Shop and drop a size

Oh the joy. On the very day that the final episode of Sex and the City is to be aired, when all of us who have sought to emulate Carrie's spending habits thought we might have to give up retail therapy and do something more useful, like take up kick boxing, comes the news we have all been waiting for. Shopping, according to new research, is actually good for us.

Apparently, women notch up 133 miles a year, burning 193 calories per session, just by wandering around the shops. We clock up a staggering 4,059 steps per trip, which is nearly half the magic daily number of 10,000 steps, beyond which you get "significant health benefits".

Hmm. Can this really be true? I have, of course, increased my beats-per-minute significantly in the past by attempting to use my credit card when it was dangerously over-limit (those terrifying moments before the little machine decides whether to let me have that Prada dress or not), but apart from sprinting to be first in line at the Gucci sale, how hard can shopping be?

The stores on Bond Street are all full of lovely squashy sofas and glasses of bubbly. The new Martin Margiela store on Bruton Place might have a basketball net installed in one corner, but no one seriously expects you to use it. They haven't even provided a ball.

Anyway, in the interests of science, I took myself off to the Whiteleys mall in Queensway, where I would meet fitness and nutrition expert Joanna Hall to see if shopping really was going to keep me fit and lithe.

I have always in the past thought that working out is evil. I haven't exercised on purpose for two years - ever since running gave me pneumonia. Well, it was that or the cigarettes.

Joanna turned out to be highly sceptical about the whole thing. Isn't carrying my handbag and several designer carriers going to do my triceps the power of good?

"Just holding them won't firm anything," she says strictly, "but if you are swinging your arms, you will get some benefits to your shoulders."

She recommends a bum bag instead of a handbag; less stylish, but it will mean your weight is distributed more evenly, which is better for your back.

If possible, ask for carrier bags with long straps; that way, you can wear them across your body - much better for your posture. This also frees up your arms for pumping as you walk. "If you pump your arms, your legs will follow through," says Hall. And freeing up your hands helps with that essential fingering through the rails.

Shoe shopping is also good; think of all that bending and walking up and down. Trying to do up a difficult bra is also a little bit like yoga, surely.

First, though, you must make a shopping list, to give you more purpose. According to Hall, merely wandering aimlessly between stores just isn't good enough. The idea is to go for what she calls "walking with intent", the way you move when there's a sale on. Don't dawdle, think of it as "active travel".

Hall says the optimum walking pace for a good workout is five per cent slower than the moment just before breaking into a jog; only then will you get any kind of aerobic benefits. I think this may be a tad speedy for really effective retail perusal; just go as fast as you can.

Another top tip is to cross your feet in front of each other as you walk; this can do wonders for your obliques. Pushing a buggy can also help your bum; just think of all that extra weight you're pushing in front of you. The objective is to work up a sweat although, obviously, you might not then want to try on any clothes.

If you have shin pain, as many do if they are unused to moving about much, walk on your heels for a while. Weird, but it works.

The one advantage malls have over Bond Street, of course, is the great escalator challenge. First, you need to find one going in the right direction, which could mean a hike of up to five miles; and, second, because they are quite springy, you can charge up and down them without risk of injury to your joints.

This brings us to the other, overwhelming factor that means shopping must be good for our body mass index: the full-length, over-lit mirrors in changing rooms which are teeming with 16-year-olds. A visit to Topshop in Oxford Circus is enough to make any grown woman swear off the Krispy Kremes and rush home to perform 100 sit-ups.

And the final incentive to shop, rather than spend your lunch hour in Holmes Place? I was £101.14 lighter after my little experiment: I bought two books, a handbag, two T-shirts and a Mother's Day card.

What more could a girl ask?