By Megan Lane
BBC News Magazine
London, UK
17 June, 2005

It's summer time, and thoughts turn to how to get into those swimming costumes in time for the holidays. The GI diet has toppled Atkins as the regimen of the moment - but can you still eat sandwiches for lunch?

Fruit is good. So too are salads, dark chocolate and grainy bread. Crisps are bad. Ditto beer, pasties and white baps.

These are the diktats of the GI - or Glycaemic Index - diet, which revolves around choosing low carbohydrate foods and lean meats. It was first touted quarter of a century ago as a way for diabetics to control their insulin levels, and has been popular in Australia for almost a decade.

In the UK, the GI diet hit the headlines briefly a few years back when long-time adherent Kylie's gold-hot pants became something of a tabloid obsession. But then we were a nation in thrall to the Atkins regime; not even the diet credited with sculpting Kylie's curves could tempt slimmers away from their steak sans frites.

Now in hype terms, Atkins has had the wind knocked from its sails, and the GI diet has stepped up to take its place. Books detailing low-GI recipes are storming the bestseller lists. Food ads and labels boast (sometimes spurious) GI claims. Porridge is on the breakfast menu in City take-out joints. And diet gurus and health professionals appear to be singing from the same hymn sheet in praise of GI.

Blood sugar

So how does it work?

The Glycaemic Index ranks carbohydrate foods from zero to 100 on the rate at which they raise blood glucose levels.

Low GI foods break down slowly and so raise blood sugar at a steady rate that sustains energy and helps you feel full for longer. High GI foods flood the body with sugar fast, but the effect wears off just as quickly. But these can have their place, for instance a banana or a glucose drink after strenuous exercise to replace blood sugar used during exertion.

The key to it all is insulin - low GI diets reduce insulin levels. For not only does this hormone stimulate fat production, it inhibits the breakdown of that fat. Too much insulin increases the risk of obesity, diabetes and high blood pressure - all health time bombs in industrialised countries.

"In theory the GI diet is quite easy - you eat low GI foods," says registered dietician Helen Stracey, of the British Dietetic Association. "But it can be complicated when you try to work out the GI value of a meal."

The diet allows three meals and three snacks every day - but the points for each food should be added up in order to stay within the daily limit, necessitating a meal plan. And healthy foods with a high GI rating, such as baked potatoes, can be offset with a topping of low GI baked beans.

Nor should foods be chosen on their GI rating alone; instead look at their overall nutritional value. The World Health Organization, which has given the thumbs-up to low-GI eating, agrees with this approach.

Ice cream, for instance, has a lower GI rating than watermelon. But it doesn't take an expert to work out that the former is loaded with fat and sugar, while the later is packed with vitamins A and C.

And no-carb foods like meat and cheese have a zero GI, regardless of how fat or salt-laden these might be. To be part of a healthy diet, it's best to choose leaner cuts of meat and lower fat dairy foods, says Mrs Stracey.

For those keen to keep their diet as natural as possible, GI has another drawback. Many GI gurus advocate the use of artificial sweeteners to satisfy that sweet tooth that is the downfall of so many dieters.

Food pyramid

But as far as fashionable diets go, this is seen as one of the better ones by health professionals. It reflects the old healthy eating "food pyramid" familiar from school days past.

Studies from the Harvard School of Public Health show that the risk of type 2 diabetes and heart disease are strongly linked to the GI of the overall diet. Last month, researchers at Hammersmith Hospitals NHS Trust found that eating just one extra low GI item per meal cut blood sugar levels.

"Were we pleased to see the back of the Atkins diet? Very much so," says Mrs Stracey.

"We don't really see GI as a fad diet; dieticians have been talking about it since the late 1980s. But no healthy eating plan is easy. People like to do something extreme for a short period of time to lose weight; and the problem with diets is human temptation."

One Amazon reviewer disappointed by her bestselling GI tome said there was nothing new she hadn't already been told at Weight Watchers. "If you stick to lean meat, lots of fruit and veg, no sugar and a limited amount of high-fibre carbs, then you'll already be on this diet (and pretty much every other diet that's been around for the past 20 years)."

Unfortunately it doesn't work for me. Anything other than high-fat Atkins gives me cravings, causes me to over-indulge in the wrong carbs, and make me depressed and lethargic.

Why would low GI also imply low fat I wonder?

What is so different about low GI and Atkins?

I've been pondering this for a year or so. I went on the "real" low GI (GL) diet but after reading all the books iI found I was also on the Atkin's maintenance and fifteen other diets. I think people need a new label and a new book to read.

1. because fat is BAD for you! Don't you read the "studies"?

2. There is no difference for carbs, but with Atkins you can eat the natural, healthy fats!

I've also seen this over and over again. Of course, the fact that Dr Atkinstalks about GI....well you won't know that if you don't read the book!

Fat is very low GI

Atkins bars are extremely low in GI. So if the GI diet works, we could have had better experience with them!

I know that eating low GI foods has some advantage but this advantage is never enough to allow an obese person to lose his weight and keep it off for life.

Fat has a glycemic index of pretty near zero.

Why it is limited on a low glycemic diet is, unfortunately, a mystery that only the highest priests of nutritional authority know the answer.