Glycaemic Index

Having a rapidly expanding waistline is bad enough; acquiring potentially lethal liver disease is even worse.

New research suggests you can get both by eating diets rich in rapidly digested carbohydrates - foods with a high glycaemic index, or "GI".

GI is rapidly becoming the new watchword of the diet conscious.

Numerous healthy GI dietary regimes have been worked out, and supermarkets are starting to put GI ratings on food labels.

High glycaemic foods are carbohydrates which are digested quickly and release their energy rapidly into the blood stream.

Examples include white rice, white bread, most prepared breakfast cereals, and concentrated sugar.

Low GI foods, such as most vegetables, fruits, beans and unprocessed grains, raise blood sugar more slowly.

Scientists compared the effect of both kinds of food on mice, which were fed on either a high or low-glycaemic form of cornstarch.

Each diet had equal amounts of total calories, fat, protein and carbohydrate.

After six months, the mice weighed the same. But while mice on the low-glycaemic diet were lean, those on the high-glycaemic diet had twice the normal amount of fat in their bodies, blood and livers.

The findings, reported in the journal Obesity, showed how energy-giving sugar released by high GI food drives up the production of insulin, which in turn tells the body to make and store fat.

The message is strongest in the liver, where insulin concentrations can be many times higher than in the rest of the body.

According to the mouse experiments, raised insulin levels caused by eating high-glycaemic foods can lead to a build-up of fat in the liver which might be severe enough to cause harm.

"Fatty liver" usually produces no symptoms, but it increases the risk of inflammation which can lead to hepatitis, liver failure and even death.

Dr David Ludwig, director of the Optimal Weight for Life programme at the Children's Hospital in Boston, US, who led the research, said fatty liver was becoming more common in America, especially among children.

Just one case of fatty liver in a child was reported in the US in 1980.

Today, between a quarter and half of all overweight American children are thought to have the condition.Many of these children will be at risk of full blown liver disease in later life, said Dr Ludwig.

"This is a silent but dangerous epidemic," he warned.

"Just as type 2 diabetes exploded into our consciousness in the 1990s, so we think fatty liver will in the coming decade."

Our experiment creates a very strong argument that a high-glycaemic index diet causes, and a low-glycaemic index diet prevents, fatty liver in humans."

He hoped a clinical trial just launched in Boston will confirm the findings, and offer proof that a low-glycaemic diet can reverse fatty liver in overweight children.

The study will focus on children and teenagers aged eight to 17 who will be randomly given either a low-glycaemic diet or a regular low-fat diet.

Fois gras - the French pate delicacy - is made from the fatty liver of a duck or goose that has been over-fed with high-glycaemic grains, Dr Ludwig pointed out.