You want to watch your weight and eat well. What could be easier than having three gourmet meals delivered to your door each day? Clare Rudebeck tests the latest Hollywood diet to arrive in Britain

They arrive in the middle of the night, and are deposited on selected doorsteps across New York and Los Angeles. Small, black and stylish, these discreet cooler bags are packed with all the food a busy girl needs for the day: breakfast, lunch, dinner, and two snacks.

They arrive in the middle of the night, and are deposited on selected doorsteps across New York and Los Angeles. Small, black and stylish, these discreet cooler bags are packed with all the food a busy girl needs for the day: breakfast, lunch, dinner, and two snacks.

Invented by a gym owner from Long Island, who realised that there was a market for an idiot-proof diet among his cash-rich, time-poor clients, the Zone Gourmet service is arguably the world's most exclusive diet. Stars such as Brad Pitt, Cindy Crawford and Winona Ryder already shell out $37 per day for their doggy bags. And no wonder; there is no rule book, no calorie-counting and no cooking involved. You just eat what is in the bag and get on with the job of looking superhuman.

Just like Winona, I seem ideally suited to the service. Not only am I a disaster in the kitchen, but I also want to look like a film star. So I am glad to hear that the idea has finally made it to Britain. Pure Package now delivers its food parcels to desirable addresses across London - and mine is one of the first on its list.

The Consultation

Before I get the food, however, Pip Hartnall, Pure Package's nutritional therapist, calls me for a consultation. She has heard all the foody sins of its rich and famous clients, but is, unfortunately, far too discreet to reveal them. All she can tell me is that Patsy Kensit is a customer, and that many of her transatlantic clients do Zone Perfect in New York, four days a week, and Pure Package in London three days a week. I've never been to New York, but make a mental note just in case.

It transpires that, unlike its American cousin, Pure Package is not well-presented food deprivation, but the kind of diet you love to eat - healthy, ethical, fruity, diverse - if only you could manage to wean yourself off toast. Pip promises that it will help me to lose weight, boost my energy levels, and, most importantly, fill me up. It sounds like my kind of diet (except for the fact that it costs £27 per day).

First, we have to sort out how my little black bag is going to be delivered. Pure Package delivers between midnight and 5am, in case you start work at the crack of dawn. Unfortunately, there is nowhere safe to leave food outside my flat in the middle of the night. "You don't have a night porter?" asks Pip. I don't. I do, however, have a flatmate who frequently stumbles home in the early hours of the morning. We decide that it would probably be safer if it was delivered to the office.

As we speak, I'm sipping a Lemsip. I've had a raging cold for a week and, as I explain to Pip, I've had to employ all my tried-and-tested remedies - pizza, curry and plenty of cake - in order to stave it off. Pip points out that this is unlikely to have enhanced my immune system. But is pretty sure that five days on the Pure Package will get me back on track. "After five days, people say that they just feel lighter - less bloated," says Pip, "and that they are better at getting up in the morning. You may even lose some weight." Sounds perfect. By the weekend, I should be enjoying a standard of living previously reserved for American sitcom stars.

Day One

I arrive at work early, proceed to the post room, demand my package and run upstairs to rip it open. Clearly, eating breakfast at 10am is going to take some getting used to. Pip has assured me that I will not starve this week. But in a society where salad is seen as a viable meal option, you can never be too sure. I'm relieved to discover that I will be stuffing my face today. Lunch is a seared bluefin-tuna salade niçoise; while, for dinner, I can look forward to corn-fed chicken with sage, mushroom, bacon and roasted root vegetables. My three main meals, plus two snacks are packed neatly into the cooler bag, as if by a mother who believes me incapable of buying a sandwich without her. Each meal is clearly labelled and there is also a personalised menu in case I get confused.

It sounds idiot-proof, but, in my desperation, I eat my breakfast (a courgette- and-basil frittata) before reading the clear instructions to warm it up. Still, it is not bad at all cold, and my lunch is even better. That evening, I'm going round to my boyfriend's for dinner. He offers to cook, but I say that I'm bringing my own dinner. Watching him tuck into fish fingers and peas, while I enjoy corn-fed chicken, it's not hard to feel that Pure Package has its advantages.

Day Two

Unable to face the prospect of fasting until 10am, I have saved two slivers of butternut pumpkin from last night's dinner to eat before leaving for work. Some would call this cheating; I call it bending the rules slightly to avoid Tube rage. An hour later, I am tapping pitifully at the post-room window, demanding my food parcel. Both my boyfriend and the post-room boys seem to find my desperation due to minor food-deprivation highly amusing. Personally, I just feel like crap.

