IQ vs BMI

One of my friends is super-fit (she drops casually into a spilt like a rag doll), with the flattest stomach I've seen outside of Baywatch. She's also blessed with considerable height and real curves. As you can imagine, she is stunning. But she hides herself away most of the time because she thinks she's fat.

This is not a unique story. Slim girls who weigh themselves every day seem to look in the mirror and see only the extra half-pound of negligible water weight. Fat girls like me, who use the weighing scale as a doorstop, look in the mirror and see the body as it would have been if they had shed five pounds by doing the "bikini ready in four weeks" thing they'd cut from a magazine and put on the fridge a month ago.

It may sound like delusion, but it's actually just the joy of potential.

I did become bikini-skinny one time, through great toil and trouble. After the novelty of it wore off (about a week) it became apparent that I had not magically transformed into anything else. Not an elegant social butterfly, nor a brilliant, extrovert scientist. I still couldn't remember any jokes, let alone tell them. It had not lessened my workload, lengthened my weekend or helped me pass the slope test, not matter how easily I did it when practising with my driving instructor.

Basically, I was still me – but an unhappy, malnourished, uptight, weighing-scale-junkie version. The "unsuitable" clothes that I wear with exuberant pleasure in my overweight state were impossible to buy when skinny, because all I saw in the mirror was the extra half-pound of negligible water weight.

In other ways it didn't make a blinding bit of difference. I don't think my friends even noticed beyond the first few days. (In fact I expect one of them, reading this, to wonder when it happened though he was present at the time). The only one it mattered to – too much – was the boyfriend. This mercifully annoyed me enough to force me off the wagon.

So I was free again to take pleasure in being me. To enjoy the places I went, the people I met, the food I ate, the sun, sea and sand, without worrying about what I looked like doing it.

Years later, I let myself to be talked into joining a celebrated weight-loss centre. For two hours every day I was judged and found wanting by strangers that I did not respect or like. Day by miserable day, they picked and tore at my self-esteem (apparently your existing confidence needs to be destroyed before they can build their version in its place as promised). I have looked forward to dentist visits with more girlish enthusiasm.

The mental self-defence system kicked in 10 days later and I ditched the whole thing. Someone else I know tried it and reacted exactly the same way. This kind of "slimming centre" – its lying refrain of wellness, beauty, confidence, in equal parts hypnotic and nauseating – represents everything that is wrong with the world. The reason why millions of young girls are seduced by anorexia. Why my proficient, intelligent, extremely level-headed friend has inexplicably allowed a pretender called "body image" to get under her guard.