarket, read a label that says, promisingly, “60% fruit”, and don’t stop to ask themselves whether that means the remaining 40% comprises sugar, fat, or both. Instead of sneering at these people — time-poor working mums with a couple of vocal toddlers wedged into the trolley — for being uncomprehending, stupid and careless, we need to find a way of giving them proper information. It is simply a fact that diet bears a direct relation to behaviour, concentration and academic achievement as well as weight (a study by the Scottish prison service and the Home Office has already found that improving the vitamins, minerals and fatty acids in the diets of teenage prisoners appears to reduce antisocial behaviour considerably).

At the moment, only the middle classes seem to have got the gist of this, and even then, only in the vaguest terms, because it’s actually quite complicated, to say nothing of expensive. The working class, languishing behind, are getting fatter and fatter; their children are underperforming. It’s hard to see what they’re supposed to do about this, when as a nation we cling on to the belief that things that are appallingly bad for us — drugs, cigarettes, drinking to excess, junk food — are life-enhancing treats.

Anyone who says otherwise — see the ridicule heaped upon Gwyneth Paltrow for her devotion to macrobiotics — is seen as a joyless bore. That she’s unlikely to keel over from a heart attack in the next 10 years is dismissed as an irrelevance: what a grim life she must have, we think, gnawing sadly on sprouted mung beans.

Banning junk food ads a few hours a day isn’t going to change that attitude, or halt the decline in our children’s health. Companies that peddle this stuff to our kids are actively harming their health: surely that warrants a great swell of grassroots anger, instead of a half-hearted shrug and a despairing “everything’s bad for you these days”.