Metabolic Syndrome

What is metabolic syndrome?
Who has metabolic syndrome?
How is metabolic syndrome diagnosed?
AHA recommendation for managing metabolic syndrome
Learn your risk of developing metabolic syndrome
View an animation about metabolic syndrome
Download a printable sheet about metabolic syndrome
AHA scientific statements on metabolic syndrome

What is metabolic syndrome?

Metabolic syndrome is when a person has a group of metabolic risk factors including:

Abdominal obesity (excessive fat tissue in and around the abdomen)
Blood fat disorders (mainly high triglycerides and low HDL cholesterol that foster plaque buildups in artery walls
Insulin resistance or glucose intolerance (the body can't properly use insulin or blood sugar)
Prothrombotic state (e.g., high fibrinogen or plasminogen activator inhibitor [-1] in the blood)
Raised blood pressure (130/85 mm Hg or higher)
Proinflammatory state (e.g., elevated high-sensitivity C-reactive protein in the blood)

The underlying causes of metabolic syndrome are overweight/obesity, physical inactivity and genetic factors. People with metabolic syndrome are at increased risk of coronary heart disease, other diseases related to plaque buildups in artery walls (e.g., stroke and peripheral vascular disease) and type 2 diabetes.

Metabolic syndrome has become increasingly common in the United States. It's estimated that about 47 million adults in the United States have it.

Obesity and insulin resistance are two potential and important causes of metabolic syndrome. Abdominal or central obesity (increased waist circumference) is the form of obesity strongly associated with metabolic syndrome. However, the mechanisms underlying the association between abdominal obesity and metabolic syndrome are not fully understood and likely are complex.

The syndrome is also closely associated with a generalized metabolic disorder called insulin resistance, in which the body can't use insulin efficiently. Some people are genetically predisposed to insulin resistance. Acquired factors, such as excess body fat and physical inactivity, can elicit insulin resistance and metabolic syndrome in these people. Most people with insulin resistance have central obesity. The biologic mechanisms at the molecular level between insulin resistance and metabolic risk factors aren't fully understood and appear to be complex.

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How is metabolic syndrome diagnosed?
There are no well-accepted criteria for diagnosing metabolic syndrome, but most doctors use the following criteria. The criteria proposed by the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) are the most current and widely used.

According to the ATP III criteria, metabolic syndrome is identified by the presence of three or more of these components:

Central obesity as measured by waist circumference:
- Men — Greater than 40 inches
- Women — Greater than 35 inches
Fasting blood triglycerides greater than or equal to 150 mg/dL
Blood HDL cholesterol:
- Men — Less than 40 mg/dL
- Women — Less than 50 mg/dL
Blood pressure greater than or equal to 130/85 mmHg
Fasting glucose greater than or equal to 100 mg/dL

The ATP III panel did not find evidence to recommend routine measurement of insulin resistance (e.g., increased fasting blood insulin), prothrombotic state or proinflammatory state.

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AHA recommendation for managing metabolic syndrome
More studies are needed to understand the relationship between metabolic risk factors and the efficacy of drug therapy in people who have the metabolic syndrome. Lifestyle interventions should be strongly considered for reducing cardiovascular risk. These include weight control, increased physical activity, and a diet designed to reduce risk for cardiovascular disease.

Other steps for managing metabolic syndrome are also important for patients and their doctors:

Routinely monitor body weight (especially the index for central obesity), blood glucose, lipoproteins and blood pressure.
Treat individual risk factors (hyperlipidemia, hypertension and high blood glucose) according to established guidelines.
Carefully choose anti-hypertensive drugs because different agents have different effects on insulin sensitivity.

This content is reviewed regularly. Last updated 02/16/09.