PAUL McKenna can make you thin.

Gillian McKeith makes the aduki bean your best friend. The Food Doctor, meanwhile, will change the way you eat forever.

And so on. Our expectations of diet books are no higher than that they give us the desired result. We don't predict that we'll have a lot of fun along the way, either reading the book or following the diet itself.

Then along comes Neris and India's IdiotProof Diet: How we lost ten stone (they wanted to call it From Pig to Twig). This is a notable deviation from the usual weightloss book, by virtue of the fact that it's a hoot to read, throwing into sharp relief the relentlessly depressing tone of most other diet books. It's an amusing book that you wouldn't be mortified to be spotted reading on the Dart.

India is India Knight, a British journalist and novelist; Neris is Neris Thomas, a film producer and artist, and their book, based on their personal journeys from size 20 to size 14, looks like one of those guides to how to be a fabulous girl about town and reads like, well, one of Knight's witty and acutely observed columns.

That's not the only difference: their IdiotProof Diet is low on excessive exercise routines and strange foodstuff and high on looking at the real reasons why we overeat;

the joys of Marks & Spencer's Magic Knickers and guidance over dieters' usual P stumbling blocks like drinks parties and weddings. Breaking it down, it's a lowcarbohydrate/high-protein plan that fits in with real people's lives, and, keeping in line with all other diet books, if you follow it to the letter, they promise you'll see results and maybe even change your life.

The first and most important thing to point out is that neither Knight or Thomas have any expert credentials when it comes to dieting, unless one counts Thomas's two decades as a yo-yo dieter. Knight meanwhile, was a diet virgin and didn't own a scales until last summer. The book is not part of some branding exercise or moneymaking scheme and they promise that there are no plans for an exercise DVD.

"It was never my intention to write a diet book and I have a day job as a journalist and a novelist that I really enjoy so it's a onceoff, " Knight says. "I'm not Mother Teresa but it was done with an aspect of public spiritedness to it. It just seemed to Neris and I that we'd finally cracked this. There's a sea of diet books telling you to do all these conflicting things whereas actually, it's really straightforward. You eat in a particular way and you get your head around the problem and you can do it. That just seemed almost miraculous actually."

She points out that all diets work.

Anybody, she says, can lose weight but if it were only as simple as that, there would be no fat people. But very few diet books are written by formerly fat people. ("They're written by Rosemary Conley, who's only ever lost, I think a maximum of seven pounds?") unlike Knight and Thomas, who lost five stone each. "I can hardly pick up five stone now. When I went to the gym and tried to pick up the equivalent in pounds, I couldn't so I don't know how I was walking around with it. It makes you think about what it does to your heart, " Thomas says.

But it took a long, long time before Knight and Thomas addressed their weight problem seriously. The two have been close for many years, a friendship cemented by the fact that both have daughters with heart conditions and they were the only two women in their circle of friends who were the same size. "I didn't discuss diets with women before because I was so fat, " Knight says.

Their respective epiphanies came when they finally acknowledged how unhappy their weight was making them. Knight's happened around 2pm on 15 July 2005 in the what she calls "the fat person's department" (also known as 'relaxed clothing) in Selfridges when she experienced a huge rush of anger at what she'd done to herself - a woman entering her 40th year and weighing nearly 16 stone - and she decided that she'd had enough.

The lies she told herself throughout her decade of denial are categorised in the book accordingly: "Why don't M & S do bras in my size? The fools. Because there's a limit and 40H is probably it. At least I'm not some ghastly, neurotic, brittle anorexiclooking obsessive. Take me out to lunch, and I eat. True. But the choice isn't between looking like Victoria Beckham or Johnny Vegas. There is a middle way."

Thomas meanwhile, who had run the whole dieting gamut from the Oprah boot camp to fasting had also reached the end of her tether. The stress of her daughter being seriously ill had made her comfort-eat and she felt quite depressed in the aftermath.

She found herself making excuses to get out of meeting her husband's new colleagues because she feared she'd embarrass them.

