"EAT your chips, or you won't get your KitKat!"

I tried not to listen, I really did, but the mother's voice carried across the caf like a fog horn in a light mist.

The woman and her husband were tucking into their fish and chips in the supermarket eaterie as if they hadn't eaten for at least a fortnight (although their waistlines told a very different story).

Their two sons and baby daughter were none too keen, however.

After straining my neck to get a glimpse of their plates, I couldn't blame them. Faced with half-a-dozen lacklustre, beige nuggets and a pile of insipid, beige chips, I think I might have had a tantrum too.

"Ryan, eat your chips or that KitKat is going in my bag," the mother continued, jabbing her fork at the offending three-year-old, before turning her attention to his siblings. "You can all forget about having any chocolate until you've cleared your plates."

I was sorely tempted to chuck my bread roll at her its rock-like consistency would have easily knocked her unconscious if I had hit her squarely between the eyes. But, instead, I made do with muttering under my breath: "Eat your lard before you have your sugar. Come on Ryan, let's hear those arteries clogging before all your teeth fall out."

Government statistics indicate that one-in-three youngsters aged two to 15 is now overweight. While I would query the accuracy of such a high figure there must be a really lardy school somewhere to balance out the bony bunch at my son's school there is no denying that our kids are getting fatter.

We can blame the food manufacturers, the supermarkets, the media and the advertisers as much as we like, but the fact remains that on a day-to-day level it is parents who dictate their children's diet.

The chips and ice cream don't appear in the freezer by magic, dropped delicately into place by Frosty the fat fairy while we sleep. Parents buy them. The crisps and chocolate bars don't sneak into kids' lunchboxes when we're not looking. Parents put them there.

And the money for sweets and fizzy drinks doesn't miraculously materialise in kids' pockets as they pass the newsagents' threshold. Parents give it to them.

The Government has threatened to weigh our kids at the ages of four and ten, and warn us if they are too fat. Critics have dismissed the mass weigh-in as misguided, costly and bureaucratic. It is also a monumental waste of time.

Parents can see when their kids are getting too porky. I'm pretty sure if my son or daughter waddled into the room one day with a spare tyre the Michelin Man would be proud of, the penny would drop.

We know when our kids are eating too much rubbish: they fluctuate wildly between complete, dead-eyed lethargy and bouncing-off-the-walls hyperactivity; they look pale and uninteresting; their mood swings make a woman with extreme PMT look like the image of clear-minded reasonableness; and here's the clincher they start to wobble when they walk.

Most of us know that fruit and veg are good and that beige, processed food is bad. Is it really so hard for us to drill this simple message home to our kids?

There really is no time to lose. We have to teach our children now before they have children of their own.

In the same caf as poor Ryan, I saw a teenage girl having lunch with her friend and their two kids, the eldest of whom was about two and the younger just a tiddler of a few weeks old. The children were beautifully turned out, as were their young mothers, but their eating habits were less promising.

As one mum liberally doused her daughter's chips in salt, the other sucked a KitKat, rubbed the melting chocolate over her baby's dummy and shoved it into its mouth.

It doesn't happen often but, for once, I was speechless.