By Clare Murphy

Health reporter, BBC News



Cake maker Mr Kipling's at it, and so is a growing section of the food industry.

Mushrooms have a protein which tastes just like oil

Transforming the constitution of food, or "reformulating" as it is known, is increasingly seen as a key plank in the campaign against obesity. If we can't give up the cakes, the cakes will have to change, the thinking goes.

Industry is starting to move relatively quickly on this front: keen to respond to changing consumer demands for "healthier" products and to protect itself from allegations of fuelling fatness.

At one end of the spectrum, companies are quite simply cutting the amount of unhealthy saturated fats in their food: Walker's Crisps for instance was lauded for starting to cook its crisps in sunseed oil instead of standard cooking fat, slashing the saturated content.

But at the other end, researchers are formulating products which the body processes in quite different ways, taking longer to digest and so keeping you full for longer.

Plus and minus

Taking fat or sugar out of food is not necessarily as straightforward as it sounds.

The product may simply not sit together properly - it is hard for instance to make ice cream bind without sugar, or pastry and chocolate without certain quantities of fat.

REFORMULATED PRODUCTS INCLUDE: Cakes Chips Butter Crisps Soft drinks Cheeses

Obesity 'not individuals' fault'

And rather than making it healthy, you could actually make it positively dangerous, the Food Standards Agency warns.

Taking too much saturated fat out of meat pies for example can affect the way the water reacts with the meat, and increase the risk of food poisoning. The same is true of cake mixture.

Take too much fat out of cheese and it won't do the things that consumers like it to do, such as bubble, melt and go brown.

Worst of all, it may end up not tasting like cheese, and researchers are agreed that if these products are to work, and genuinely reduce the nation's waistlines, they must be virtually indistinguishable from that which they are supposed to emulate.

Tastes like butter

Premier Foods, which makes Mr Kipling new reduced fat cakes, has its own laboratory working out the science behind reformatting foods.

But the public sector is also heavily involved. The Formulation Engineering Research Centre at the University of Birmingham has been looking at how you replicate the taste and texture of fats.

One particularly promising avenue is the mushroom. It produces hydrophobins, air cells which protect the fungus from water, but which appear to have the same material properties as oil. And yet they have no calories.

Because there are no legal constraints around using mushroom extract in food - it is already widely available - this is an ingredient which could be "applied across the whole board very soon", said Professor Ian Norton.

"It would be suited to anything that is fabricated - mayonnaises, sauces, ice-creams, anything which has a fat content - the texture and taste would be the same and the calorie content dramatically reduced."

Little by little

But one of the long recognised problems of low-fat foods is how they are used: the fewer the calories, the more you can eat, the mantra goes for some. Others add so much sugar that the calorie content is ultimately not far off that which they were meant to replace.

Scientists are therefore looking into creating foods that actually change the way the stomach empties.

Adding components used in some acid reflux remedies is one option, as these appear to provide a barrier which slows the rate of digestion down.

But there may be limits to how much the consumer will stomach.

Alongside the increasing demand for healthier options is a renewed emphasis on the "natural". This is thought to explain a rise in butter sales in recent years over those of margarine, seen by many as a "chemical" product.

Reformulated food is in any case not the only answer to Britain's obesity woes.

"There's also a very important psychological issue too," says Professor Norton.

"Changing the food is only one part of it, you've got to change the whole range of attitudes towards food too."