Twenty four years later, the book has remained so successful that Eyton has rewritten it for a noughties audience to encompass modernday health and dieting issues.

The diet works on the premise that the more fibre you eat, the fuller you will feel . . . and the less likely you will be to snack and overindulge. It focuses strongly on "good elimination", which is the key to keeping the colon active and healthy . . . in fact, the F2 will discuss your colon and its contents in great detail and you will be working steadily towards the "perfect F2 poo" (which, by the way, is sausage or snake like, smooth and soft and should "glide out comfortably, without any straining". Those of you expelling little pony nuts should definitely read on! ) There's bad news for carnivores . . . a high-animal-protein and low-carb diet encourages bad bacterias to thrive in the colon whilst good bacterias love the conditions provided by a fibre-rich, plant-based diet. Studies by the International Agency for Research on Cancer show that a high intake of red meat and processed meat are associated with increased risk of colorectal cancer . . . so you won't find any steaks on the menu here. But, fuelled by Atkins-induced mania, the perception of daily requirements of protein has become distorted. "The problem with the modern diet, " says Eyton, "is the over-consumption of protein.

People have been following high-protein diets, but as the first-world's protein intake has gone up, so have the rates of diseases and cancers."

Whilst trying to lose weight, fat intake should be limited to 10 units a day (a unit is three grams). When you have reached your weight-loss goal, you can introduce more good fats into your diet and continue on the F2 for life-long maintenance. Good fats are polyunsaturated (included in oily fish, flaxseeds and walnuts and their oils, plus omega 3 freerange eggs). Monounsaturated fats are also good and they can be found in olive and rapeseed oil and avocados. Bad fats are saturated fats (dairy and meat products, coconut and palm oils) and transfats, which lurk in margarines and fat spreads and ready-made foods.

You might be wondering why, all of a sudden, carbs are de rigueur. Well the answer lies in 'slow release carbs' such pulses and grains which release sugar into the blood slowly, keeping you satisfied for longer. Foods that send your blood sugars rocketing include refined carbs such as white bread and cakes.

You will probably recognise this formula as the GI (Glycaemic Index) but Eyton says: "GI is a factor in diet, but not so much that people should think about it and attach a numerical system to it. If you are eating a high-fibre diet you are automatically looking after your GI."

She recommends these simple rules to a healthy GI:

>> Eat minimally ground grains: the less finely ground wholemeal breads slow the release of sugar into the bloodstream as well as speeding transit time in the colon.

>> Eat loads of legumes: beans, lentils, chickpeas and peas are richly represented in F2 . . .

they have an exceptionally low GI and effectively lower the GI of meals.

>> Eat lots of fruit: People who eat three-four servings of high-fibre fruits such as blackberries, oranges, apples, pears, strawberries blueberries and plums have been found to have the lowest overall GI and the best bloodsugar control.

>> Eat plenty of pasta: wholemeal pasta has a low GI.

Case Study

The updated F2 Diet is so new that there are no case studies available yet, so I decided to give it two-week test run myself. I don't need to lose weight, but have a sweet tooth and can't help late-night snacking, which puts a strain on my digestive system and makes it hard for me to get up in the morning. I've increased my daily fibre intake, added All-Bran cereal into my diet, have cut down the protein portions and now cover my plate with vegetables and stick to 'good carbs' at mealtimes. I have cut out bad fats and only eat the good fats mentioned above. These were my findings:

>> The fibre is filling me up and I no longer even think about snacking in the evenings and inbetween meals . . . I'm too full.

>> I was very surprised to find that I don't crave sugary foods anymore.

>> My skin is clearer.

>> Waking up in the morning is easier (although I'm still working on that one! ) >> I have lost 2 lbs . . . even though I have not been dieting.

>> Sorry, but it has to be said that I have achieved the 'Perfect F2 Poo' which means that my colon is in good working order and is hosted by plenty of good bacteria.

>> There's no doubt about it . . . I'm going to continue.

The F2 Diet by Audrey Eyton is published by Bantam Press, 18.95 ONE DAY'S SAMPLE MENU Breakfast: Half a grapefruit; a high fibre, wheat-based cereal served with soya or skimmed milk; a sliced greenish banana and a sprinkling of sultanas or other dried fruit.

Anytime: One of the recommended low-fat or probiotic yoghurts.

Lunch: Large bowl of F2 soup (there are lots of recipes to choose from) with two slices of wholemeal toast, each spread with two tsp of low-fat hummus topped with halved cherry tomatoes if required; an apple, pear or orange.

Evening meal: Wholewheat pasta with homemade tomato sauce or chilled supermarket bought sauce: amatriciana, arrabiata or Napolitana; side servings of a green salad and an F2 salad (lots of recipes to choose from); serving of vanilla ice cream . . .not Cornish or luxury . . . with raspberries, strawberries or blueberries.