Experts believe excessive hormone levels may explain why small babies are at an increased risk of later developing heart disease

These babies, who grow quickly after birth, have already been found to be at greater risk of high blood pressure by the age of three, and to be overweight later in childhood.

Both are high risk factors for coronary heart disease and could become a "ticking time bomb" for health problems in adult life, say experts.

The British Heart Foundation (BHF) has put more than �45,000 into a study to find out if overactive hormone production is at the root of the problem.

This may lead to finding new ways to help prevent obesity and high blood pressure

Dr John Honour, lead researcher

Researchers at the University College of London (UCL) are looking at hormone production in the adrenal cortex.

This is part of the adrenal glands, which lie above the kidneys and manufacture hormones.

They think the body may have set the controls for these hormones both before birth and in early childhood.

Monitored since birth

The scientists will look specifically at cortisol, a hormone involved in response to stress, preventing inflammation and regulating the deposit of fat around the body.

Around 400 children aged eight will be studied who were part of the Avon Longitudinal Study of Parents and Children, the so-called Children of the 90s study.

The team will look at whether those who were smaller babies have different levels of cortisol which could lead to high blood pressure and obesity.

The children have been monitored since birth so scientists have data about their height, weight, waist and blood pressure from, when they were three, five and seven years old.

Dr John Honour, lead researcher for the project, said: "Our research has already shown that smaller babies develop blood pressure later and often have larger waist measurements.

"We hope to show that overactive production of adrenal steroids is linked to this problem.

"In the long term, this may lead to finding new ways to help prevent obesity and high blood pressure."

Prevention

Professor Sir Charles George, medical director at the BHF, said: "Levels of obesity in children have doubled, and even tripled in some age groups, since 1990.

"Both obesity and high blood pressure are major risk factors for CHD in later life.

"We look forward to seeing the results of this research which will hopefully find new ways to help prevent young people developing these serious health problems."