She remembers how the idea to diet together kicked off. "I had come to the lunch with a GI diet book in my bag. I was looking at it, going, 'Am I really thick because I just don't understand this? I can't be bothered with it. It just doesn't talk to me.' I was just so confused and I felt like I'd reached diet saturation point. I said to India, 'If you tell me what to do I'll do it, but I need to do it with you and I need it to be really straightforward'."

Knight stocked up on diet books and did the homework. It became apparent to her that low-carb/high-protein was the way forward for serious weight-loss but they were too draconian for anybody trying to lead a normal live. "They'd be perfectly fine if you were a single person living on a desert island but if you have a family life or a social life then they're kind of impossible, " she explains. "Then, as we know, if something feels impossible you just get dispirited and give up and there you are, still fat."

Sugar in all its various permutations was banned from their kitchens and healthy fats, fish, organic meat and lots of water were embraced instead. Eating breakfast, lunch and dinner was a must, and while one will not go hungry on an eating plan that permits bacon and eggs in the morning, breaking the carb addiction was difficult for both. Until they started to read the labels, they were unaware of how frequently sugar is added to the most unlikely food stuffs, from ham to mayonnaise.

Treats like alcohol and chocolate are allowed in small quantities after a stricter two-week Phase One. The trickier aspect was coming to grips with why they overate.

Being happy, sad, bored, greedy or 'I'm already fat, so sod it anyway' thinking were all triggers and a substantial portion of the books looks at the psychology of why we get fat and how to retrain the brain.

After a month and a half, they were starting to see results and this was when the idea of doing the book came to them.

Just as their diet histories had contrasted, so do did their efforts at weight-loss. Knight found it relatively easy while Thomas struggled. She wasn't losing the amount that, in theory, she should have been and the reason was because she was cheating. She's a bit embarrassed at being ousted as a cheat in the book but says they promised to be honest. "I would have loved to have been the perfect school prefect type but unfortunately, I wasn't. We really wanted it to be warts-and-all and the important thing is that we got there in the end, " she says.

"Everybody takes their time to work out why they're fat in the first place and I took longer than India."

Some would call them brave. Did they think long and hard about writing what is such a self-revealing book? Possibly not long and hard enough, Thomas thinks.

Having been on a diet for most of her adult life, she'd never minded things like being weighed at WeightWatchers. She was also fired with enthusiasm for the project. "The main impetus was that we were really excited about the fact that it was working and we had each other, and we thought about this idea of it being a 'buddy book', it being your buddy. I think that all the previous times, I'd felt a bit lonely dieting and I felt there was something really missing then but I had it now so I felt somewhat evangelical. I felt like it was the right thing to do, " she recalls.

But she says that reading your own story back is "a weird one. Obviously, there were an awful lot of emotions involved which aren't necessarily attractive to read about yourself."

Knight's most difficult task was to stop being delusional about her appearance.

"You know the horrible pictures of us in leotards and tights?" she says. "That wasn't at our fattest. That was about a month and a half in, when we'd lost a stone, a stone and a half each by then. When we waddled out of the changing room in our tights and leotards, we actually didn't think we looked that bad and that is what remains completely amazing to me to this day. We thought we looked a bit tubby, but in a manageable, reasonable kind of way. I thought that about myself for about 10 years and suddenly, it wasn't pleasant suddenly realising that in fact, I was a complete blimp - the hardest thing was that it took a decade."

Writing this book hasn't made them poster girls for extreme weight-loss. They are both now a healthy size 14 and have no intention of losing any more weight. "There are people who want to be a size bloody zero - which is fine for them but which is mad - but for most women, it's about feeling healthy and okay about themselves, " Thomas says.

"I just want to wear alright clothes that I can choose and I just want to be healthy and that to me is about being about an average.

We are average, we're obviously not going to be stick-thin ever and if that comes across in the book, I'd be really pleased."

