You can only detox properly when you've got time to do it. And a weekend is the perfect opportunity. I'm going to cleanse my body and mind and feel energised and fresh. My skin will glow, my hair will shine and I'll mysteriously lose half a stone. When I've bought all the carrots that is.
"You know who's a big fan of detoxing," says Vanessa, "Michael Jackson. I'm sure I read that somewhere. Be careful you don't end up like him."
"It's okay. I'm not taking Wacko as my role model," I say. But a small seed of doubt has been sown.
I struggle in from the supermarket the next morning laden with vegetables, brown rice, water and beetroot. "Hmm," says Vanessa, biting into a chocolate eclair. I shoot her a look of hatred.
"You'll stop laughing when I've cleared all the toxins from my body," I say snootily. "I'm sure I will," she replies, munching happily.
The problem with detoxing is that it doesn't leave you much time for anything else. By Saturday afternoon I've done nothing but prepare a kidney tonic, a liver tonic and stir vegetable soup. And I've got a blinding headache.
"Cheat and have a paracetamol," says Vanessa.
I don't. Wacko wouldn't approve. That evening I go out for a meal with a group of people I don't know that well. By the end of the evening, when I have explained for the nth time that my choice of food (mixed salad with olives, washed down with mineral water) is because of my detox, not a New Puritanism, I am convinced that they secretly think I'm a member of some strange obsessive cult. Attempts to spread the word about the glories of dealing with inner pollution doesn't go down well. Everyone seems to be drinking much quicker than usual and laughing hysterically. Hah! At least I'll have Sunday morning without a hangover.
But the headache persists on Sunday. Obviously there are more toxins in my body than I thought. The vegetable soup is okay, but Vanessa's four- cheese pasta looks so good I have to stop myself lunging for it.
"How are you feeling?" she asks.
"Never better," I say through gritted teeth running carrots and beetroot through the juicer. A horrible disloyal thought went through my mind. I never want to see another beetroot as long as I live.
"I was reading your book," she says later that evening. "You know, you really should be doing this for 30 days if it's going to work."
A terrible vision swims through my unpolluted head. 30 days of anti-social behaviour just for a bit of glowing skin? I say nothing. But if you see a girl on the tube with a huge Danish pastry this morning you'll know who it is.