Rock music may stir something rebellious in us. It could inspire latent sexual urges. It sometimes reaches to the core of our being. What it generally doesn't do is make us think about the ageing process.

But when a 69-year-old man dressed in jacket, tie and trilby expends probably the same amount of energy as a Premier League footballer while entertaining 20,000 people for two-and-half hours, you can't help but wonder what his age-defying secret is. The first thing to say about Mick Jagger is that he has less body fat than the average HB pencil. You don't need to be a trained physician to work out that this may have something to do with his incredible stamina.

I don't know what Sir Mick's regime comprises, but should he ever need to supplement the millions he is getting for the Rolling Stones' reunion concerts, he could do worse than share his formula. A diet book, perhaps? You Can't Always Eat What You Want, or (I Can't Get No) Saltimbocca. It would be certain to be a best-seller, and be a lot less work than throwing yourself around the stage at the 02.

It helps that, for decades now, Sir Mick has eschewed the pharmaceutical temptations to which many in his line of work succumb, but you don't get to strut your stuff to such effect on the eve of your 70th birthday without exercising, and without exercising formidable self-control. Everyone has talked about the age of the Stones who took the stage for their 50th birthday gig on Sunday night they were a total of 273 years old, and their average age, I am reliably informed, was higher than that of US Supreme Court judges; but no one has talked about their weight.

Together, the four Stones couldn't be that much heavier than one Meatloaf, and while I wouldn't suggest that the Keith Richards modus vivendi points the way to healthy living or that Jagger's cadaverous look is to everyone's taste, the link between longevity and body fat is there for all to see. The fact that they are still performing to such adulation speaks, yes, for the durable appeal of their music, but also to the benefits of a macrobiotic diet and a strict fitness programme.

I am considerably younger than any of the Stones, but even now I find bending over to tie my shoelaces an effort, and one that should only be attempted in stages. The idea that, at 69, I could do anything on a Sunday night more energetic than watch Homeland is beyond my imagining. I didn't go to the 02; in truth, The Stones have never quite done it for me; but, having seen the clips of the concert, and hearing from awe-struck friends who were there, I have nevertheless had a mind-altering experience.

I have suggested in this column previously that the modern world, with the rapacious advance of technology, has made men in particular feel prematurely obsolescent. I am not suggesting we can become rock stars, but there's no reason why we can't eat less, drink less, look after ourselves, and get a second wind. Sir Mick, you're an inspiration.