Health Dept, in Central London, aims to combine nutrition, exercise and psychology to maximize health. Its clients receive one-on-one coaching from Pete Williams, the 34-year-old scarily fit-looking owner and its chief instructor, or one of his two überqualified colleagues. Pete asked me to tell him about my lifestyle. I described a breakfast-less beginning to the day, mid-morning coffee with lots of sugar, a sandwich and pint in the pub at lunchtime, the odd packet of crisps and chocolate bar as an afternoon snack and a big dinner washed down with a bottle of wine. I also revealed that I never took any exercise beyond a gentle stroll to the pub.

“You have described a perfect recipe for putting on fat,” Pete said. “No exercise, lots of booze, a big meal at night. That’s why you’re getting man-breasts.” I blushed. My fatty chest was packed with the female hormone oestrogen, apparently, but exercise would generate manly testosterone. The answer, Pete said, was to raise my metabolic rate and become more active.

Or buy a bra.

After a series of physical tests, Pete outlined a programme and sent me off to get my blood tested. He explained that I must detox for three weeks on a diet that excluded potatoes, wheat, dairy products, caffeine, alcohol, red meat, sugar, cereals — almost everything that makes life civilised — and exercise at least three times a week; twice a week under the supervision of Health Dept staff and once under my own steam at a local swimming pool.

The detox diet sounded Spartan: fruit, vegetables and pulses, with small amounts of fish and chicken and the odd egg. Also the prospect of going without alcohol for so long was daunting. Pete said it didn’t matter if I had a single glass of wine now and then. I almost hugged him. I started the diet on a Monday and the next day I had my first session with Pete. The ethos at Health Dept is to maximise the efficiency of the exercises, and medicine balls feature prominently. On the walls are inspirational, if occasionally puzzling, slogans such as: “Pound for pound, sugar is better for you than cornflakes”. In the loo, a message just above the roll of paper on the wall reads: “A squat utilises 70 per cent of the body’s total muscle mass. It is full body training in one exercise”. After eating all that fruit, I squatted and lost a couple of pounds there and then.

Also on the menu were lunges, press-ups, tricky yoga moves and, best of all, boxing. I’d never done any boxing and was shocked at how much fun it was to pound away at the pads held by Pete while he yelled: “Jab, jab, jab; one-two, one-two; cross, cross, cross, cross . . .”

Pete sometimes gave me homework. On one occasion, with both of us lying on our backs on the floor, he urged me to practise tensing a band of stomach muscle. “Imagine you are sucking air up your butt,” he said, arching his back a little to demonstrate. As he did so, a 3kg (7lb) medicine ball leapt off its rack and rolled along the floor towards him. I knew he had strong stomach muscles but this was in Superman’s league.

Two weeks into the programme, I had a physical epiphany. One Saturday afternoon, pondering whether to take a long, healthy walk home after a shopping trip or to grab a taxi, I saw a bus 100 yards away — and sprinted for it. I could feel the power exploding in my thigh muscles as they propelled me down the road. And guess what? I caught it — but I was so breathless I couldn’t ask the driver for a ticket.

The diet I found more of a problem. Though I ate prodigiously, I was permanently hungry. And after one alcohol-free week, I was gagging for a pint. My resolve was stiffened when Pete phoned me with the results of my blood tests. Apparently, before the detox my liver had been in overdrive. Too much booze. “It doesn’t mean your liver is damaged, it is just working very, very hard,” Pete said. The news got worse. I also had high levels of uric acid in my blood and I was heading for gout. Whoopee.

Despite this warning after two fairly virtuous weeks, I fell off the wagon — big-time. I went to the pub on a Saturday evening with my flatmates to watch the England rugby team get beaten by France. Feeling upset about the game I decided to get absolutely trollied. I was the life and soul of several parties and ended up at somebody’s flat in Waterloo, sleeping on the sofa and snoring like a foghorn. Sunday’s hangover was accompanied by terrible guilt. I promised myself that I would behave for the next week and, to my surprise, did so. All that week I woke up feeling fantastic, clear-headed and full of energy. And on Friday evening I officially ended my detox.

Sitting in the pub having a celebratory pint, I felt oddly glum. The beer tasted alien, wrong. I had liked waking up and bouncing out of bed; I had liked the clarity of mind the diet gave me. And I promised myself that I would try very hard, from now on, to embrace the healthy life.

After five weeks of working out, Pete did a final assessment. I had lost only 3kg in weight but he told me not to worry. “Fat has turned to muscle,” he said poking me in my still largish but much firmer stomach. Best of all, my waist was 12.7cm (5in) smaller. “You did pretty damn well,” he said. A few days later, I strutted into the gym at T he Times and signed up. After I finish writing this, I’m going for a tough work-out. But then I’m going to take a gentle stroll to the pub.

Hour-long sessions at Health Dept cost between £80 and £120. For more details contact Pete Williams, Health Dept, 4-5 Broadstone Place, London W1 020-7486 3386; www.healthdept.co.uk

MENU MASTER

You don’t have to eat badly just because you’re detoxing. Here is my recipe for a good filling supper.

Paprika roast chicken with vegetable chips, lemon leeks and broccoli<br>Serves 1, takes 50 minutes

1 large organic chicken thigh (with skin on)
1 carrot
1 parsnip
1 lemon
2 leeks
1 small head of broccoli
Olive oil
Salt and paprika
Ground black pepper

Method

Brush the chicken thigh with olive oil, both sides. Sprinkle with salt and loads of paprika and place on a baking tray. Peel and cut the carrot and parsnip into 3cm-4cm (1½in) long, 1cm wide pieces, roughly the same size as chips. Scatter around the chicken and drizzle with olive oil.

Place the baking tray in the centre of a pre-heated oven (200C) for 45 minutes, basting the chicken and turning the “chips” once.

The chicken is ready when the juices run clear after you pierce it right through with a knife. If the “chips” look like burning, turn them again in the hot oil.

Chop the leeks and wash them thoroughly in a bowl of cold water. Remove the leeks — but don’t shake off all the water — and put them in a large pan with two generous slugs of olive oil, salt and freshly ground pepper. Cover the pan tightly and put it on a low heat for 20 minutes. Stir once halfway through and re-cover. When the leeks are cooked, turn off the heat and add the juice of the lemon. Cut the broccoli into small florettes and steam or lightly boil for a few minutes. They should be just a little crunchy when eaten.

Serve the chicken on a bed of “chips” with the vegetables on the side. The leek juice makes a delicious lemony vegetable gravy.