Rhiannon Harries: Health and fitness, fine. But what's with this modern-day obsession with perfect bodies?

What is the anti-smoking lobby going to do with David Hockney? There he was on last week's edition of The South Bank Show Revisited, in fine fettle at 72, sharp, energetic and talking extraordinary good sense. "I was sitting on a bench in Holland Park – watching the rabbits and the magpies," he recounted. "I lit up a cigarette and three great big girls go jogging by, see me smoking and wag their fingers at me. They think they're very healthy – they're totally obsessed with their own bodies and never saw the rabbits or magpies. They think they're healthy, but I think I'm healthier. That's my odd view of it."

Perhaps it's just because I too am fond of idling – sorry, contemplating nature – on park benches with a cigarette in hand (it's the only place you can sit and smoke nowadays), but Hockney's assessment doesn't sound in the least bit odd to me. Being "healthy", we are told by everyone from the Government to ever-diminishing Girls Aloud stars, should be top of our priorities. OK, got it, thanks, but what exactly does "healthy" mean? Being free of serious illness? Having a body like Madonna? Only drinking alcohol on weekends and Wednesday?

Hockney may be lucky to have exceeded his three-score-years-and-10 on 40-a-day, but I wonder if his Lycra-clad ladies will all make it to 72? Jogging round a park three times a week isn't a guarantee of immortality, or even longevity, so why the smug faces? And frankly, if spending two hours a day in the gym came with an assurance of an extra 10 years, I'm not sure I'd want them.

Regular exercise is a brilliant thing for body and mind, but what Hockney skewers is the weird fixation that we have developed, relatively recently, with our bodies. Instead of caring for them, quite rightly, as precious tools that enable us to enjoy other things, we have made them an endpoint in themselves. Check out any dating website and you'll see that half the people on there actually list "going to the gym" under "interests".

I hope most of them are lying – it's certainly tempting, since there are plenty of finger-wagging joggers ready to sneer at your comparative inertia. We may have become more liberal, by and large, in this country but health – be it smoking or obesity – is one spot we still get to stick the collective knife in a little. Thank god, then, for everyone who hasn't gotten round to turning their body into their masterpiece, because some of them, like Hockney, might find the time and the imagination to create something a whole lot more impressive elsewhere.