Vanity turned me into a gym addict

Maybe I'm a tad vainer than the next man, but beauty has always been a big incentive, which is why this summer I've unveiled the new me. Not only did I hire a personal trainer 18 months ago, having bruised my ego during a similarly hot summer, but I've just upped the ante to a six-week, intensive, four-sessions-a-week programme.

Two weeks ago I even found myself in one of those dodgy subways underneath Charing Cross station in a bleak-looking store stacked with shelves selling nothing but strangelooking protein powders for dedicated body builders.

For someone who used to loathe all forms of exercise - especially gyms - I've become something of an obsessive, constantly marking my weight and admiring newly-honed muscles. I confess, I've become an addict, and no one's more surprised than me.

My trainer - James, a former soldier who fought in Iraq and is, as a result, both big and bossy - had complained that I wasn't eating enough to sustain my current muscle growth, so recommended a new range of protein powders. Protein powders? Muscle growth? As a few friends have recently pointed out, with not a small element of surprise, my obsession knows no bounds. Surely there are easier ways to look good in a T-shirt, they argued. Sadly, there aren't.

I'm currently taking my first week off work since last July. I'm exhausted. But instead of heading off for a few days to Sardinia, a city hop to Antwerp or a jaunt to Jamaica, I'm spending each day at the gym.

I've been mixing my revolting, chocolate-flavoured Met-Rx Engineered Nutrition protein-plus drinks - to be taken twice a day - and making sure that I eat lots of fish and chicken for protein. (A while ago I stopped eating red meat, wheat, dairy products, tea and coffee - although I do make an exception for dinner parties. I might have become a gym bore but I am determined not to become a food one, too.)

I am now, rather extravagantly, a member of two gyms: No One Aldwych, a swish, discreet sanctuary in the basement of the eponymous hotel near my Covent Garden office, and another less-swanky one near my apartment in Shoreditch that I use at weekends.

I work out with my trainer during the week, mostly with weights, but do cardio on my own at weekends. I can only think of two occasions in 18 months when I've cancelled through illness: come rain or shine, flu or virus, I'll be there.

There are, I suspect, three main reasons why I've turned into a minor-league gym addict. One is my annoying competitive streak, two is a more than healthy dose of vanity (we're back to those summer outfits again), and three is the fact that - and I must confess, this one surprised me - it turns you into a brighter, sharper, happier person.

When I first joined the gym, I was doing 30kg barbell benchpresses, I'm now lifting 135kg ones. Sadly, I find this enormously gratifying. And why not? It's an achievement. I set a goal, however superficial it may seem, and I got there.

But what I find most intriguing and, admittedly, slightly addictive, is watching my body change shape. It's like being a sculptor and slowly chipping away at some, and building up other, parts of the body, creating an aesthetic that you (and hopefully a few others) will find more pleasing than the lump of clay you were originally presented with.

Although I'm definitely talking more Royal Academy Summer Exhibition entry than Old Master retrospective, there is still a feeling of empowerment. And feeling and looking fit does make you feel and look more confident: your posture improves and so does your confidence.

If only more London men were like me, the parks would be a lot more picturesque on a sunny weekend afternoon.