Knight says that prior to writing the book, she hadn't realised how unusual she was, as a female, in never having dieted before and has subsequently realised that every woman she knows, from her mother to people she says hello to on the street watch their weight. "It came as a complete revelation to me, " she says. Was she shocked? "I am quite shocked because I understand the need to do something about your weight if you're terribly overweight or terribly underweight but if you look great? then I suppose that is why they look great? but the obsessiveness is not good, the omnipresent obsessiveness is a bit disturbing I think."

Their book, they think, is a guide for life and should you ever feel like you're slipping, they say just pick it up and read it again.

Thomas says she's not on the diet at the moment and while she is always going to be greedy, she's confident that she now has a set of tools that she can use to work out why she overeats. Knight said that obviously she had bread sauce with her turkey and Christmas pudding over the holidays but she didn't go back for seconds and thirds, as she would have done in the past. "Now I've got it into my head in the way that I presume normal people have in their head all the time, that there are consequences to your actions and the consequences of having three helpings of Christmas pudding is that I'm going to put on some weight and I don't want to do that. I've grasped that now.

It sounds so simple when you articulate it but I only got there via an incredibly convoluted and long-drawn-out process."

CLEAR OUT YOUR KITCHEN

Give away the following or put them out of reach:

»All biscuits and chocolate bars
»Any cold drink that isn't water
»Any hot drink that isn't decaf tea or coffee, or herbal tea
»Anything containing sugar (check the label - the weirdest things contain sugar, like some jarred mayonnaise, and balsamic vinegar)
»All pasta
»All potatoes and potato-based products, including those containing potato flour (which is in many ready-meals)
»Any oil that isn't olive or groundnut
»Anything containing wheat (ie flour), whether it's sweet or savoury
»Any fruit (yes, we know. Fruit's supposedly good for you. But it's also full of sugar. Bear with us, it's only for two weeks)
»Any legumes. That means lentils, chickpeas and the like

IDIOT-PROOF RECIPES Roast Butternut Squash Soup with Parmesan and Bacon Piece of cake, this (well, not quite cake), and delicious.

One butternut squash Olive oil Vegetable or chicken stock (cubes are fine, Marigold is better) Parmesan cheese, grated Crispy bacon Cut the butternut squash in two lengthways. Brush it with olive oil and stick it in the oven, heated to 190ºC, gas 5, for an hour or so, depending on its size - it's ready when soft. Scoop out the flesh and whizz it in a blender. Put it in a pan with enough vegetable or chicken stock to achieve a consistency that's pleasing to you. Gently head through for 20 minutes or so. Serve with one big heaped tablespoon of Parmesan per bowl, and some crispy, crumbled bacon. Feel free to have seconds.

If you want to gild the lily, you could add some rosemary leaves to the roasting squash, and/or drizzle the finished product with a little truffle oil.

Cauliflower Faux-mash We used to HATE cauliflower. Now, to us, cauliflower rocks. Please try this - it's fantastic.

Half a cauliflower Butter Double cream Salt and pepper Nutmeg, if you like Steam the cauliflower florets until very tender. Chuck into a blender. Blend with a generous knob of butter and a glug of cream. Season. Serve. (Use any leftovers for fried mash cakes for tomorrow's breakfast. ) Tarragon Chicken One organic chicken breast per person, more if you're starving One bunch of fresh tarragon One small pot of double cream Butter Groundnut oil Half a lemon Cut the chicken into strips, or chunks if you prefer. Melt the butter in the pan on medium heat and add a tiny blob of groundnut oil. When it's sizzling, add the tarragon and the chicken strips, and cook the strips until they go crispy and brown (if crispy and brown and a bit sticky is what you like. I know I do).

Add enough cream to make a sauce - a third to half of the small tub should do it. Wait a minute for all to meld and bubble. Add the juice from the lemon, taste, and season if you think it needs it. Eat with the mash. Drink your water.

'Neris and India's Idiot-Proof Diet: How We Lost 10 Stone' (Fig Tree) is out now. Visit their website www. pig2twig. co. uk