IDF definition of the metabolic syndrome: Frequently asked questions

1. What is the metabolic syndrome?

The metabolic syndrome is a cluster of the most dangerous heart attack risk factors: diabetes and prediabetes, abdominal obesity, changes in cholesterol and high blood pressure.  For a person to be defined as having the metabolic syndrome, the new definition requires they have central obesity, plus two of the following four additional factors: raised triglycerides (TG), reduced HDL-cholesterol, raised blood pressure or raised fasting plasma glucose level. Gender and, for the first time, ethnicity specific cut-off points for central obesity as measured by waist circumference are included.

2. What are the health implications of having the metabolic syndrome?

People with metabolic syndrome are at increased risk of cardiovascular disease, being twice as likely to die from, and three times as likely to have a heart attack or stroke compared to people without the syndrome. People with metabolic syndrome have a five fold greater risk of developing type 2 diabetes (if not already present), a condition which is strongly associated with cardiovascular disease, as up to 80 per cent of the almost 200 million adults globally with diabetes will die of cardiovascular disease. It is the exact nature of the cluster which appears to bring additional risk over and above that which would be expected from each of the components (high triglycerides when measuring cholesterol, for example). This puts metabolic syndrome and diabetes way ahead of HIV/AIDS in morbidity and mortality terms yet the problem is not as well recognized.

3. How common is the metabolic syndrome?

A quarter of the world’s adult population have metabolic syndrome and the condition increases in frequency with age. However, the condition is also afflicting an increasing number of children and adolescents as the worldwide epidemic of obesity spreads across the age groups.

4.  Why a new definition?

There was a need for a single, universally accepted diagnostic tool to address both clinical and research needs.  The new definition is easy to use in clinical practice. It avoids the need for measurements that may only be available in research settings. This tool enables clinicians to identify patients with metabolic syndrome in the practice setting more quickly. Early and aggressive action will inevitably reduce the increased risk to the patient of developing cardiovascular disease and/or type 2 diabetes. Put simply, we have the potential to stop the cardiovascular disease time bomb. In addition, the use of a single definition will make it possible to estimate the prevalence of metabolic syndrome and make comparisons between nations.

5. How is the metabolic syndrome treated?

The key to tackling the metabolic syndrome lies in a better understanding and early diagnosis and treatment of the metabolic syndrome. While no single treatment for the metabolic syndrome as a whole yet exists, we know that lifestyle changes form the underlying strategy of treatment.

Once a diagnosis of the metabolic syndrome is made, the future management of the condition should be aggressive and uncompromising in its aim to reduce the risk of cardiovascular disease and type 2 diabetes. Patients should undergo a full cardiovascular risk assessment (including smoking status) in conjunction with the following:

Primary intervention

IDF recommends that primary management for the metabolic syndrome is healthy lifestyle promotion. This includes:

  • moderate calorie restriction (to achieve a 5–10 per cent loss of body weight in the first year)
  • moderate increase in physical activity
  • change in dietary composition

Secondary intervention

In people for whom lifestyle change is not enough and who are considered to be at high risk for cardiovascular disease, drug therapy may be required to treat the metabolic syndrome. While there is a definite need for a treatment that can modulate the underlying mechanisms of the metabolic syndrome as a whole and thereby reduce the impact of all the risk factors and the long term metabolic and cardiovascular consequences, these mechanisms are currently unknown and specific pharmacological agents are therefore not yet available. It is currently necessary instead to treat the individual components of the syndrome in order that a reduction in the individual risk associated with each one will reduce the overall impact on cardiovascular disease and diabetes risk. However, new therapies are on the horizon which may address several of the risk factors concurrently and this may have a significant impact on reducing both cardiovascular and diabetes morbidity and mortality.

6. Has waist circumference been defined for different age groups?

The first IDF consensus worldwide definition established criteria to identify metabolic syndrome in adults. In the mean time, the IDF Task Force on Epidemiology and Prevention has established criteria to identify metabolic syndrome in children and adolescents.

7. Questions regarding Japanese data

The first IDF definition of metabolic syndrome, which was launched 2005, had a waist circumference for Japanese people that was different from the updated 2006 definition.

  • What were the references for the 2005 definition in Japanese women and men (the established cut-points were >85cm in men, >90cm in women)?

The values came from a report and based on data from Japan comparing computed abdominal tomography (CAT) and magnetic resonance imaging (MRI) to waist circumference. These are the official Japanese obesity figures. See: The Examination Committee of Criteria for ‘Obesity Disease’ in Japan, Japan Society for the Study of Obesity: New criteria for ‘obesity disease’ in Japan. Circulation Journal 2002; 66: 987-992.

  • Why were definition cut-points in Japanese women and men changed (to >90cm in men, >80cm in women)?

The official Japanese position is accurate if healthcare professionals and scientists only look at waist measurement as an accurate expression of visceral adiposity measured by computerized tomography. However, it would seem that revised Japanese values conforming with the rest of Asia best reflect the onset of risk factors such as heart disease and diabetes.

When the original IDF report was published, many people from around the world challenged the fact that the figures for Japan were significantly out of line with the rest of Asia, but they were the official Japanese obesity figures and remain the official Japanese policy as reported by the 'Committee to evaluate diagnostic standards for metabolic syndrome'.

However, there have been a number of recent publications which point out that the waist circumference figures for Japan, with respect to determining the risk of heart disease and diabetes, are similar to the rest of Asia.

On this basis, the IDF Task Force on Epidemiology and Prevention decided to deal with all of Asia in the same way until more data are available from other countries in the region. The Task Force intends to review all the data and information within the next 12 months to see what the final outcome would be. Computerized tomography is not always available, particularly in primary healthcare settings, and it may well be that within Japan there will be two positions depending on the availability of the technology.