Breakfast, shovelled down at my desk, is fresh berries, natural yoghurt and organic muesli. It is absolutely delicious, although it seems that the demonisation of complex carbohydrates has even got to the chefs at Pure Package. You would be embarrassed to present a hamster with the sprinkling of muesli to be found at the bottom of my plastic tray. I move straight on to my morning snack: a Florelle pear and walnuts. Luckily, there's only an hour to go before lunch.

It's mid-afternoon and it's like a pressure- cooker in the office. I need chocolate: succulent, pep-you-up-and-inspire-you-to-be-able-to-write-anything chocolate. However, my afternoon snack is Cheddar and oatcakes. I eat it all, including the rind. By 8.30pm, I'm still at work fighting the urge to eat the pan-seared halibut with tagine of vegetables and herbed couscous sitting in its case beside my left ankle. I resist. Back home, at 9.30pm, I enjoy the best TV dinner of my life.

Day Three

I arrive at work an hour and a half before everyone else, and wrestle open my breakfast. Now I know what Pip meant about getting out of bed more quickly in the mornings. The promise of food doesn't half motivate you to get to the office. It may be something employers should consider for recalcitrant staff.

This doesn't upset me for long, however, because my morning snack is the undisputed highlight of the diet so far: an organic cinnamon and apple muffin. It is a cake and, what is more, it is not one of those diet cakes that looks like the real thing but tastes like a bathroom sponge. It is the genuine article and I savour it for as long as possible. In fact, I am beginning to feel altogether great. I have loads of energy and rattle through my work.

Tonight, I'm going out for a meal with a friend, which requires some detailed planning. When you're on the Pure Package, you cannot just turn up at a restaurant. Instead, you ask your chosen eaterie to fax Pip its menu and then she chooses your dinner for you. It's a bit like having an overbearing boyfriend who really does know what is best for you. I'm having tapas, and Pip suggests that I order one selection of olives, one salad, one vegetarian dish, and one meat or fish dish.

I'm delighted and head off into town with no chocolate cravings, no sluggishness and no doubt that I will have a yummy dinner. Unfortunately, when we turn up at the restaurant, we are told that we will have to wait an hour for a table. My resolve is pronounced missing and, 10 minutes later, I binge on a cheeseburger next door.

Day Four

I arrive at work, guilt-tinged. Is that bloating in my gut, or just an undigested burger? However, I forget about all that as soon as I look at my menu for the day. After breakfasting on a mouth-watering trio of soufflé omelettes, I look forward to my organic cinnamon and apple muffin, which is back for an unexpected but welcome encore. At 11.30am, however, I discover that I have been fooled by a typing error. Someone must have forgotten to update the menu: my morning snack is a pineapple and papaya.

Not that I mind, because this afternoon's snack turns out to be a bar of Green & Black's organic dark chocolate. This really is my kind of diet. What is more, I notice that lunch will feature crisp slices of lightly smoked ham direct from Corsica, and I have always felt that prosciutto trumps every conceivable argument for vegetarianism. The day just whizzes past, and before long, I am tucking into some tasty cumin-marinated lamb brochettes.

Day Five

It's Saturday, and so I have asked for my food parcel to be dropped outside my boyfriend's flat. Waking at 11am, I wander into the drizzle outside in my dressing-gown to retrieve it. However, on one sleepy inspection, it doesn't seem to be there. I return upstairs, convinced that one of the flats' other inhabitants has probably reported the package and had my breakfast blown up by a bomb-disposal squad. Doubtful of my theory, my boyfriend persuades me to have another look. I find the cooler bag.

Fortified with my breakfast of muesli with stonefruit compote, I head home. I'm having friends round for dinner, and one of the only things I can make is lasagne, so I decide to make that. I, on the other hand, will be eating sausage, braised cabbage and potato. Mashing the lumps out of the white sauce, I realise that I'm in a rather delicate position. My guests may reasonably wonder why they have to eat my cooking, but I don't.

My dinner guests arrive, curious to discover how close a resemblance my culinary efforts will bear to lasagne. They are pleasantly surprised. And as I spoon my sausage and mash out of its container and shove it in the microwave, I reflect that I may feel healthier, but my friends all think I'm barmy.

The conclusion

After five days, I still haven't turned into a superwoman. I was hoping for comparisons to Uma Thurman or Courteney Cox Arquette, but instead, my friends have looked on bemused as I have battled to stay Pure. However, there are consolations. As Pip promised, I do feel lighter, more energetic, less bloated. And, most importantly, I haven't had to eat my own cooking.