More than 300 million people world-wide are unaware they have conditions that could lead to heart disease and diabetes, experts have warned.

The International Diabetes Federation (IDF) says millions have a condition known as impaired glucose tolerance (IGT) or the closely related impaired fasting glucose (IFG).

Diabetes is the biggest epidemic the world will face in this century so attacking it at the prediabetes stage is the most sensible strategy

Professor Paul Zimmet

The conditions, often referred to as "pre-diabetes", are an indication that the body is not breaking down sugars in the way it should. If untreated they can lead to serious health problems.

The IDF is calling for urgent international action to raise awareness of these conditions.

It recommends the introduction of screening programmes to identify those at risk.

IGT and IFG are more likely to be found in people with:

• a family history of diabetes
• obesity
• high blood pressure
• high cholesterol

They are also more likely to occur in certain communities, such as Asian Indians, Chinese, Pacific Islanders, indigenous Australians and Middle East communities.

Professor Paul Zimmet, director of the International Diabetes Institute in Melbourne, said people are generally not aware of the fact they have the conditions because there are no obvious symptoms.

Widespread problem

He said a recent Australian study showed that 16.3% of the adult population of the country had either IGT or IFG.

Over 50% of these people will develop diabetes within five years.

However, the risk of developing diabetes can be significantly reduced by intensive weight reduction and exercise.

In addition, the use of two diabetes drugs, metformin and acarbose, can prevent the development of diabetes in IGT patients.

Professor Zimmet said: "Diabetes is the biggest epidemic the world will face in this century so attacking it at the prediabetes stage is the most sensible and cost-effective strategy.

"We need more studies on lifestyle and drug intervention in people with IGT to reduce the massive burden that diabetes and cardiovascular disease place on our lives and our health systems."

People with IGT have blood glucose levels that are higher than normal but not high enough to say they have diabetes.

Three out of four people with diabetes die as a result of cardiovascular disease.

By the time Type 2 diabetes is diagnosed, 50% of people will already have cardiovascular and kidney complications.