The glycaemic index ranks the speed at which the body breaks down carbohydrates and converts them into blood glucose. Low GI foods, such as nuts, vegetables and bran-based cereals, are considered healthier for the heart than high GI foods like biscuits, white bread and sugar drinks as they are digested more slowly and as a result have a smaller impact on the body's peak blood glucose concentration.
Most of the research conducted into the glycaemic index has therefore concentrated on its effect on insulin sensitivity as a means to reduce the risk or control the management of diseases such as diabetes and heart disease.
But as the popularity of low-carbohydrate diets wanes, consumers in the UK are turning to the glycaemic index as a weight loss method. And with sweet and savoury pastries together with the large majority of bread types on the market ranked as high GI, the bakery industry may well be facing a new threat.
Unlike previously fashionable diets, use of the glycaemic index for weight loss has been led by retailers and the media rather than dieticians and food manufacturers. The promotion of the glycaemic index relies on a small but increasing collection of studies on the role of low-GI foods for weight management.
Some studies have revealed a significant effect on satiety and reduced body fat.
The UK's leading supermarket Tesco promotes a 'Tesco GI diet' on its website, providing information to consumers on how to "banish cravings, lose weight and improve health". Tesco also sells a booklet explaining GI, and has included 'low-GI' or 'medium-GI' labels on some of its products.
The consumer media has also compared a low GI diet favourably with Atkins, suggesting that it has sound scientific backing and proven benefits.
But Professor Tom Sanders from King's College London believes that while there is scope for the development of a GI diet, more research needs to be undertaken before its potential benefits can be confirmed.
"I remain skeptical for the broader use of the GI as a weight-loss diet label. A low GI diet is extremely hard to adhere to, and there have not been sufficiently large or controlled studies in free living individuals in order to promote its use," he told BakeryAndSnacks.com.
Dr Tamara de Grassi, nutritionist and head of communications at the UK's Flour Advisory Bureau (FAB), adds that the hype surrounding low GI foods "is all about making money."
"The people marketing GI are very canny. If we hadn't had Atkins and the whole debate on no-carb and low-carb, we wouldn't now be talking about right-carb, " she said.
Furthermore the glycaemic index is difficult for consumers to understand and can be misleading as GI levels can change depending on what combinations food is eaten in, how much it is chewed and how fast it is eaten. "Consumers don't have enough information or background knowledge to understand the complexities and the real facts about GI… without the right understanding they could end up with a disproportionate diet," added Dr de Grassi.
Research carried out by Leatherhead Food confirms that although one third of consumers are aware of the GI system, most are unable to interpret the often complicated labeling on products.
Yet a number of food manufacturers are now forging ahead with new marketing initiatives to promote and explain the benefits of their low-GI products.
Danone has labelled a number of its products on the Dutch and French markets with the label 'longer lasting energy', using charts to show the effects on blood sugar. Meanwhile ingredient makers Danisco, Sensus and Tate & Lyle are positioning products around this new market.
If new science continues to support the role of the glycaemic index in weight loss, the bakery sector may need to follow Warburton's lead. The UK firm has been one of the first to anticipate the impact of this emerging trend by developing a white bread with a low GI, backed by a £2m advertising campaign.