Never mind calories – think GI

Whether you want to lose weight or just feel healthier and calmer, the glycaemic index is the new big thing in diets. Kylie swears by it. And Annalisa Barbieri is a GI convert, too

Between the time I left home, aged 22, and 14 years later, things went rather awry. Portions got bigger; meals became less balanced because of busyness; I could afford to eat out more, so I did... It's a familiar story that ended up with me eventually weighing somewhat more than I did when I left home. Not only this, but eating was no longer the simple pastime it used to be. I veered between feeling so hungry I thought I would faint, to feeling so full I would have to walk around the table clutching the backs of chairs.

Between the time I left home, aged 22, and 14 years later, things went rather awry. Portions got bigger; meals became less balanced because of busyness; I could afford to eat out more, so I did... It's a familiar story that ended up with me eventually weighing somewhat more than I did when I left home. Not only this, but eating was no longer the simple pastime it used to be. I veered between feeling so hungry I thought I would faint, to feeling so full I would have to walk around the table clutching the backs of chairs.

These extremes would mean that I would make bad choices in what I ate. "This is a common problem today," says Dr Wendy Doyle of the British Dietetic Association. "People don't plan ahead, then they get hungry and grab something really quick." It also meant that I had what I came to call my low blood-sugar level tantrums (madness for short) when I regressed to being a petulant child if I was hungry. My stomach was always bloated, my periods were haywire. It sounds dramatic, but it all came on so slowly that I put it down to just one of those things that happen as you get older.

However, in true western style, I was more concerned with losing the weight than addressing any of those other problems. And to do this I had to be humble and realise that I had to Do Something Different. I hated diets, the thought of diets, people on diets. But still, here I was weighing what I should weigh if I were on the scales holding a toddler. So, I decided to approach the problem scientifically, because I realised that I had no idea, not really, of the nutritional content of my food. Food had, over the years, simply become food that made me feel virtuous or guilty. Nutrition tables on the back of packets were only checked for the fat and calorie count. Wasn't that all that mattered?

Apparently not. The buzz word in weight loss now was "low-carb". Fat was no longer the big enemy; carbohydrates, or rather what the body breaks them down into – sugars – were. This is because, so the theory in the low-carb diet books goes, energy not used from sugar is stored as fat more readily than that from protein or even fat itself.

But in researching these diets, I came upon something else that was to make the hugest difference to the way I ate. The glycaemic index (GI).

The glycaemic index (I warn you, GI diets will be the new craze of 2002 – Kylie already follows a low GI diet) was developed 22 years ago by a professor of nutrition at the university of Toronto. It is a system of working out how quickly carbohydrates are broken down, digested and raise blood-sugar levels and thereby stimulate insulin production (insulin is produced by the pancreas to bring blood-sugar levels down again). The ratings range from 1 to 100 (100 is glucose), and this is where the big surprises come in. Anything below 55 is considered low, and will give you a slow, steady rise in blood sugar; between 55-70 is intermediate; above 70 is high and you'll probably feel full very quickly and then crashingly hungry again (sound familiar?).

It's probably not a surprise to learn that jelly beans have a GI of 80. But guess what has a GI of 76? Brown rice. In essence, this is why those low-carb diets tell you not to eat bread, rice, pasta or potatoes. (Actually, it is incorrect to lump pasta in with these, if pasta is made from semolina, it has a low GI because semolina is made from large particles of cracked-wheat endosperm that are digested more slowly. Basmati rice, too, has a low GI because of the structure of its starch. No one ever said this was going to be easy...)

Professor Jennie Brand Miller from the University of Sydney is a world authority on the glycaemic index, and author of 150 books on the subject. "Carbohydrate stimulates the secretion of insulin more than any other component of food," she says. However, Brand Miller is not a low-carb pusher; she advocates a high-carb diet, saying that at least 50 per cent of our energy should come from carbohydrates. But it's the type of carbs that matter.

"For over 10,000 years, our ancestors survived on a high-carbohydrate, low-fat diet. They ate their carbs in the form of beans, vegetables and whole cereal grains. They ate their sugars in fibrous fruits and berries. The result was that all food was digested and absorbed slowly and the usual blood-sugar rise was gradual and prolonged. This was ideal because it provided slow-release energy that helped to delay hunger and was kind to the pancreas."

Fat and/or protein will slow down the absorption of an otherwise high-GI food. That is why a potato crisp has a GI of 54 but potatoes generally (depending on type) have a high GI: a baked potato is 85.

You can see how the GI could become the new calorie-counter, but it should be used in conjunction with other nutritional data because being "low GI" does not necessarily mean a food is healthy in other ways. M&Ms, for example, because of the fat content, have a GI of 33, a Snickers bar 41. You can also find out the GI of foodstuffs by visiting the University of Sydney's GI database at www.glycemicindex.com – note the different spelling.

I looked at my diet: toast for breakfast, sandwiches for lunch, pasta for dinner, or, sometimes, if I needed real comfort, just a plate of lovely mashed potato, sometimes chips, sometimes a bowl of cornflakes. By just about any expert's reckoning (other research shows that our ancestors further back than "10,000 years ago", ate a diet rich in protein and fat), it was not great. I looked at official figures that told me we all ate too much fat, more protein than we needed and not enough carbohydrates. Despite all the food stuff I was eating also containing protein to some extent, personally I felt I wasn't getting enough protein and I was eating too much in the way of "easy" carbs.

After consulting a nutritionist, and taking the bits from various expert research that I knew would work for me, I decided that every meal or snack I ate should contain a balance of good fat, good protein and good carbohydrates. I now eat (I know, I've turned into a diet bore...) a very healthy diet during the week. I no longer think in terms of calorific values but rather in nutritional and GI ones. This means loads of veg, olive oil, white fish, oily fish, chicken, nuts, seeds and God's own food: porridge. It means no potatoes, pasta, rice and only one slice of wholemeal bread a day. Because – despite the low GI of pasta – it's easy for me to overeat these foods, they slip down so fast, whereas veg take longer for me to eat and digest. I rarely feel really full, but I rarely feel really hungry either.

I plan what I will eat, which, while not being very rock'n'roll, makes me feel a whole lot better: my blood-sugar levels are now so under control that I can wait and eat properly, which, for me, was the turning point (although, as I write, I've just finished my "36 hours off", during which I drank a lot, and alcohol plays havoc with blood-sugar levels, so until it's under control again, I'm back to being all over the place). For several reasons (mainly because banning anything would drive me insane) I have 36 hours a week off when I can eat what I want. Well, what's the point of an eating plan if you can't sustain it?

Coincidence or not, my stomach is flatter than it has ever been before. My periods are back to what they were 10 years ago. As Dr Doyle says: "Our hormones are affected by nutritional intake and your food probably has a lot more nutritional density to it now." And yes, I'm losing weight.

According to the Food Standards Agency, there are no plans to put the GI rating on food any time soon. This is a shame because the GI rating can be a useful tool. As long as we don't use it as another stick with which to beat ourselves.