If you want to see real obesity, go to Miami

'It's more obvious because everyone wears shorts. And the entire airport smells of cinnamon doughnuts'

Here's something to chew over when pondering the growing problem of obese children. The fattest child in my daughter's primary school class was also the cleverest. Her mother came from Kuala Lumpur and latched onto me as a fellow Eurasian when we waited to collect our children after school.

Far from being worried or embarrassed by Hannah's Humpty Dumpty physique – at seven her daughter weighed close to 10 stone – she was obviously proud of what she called Hannah's "very good size".

At break, while the others played football, Hannah sat on a bench absorbed in the Reader's Digest or the Ladybird Guide to the Solar System steadily working her way through a family size pack of mini Mars bars. She came to tea once and explained why, although the individual galaxies were constricting, the universe itself was expanding. She wanted to be an astronaut.

I had just come back from a press trip to Hawaii where one morning all of us, apart from a Midlands radio presenter called Kenny, had been taken by helicopter to see some spectacular waterfalls. Kenny couldn't come because the tour guide said he was too fat and would upset the balance of the helicopter. I'd told the children about Kenny and hoped they wouldn't bring it up. They didn't because, believe it or not, they really hadn't noticed Hannah was overweight. "Hannah the clever one," they'd say, not "Hannah she's fat."

I wish this story had a happy ending for there's no reason why stories about fat people shouldn't. Take Kenny. From the neck down he looked like Mr Blobby but he had a surprisingly lean, mean profile and a devastatingly sexy voice. Women in the Midlands wrote in every week to tell Kenny how much they fancied him. When we got back from our waterfall trip, we found him on the hotel terrace drinking beer and dealing with his fan mail.

Hannah, I'm sure, could have ended up as content as Kenny, but at 12 she was screwed up by the therapist her mother got hold of to help her lose weight. Please note it wasn't Hannah who wanted to look like Kate Moss, it was her mother forcing her. From being a bright, happy, clever fat girl, Hannah became a depressed neurotic anorexic teenager who only read books about fashion and diets. I bumped into her mother the other day outside the Post Office. "How's Hannah?" I said. She was at a health clinic in Portugal doing alternate sessions of meditation and colonic irrigation, said her mother.

Since the obesity report came out, parents have been swamped with advice about how to control their children's diets and lifestyle. The older I get, the less I'm convinced that we poor parents have any control over our children at all. This depressing opinion was confirmed by Sir Richard Doll, the first doctor to discover the link between cancer and smoking. He was on Desert Island Discs, and when Sue Lawley asked plaintively what parents could do to stop their children smoking, Sir Richard said: "Absolutely nothing." In fact, he opined, the more parents nagged at children not to smoke, the more likely it was that they would. As long as they stopped in their mid-thirties, they wouldn't die of lung cancer, he thought, and there was a very strong chance they would stop smoking as adults having weighed up all the evidence against it.

I'm sure the same argument applies to obesity. Keep nagging at children to stop snacking, switch off the television and take exercise, the more they will guzzle and slump. Waiting outside the fitting rooms of a Kings Road shop the other day, I was surprised and dismayed not by how fat kids are these days but how unhealthily skinny they are, especially teenage girls. The ones trying on crop tops and trousers looked less like nubile young women than scaffolding.

If you want to see serious obesity, go to Miami airport. It's more obvious out there because everyone is wearing shorts. The entire airport smells of cinnamon, the preferred topping for all those doughnuts they're selling. You see entire families sitting at doughnut stalls with buckets of doughnuts between their knees. Now that's obesity.