I’m sped from the airport by a James Bond-style driver dressed all in black. He plays New Age dolphin music, the sort that normally goes with massages and crystals. Is he getting me into the mood for the Sha Wellness Spa, the world’s first five-star macrobiotic spa, on the 50 minute drive from Valencia, Spain? Soon the spa looms like an ocean liner stranded among the Sierra Helada mountains, with the Lego tower blocks of Benidorm in the distance. Outside, one of the first of its endlessly solicitous staff welcomes me with a hot flannel. Then we enter the 28,000 square metres of white marble, water features and calm.

The clinic offers a fusion of Oriental and Western natural therapies, anti-ageing and non-invasive techniques. Sha is based on the ideas of Michio Kushi, a macrobiotics guru who believes that food is the key to health and health the route to peace. It was started by a property developer called Alfredo Bataller Parietti, after he was rid of a tumour and realised the body’s potential for curing itself with a macrobiotic diet and natural therapies.

A macrobiotic diet involves lots of grains, beans, fresh fruit and vegetables and avoids processed foods and animal fats, plus it includes the correct balance of acid and alkaline foods. If it’s good enough for Gwyneth and Madonna, I reason, it should be alright for me. Sort of.

First I’m shown round the spa. There’s a heli pad, chapel, gym, Aqua Lab (for water therapy treatments), Oxygen Bar (with bottles of oxygen to suck from while you’re waiting) and reception area with a display cabinet. Instead of Rolex watches or Dior handbags it contains soba, sea vegetables, nori flakes and spelt grains. Nearby signs indicate that the clinic offers ‘Sleep Medicine’ and ‘Anti-tobacco medicine’. Then I’m led upstairs to my suite (the spa has only suites), a Japanese-style oasis.

Next is a lunch of modern macrobiotic haute cuisine – think Heston Blumenthal with sea-weed (the chef, Pablo Montoro Fernandez trained at El Bulli). The dining room has mother-of-pearl look nightclub walls, a lotus pond, a floor of Arabesque white marble and Japanese dark wood tables. It’s also full of cashmere clad singletons treating their bodies as temples. I’m served lobster and sprouts in what I suspect is mud, followed by little black flying saucers of squid ravioli, then ice-cream decorated with beetroot crisps. The macrobiotic way is to chew each mouthful 54 times: I wonder why they don’t just serve it ready-masticated.

Afterwards, I meet the nurse for a health check in her office. I have dodgy knees (too much competitive running), a touch of eczema and sinusitis (after the flight). But broadly I’m extremely healthy plus caffeine, alcohol and nicotine-free. My aim is simply to lose a few pounds, read Wuthering Heights and go cold turkey on my BlackBerry. The nurse records my blood pressure, weight, lung capacity and fills in a health questionnaire. ‘Headaches, constipation and peeing a lot often happen when you start a macrobiotic diet,’ she warns, before adding that my weight is within normal range.

I’m to follow the spa’s Discovery programme – the price of which includes nurse and macrobiotic doctor consultations, a special diet, daily therapy (shiatsu to massage) and activities from yoga to meditation and talks. My diet will be decided after a consultation with the macrobiotic doctor. I’m anxious that I’m just going to be served minuscule portions of beans.

The next day I see Bill Tara, an American macrobiotic doctor with 45 years’ experience. Using the Oriental diagnosis of Bo-Shin, he considers the colour of my eyes, skin texture and temperature, checks my pulses and diagnoses which organs are under stress (kidneys and adrenal glands, apparently, from overworking). Bill personalises my diet which includes breakfast of miso soup and barley porridge with almond milk plus shitake mushroom tea (a Japanese medicinal tea to help the liver release toxicity) after every meal.

Over the following days, Bill gives great health talks on topics like food and science. At other times, I lie in a flotarium of Dead Sea water with illuminated stars on the ceiling (a waste of time and my head keeps banging against the edge of the pool); have a world-class massage (think magic hands and orange oil); join excellent yoga and pilates classes; and get wet in the Aqua Lab – a brilliant therapeutic water circuit with water beds and jets, pebble bath, caldarium, tepidarium and hydro pool, overgrown taps gushing water to massage your back and a Niagra Falls for pummelling the shoulders.

The rest of my hours are spent on the loo (diuretic, detoxing foods rule OK,) or getting lost looking for loos. Luckily there are four ladies’ lavatories by the restaurant. I’m taken aback when I get a call from reception saying, ‘You must come down for wee’, but it turns out they only want to weigh me.

Recently Bill busted some Sha-ites at the nearby Ben and Jerry’s bar but I follow the programme exactly and, to my surprise, I don’t feel hungry between meals. My Discovery meals are sensible portions of things like carrot soup, beautifully presented vegetables, tofu and barley followed by red fruit jelly. Or leek soup, salmon tartare, quinoa and seaweed then more fruit jelly. I don’t feel bloated afterwards, I have no cravings and feel, if not virtuous, then certainly almost virtuous.

A highlight of the week is a cookery demo with Marlene MacMillan (who spent a week teaching Rupert Everett to cook). Talk amongst the participants is about people who sleep on magnetic beds, how the Japanese don’t even have a word for menopause (because, being macrobiotic, they don’t suffer its effects) and how miso cleanses toxicity from the body. Meanwhile words like ‘shoyu’, ‘tempe’ and ‘daikon’ are bandied, and I learn to make a mean miso soup.

The demo is interrupted for me when I’m called to a colonic irrigation appointment. I had mistakenly thought that the clinic was offering a radical new treatment: a colonic done with coffee. And by this stage, I’m happy to get caffeine into my body any which way but it turns out that it’s just a normal colonic – cappuccinos are only administered via enemas – and simply involves tummy massage and jets of water up your you know what. I watch food that has been chewed less than 54 times leave my body bobbing along water in a clear pipe, and afterwards feel light-headed and less gassy.

To feel any changes and gain scientifically measurable effects, a week is the minimum recommended stay at Sha but I have a good ‘taster’ in four days. If you go for longer, they can do genetic testing to check, for example, if you’re prone to obesity, and monitor things like thyroid function and cholesterol. On my last day the nurse excitedly shows that I’ve lost nearly two percent of my body fat. Then she weighs me. I’ve lost 200 grams. That works out at least £8 a gram. Even at that price, I’d go back again. I’ve learnt 50 things to do with seaweed and I’m keen to make some life changes. I realise I’ve been drawn to the macrobiotic way of thinking when I get on the plane and someone asks, ‘What’s it like in London?’ and the hostess replies, ‘Lots of grain’.

Since my return, I’ve been avoiding wheat, sugar, caffeine, dairy and my cannibalistic tendencies. Plus I had a great follow-up colonic with Caroline Shaw at the Hale Clinic. My Sha experience has left me with sparkling eyes, a glowing complexion and feeling calm. But it has also left me miserable. Now everyone tells me that that’s because I’m detoxing…