Forget the bathroom scales and get out the tape measure!

A new study has found that waist measurements are a better indicator of cardiovascular disease (CVD) than body mass index (BMI).

The results from the first large scale international study assessing prevalence of abdominal obesity (excess fat around the middle), in over 170,000 people, has confirmed that a high waist circumference is associated with CVD independently of BMI and age.

The International Day for the Evaluation of Abdominal Obesity (IDEA) study, involved a random sample of more than 6,000 family doctors in 63 countries, who measured the waists of all patients who consulted them on two half-days and took a detailed medical history.

The results showed that abdominal obesity is highly prevalent worldwide.

So it appears that a tape measure is a better tool in beating heart disease than a set of bathroom scales.

Experts have always thought that the more weight a person gains the higher their risk of a heart attack, but this study shows waist circumference matters more than weight.

The study found that in men, the risk of heart disease increased by between 21 and 40 per cent for every 14cm (5.5in) increase in waist size.

In women, the same increase in heart disease risk occurred for every 14.9cm growth in waist size.

These risks were consistent across all populations, despite the widely varying waist sizes among the 168,000 people who took part.

The researchers say that body mass index, which is established as an indicator of a person's vulnerability to heart disease, does not take into account the wide variation in the shape of individuals and populations.

They say the type of fat and where it accumulates is more important than the amount.

Excess weight around the stomach is more harmful in other parts of the body, such as the legs and hips.

The researchers say that fat deposited deep inside the abdomen, which is seen in an expanding waist, secretes toxins into the bloodstream, raises cholesterol and increases the body's resistance to insulin, essential for controlling blood sugar.

A rise in insulin resistance means the pancreas has to produce extra insulin, which can damage other organs, such as the kidneys.

Steve Haffner, M.D.,professor of medicine at the University of Texas Health Science Center in San Antonio, Texas, and member of the IDEA Study Executive Committee, says the IDEA study confirms the importance of measuring waist circumference, alongside current measures such as BMI, blood pressure, blood glucose and lipid levels, in identifying patients in a primary care setting who are at increased cardiometabolic risk.