While the world continues to speed down the dual carriageway of delight, I bend away on the slip road to dotage, fumbling for change as I approach the toll-road of terror: I am 40 in three weeks. There are two options. I could gently extract myself from public life and prepare for a hermit-like existence of non-washing and self-muttering. Or I could run at the problem head on, change my name to King Canute and instruct the tide to turn back. I opt for the regal, Danish approach.

To arrest the steady development of the ageing process I need a combined and sustained assault on my entire being. I need a detox. So I make for Slovenia. Ljubljana to be precise, a city famous for having too many consonants. An hour outside the city is the small town of Toplice and the Hotel Vitarium, where I am promised a seven-day induction into wellness in the form of an holistic VitaDetox progamme.

[I should have read the letter sent to me before I left London. It explains that for the detox to be most effective, and to mitigate against a negative reaction to the dramatic changes in my body, I ought to prepare by weaning myself off coffee, red meat and cooked food. Then my big brown burly body would have been readied for its transformation into the new ready-to-be-40-but-with-the-body-of-a-32-year-old me. Instead my last meal at Stansted airport is an all-day breakfast muffin, a coffee and a cute little mince pie. ]

When I arrive I am hooked up to a Futrex machine that measures your body fat, the percentage of lean fat, your body water, your national insurance number... It transpires that I am in a mess. I weigh 105.5kg (16st). I laugh and claim that I am not fat, merely big-boned. Then they measure my bones, which are actually of average size.

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I am officially, scientifically, fat. My body fat percentage is 26.6 per cent (BMI of 32.8), just within the category alarmingly referred to as “risky”. And my blood pressure is high. They tell me that my ideal weight is about 90kg, which means I have to drop 15kg (that's nearly 2st). But dropping my weight will mean my BMI will fall and my blood pressure will dip to somewhere more acceptable for a man of my age. Anita, the nutritionist, tells me that I'll have lightly-boiled vegetables and salad for a day, then a three-day programme of juice. Much as I love food and am bound to miss it, I like juice, especially freshly-squeezed juice that combines celery, apple and ginger.

Day two and I have two juices for breakfast; a consommé and two juices for lunch; the same for dinner. Never before have I sustained myself solely on the stuff. And never before have I attempted such gastronomic denial while attending Pilates at 10am, water aerobics at 11am, Nordic walking at 2pm and various other procedures in the afternoon.

By the middle of the afternoon, four juices and a consommé down, I feel terrible. My head aches and I feel exhausted. After lunch I crawl back to my room, cancelling my afternoon, and sleep. I haul myself back down for a dinner of spinach juice, mixed vegetable juice and, of course, consommé. Then more sleep. The next day is the same. A couple of hardened Dutch detoxers (women in their late forties) sympathise. One says that she had a similar reaction to a juice-based diet but assures me that by the end of the stint I will feel amazing. I smile politely and doubt her sincerity.

After a couple of days' inertia, I take advantage of the hotel's saunas and pools. I love saunas. But I have never been to a central European sauna before. Bloody hell. Men and women wander about. Utterly naked. They share saunas. Utterly naked. They stand and chat in groups by the dipping pool. Utterly naked. There is a lot of nakedness going on.

I have never felt so uncomfortable. Never. No-one has seen my utterly before. I have no intention of being naked. I'm British, for heaven's sake. Add to that the fact that I am the only brown man at the spa - if not in the town - my discomfort knows no bounds.But by the final day I feel great. My headaches have gone, I have worked through the fatigue and I am back on salads and fish.

My final assessment by Futrex shows that, astonishingly, I have lost 4kg (9lb) in five days. Only 11 to go! My BMI has dropped by 1.3, but is still too high. I am impressed. But the results, apart from being dramatic, are part of a bigger development. Having lived the detox way for five days, I have had time to rationalise the approach. Rather than use a gym and eat as I normally do, in the hope that one activity offsets the other, I adopt the Hotel Vitarium's holistic approach. I change the way and the amount I eat. I drink less coffee and have cut right back on the booze.

Maybe life does begin at 40? For me, an understanding of health and wellbeing certainly has. I can't wait until I return to the land of juice, colonics and naked saunas.

Ambience Set in beautiful countryside, the four-star hotel is Scandinavian in design and ambience. The Vitarium spa is all dark wood, frosted glass and mood music. Yet there is also the feel of a sanatorium about the place, something more straightforwardly medical. This is because about 30 per cent of the visitors are there for the cardiac and rehabilitation clinics, their stay paid for by the Slovenian Government. There are crutches and wheelchairs aplenty. The remaining 70 per cent seem mostly to be wealthy Dutch, Germans or Italians. There are very few Scots of Indian descent.

Wallet watch The VitaDetox is a seven-day customised programme for €512 (£500) that includes advice from nutritionists and a personal trainer. Health analysis, detoxification treatments including massage, exercise such as Pilates, and relaxation activities such as thermal baths, are all included. Accommodation at the Hotel Vitarium costs from €466 (£455) a week per person, and includes bed, breakfast and dinner, plus use of the swimming and thermal pools, saunas, etc.

Need to know For more information on the spa and packages, go to www.terme-krka.si. EasyJet flies to Ljubljana from £60 return (www.easyjet.co.uk) .

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