Metabolic Syndrome

Metabolic Syndrome

Also called: CHAOS, Metabolic Syndrome X, Reavens Syndrome, Insulin Resistance Syndrome, Dysmetabolic Syndrome


Metabolic syndrome is the name given to a cluster of medical conditions that significantly increase an individual’s risk of developing type 2 diabetes and cardiovascular conditions, such as heart attack and stroke.

Definitions of metabolic syndrome vary. The National Institutes of Health and the American Heart Association describe it as the presence of at least three of the following conditions:

  • Abdominal obesity
  • High blood pressure
  • Insufficient HDL “good” cholesterol
  • Elevated triglycerides
  • Elevated fasting glucose (prediabetes)

Insulin resistance is also commonly included as one of the possible factors in metabolic syndrome.

The exact cause of metabolic syndrome is unknown. However, many researchers believe that insulin resistance, in addition to being a component, is a contributing factor, along with:

  • Age
  • Race
  • Weight 
  • History of diabetes
  • Other diseases

Because this condition is characterized by obesity, treatment generally includes weight loss, modifications to diet, exercise and, if necessary, medication.

About metabolic syndrome

Metabolic syndrome is not a disease. Rather, it is the name given to a collection of interrelated medical conditions that, together, drastically increase an individual’s risk of developing certain conditions, including:

  • Type 2 diabetes. A metabolic condition in which the body is unable to use insulin properly or does not produce enough of this glucose-regulating hormone.
  • Cardiovascular disease. A disease of the heart and blood vessels. In addition to raising the risk of heart conditions, metabolic syndrome can be a marker of undiagnosed atherosclerosis, even in apparently healthy young adults, according to recent research.
  • Stroke. An event in which the flow of oxygen to the brain is suddenly interrupted.
  • Fatty liver disease. A buildup of fat in the liver cells, which can lead to hepatitis and cirrhosis.

People with metabolic syndrome have a five-fold increased risk of developing type 2 diabetes (if not already present), three times the risk of heart or stroke, and double the risk of dying from heart attack or stroke, according to the International Diabetes Federation (IDF).

Because metabolic syndrome may develop long before these diseases materialize, identifying and treating this syndrome in its early stages can often help delay or prevent their onset.

Definitions of metabolic syndrome vary. The National Institutes of Health and the American Heart Association describe it as the presence of at least three of the following conditions:

  • Abdominal obesity
  • High blood pressure
  • Insufficient HDL  “good” cholesterol
  • Elevated triglycerides
  • Elevated fasting glucose (prediabetes)

The IDF in 2006 released a consensus statement describing metabolic syndrome as culturally defined central obesity (specifying waist circumference of at least 94 centimeters [37 inches] for European men, 90 centimeters [35 inches] for Asian men, and 80 centimeters [32 inches] for European and Asian women), along with two of the following four factors:

  • Elevated triglycerides: at least 150 milligrams per deciliter (mg/dL), or specific treatment for high triglycerides
  • Reduced HDL cholesterol: less than 40 mg/dL in men or 50 mg/dL in women, or specific treatment for low HDL
  • Raised blood pressure: systolic blood pressure of at least 130 millimeters of mercury (mm/Hg) or diastolic blood pressure of at least 85 mm/Hg, or treatment for previously diagnosed high blood pressure
  • Elevated fasting glucose: at least 100 mg/dL, or previously diagnosed type 2 diabetes

Insulin resistance, which is closely related to prediabetes, is also commonly included as one of the possible factors in metabolic syndrome. Other contributors may include high levels of LDL “bad” cholesterol or VLDL “very bad” cholesterol, inflammation (increased C-reactive protein in the blood) or prothrombotic state.

Metabolic syndrome may also be called metabolic syndrome X, insulin resistance syndrome, dysmetabolic syndrome and Reavens syndrome. It affects one-fourth of the world’s population, according to the IDF. Metabolic syndrome is so closely associated with type 2 diabetes that many experts question whether diabetes should be added to the cluster of disorders that defines the condition.

Individuals at risk of developing metabolic syndrome should consult their primary care physician, who may recommend scheduling an appointment with an endocrinologist, a physician who specializes in treating hormonal and metabolism disorders.

The American Diabetes Association and the European Association for the Study of Diabetes issued a joint statement in 2005 that questioned the definition and even the existence of metabolic syndrome. They stated that the combination of conditions may not increase risk of complications any more than if these conditions were considered separately. Until further research shows a need to do otherwise, physicians should treat a patient’s various conditions and symptoms rather than diagnosing and treating a separate disease, the organizations suggested.

However, the IDF continues to offer guidelines for diagnosing and treating metabolic syndrome. It suggests moderate calorie restriction, diet and exercise as the primary intervention, with medications as the secondary intervention if these methods fail.

Potential causes and risk factors

Many experts maintain that the conditions associated with metabolic syndrome are connected to one another. Though the exact cause of this syndrome is unknown, many researchers believe that resistance to insulin, a hormone produced by the pancreas to regulate glucose (blood sugar), is a major contributor.

The body relies on insulin to transport glucose from digested food into the cells where it is converted to energy. When the pancreas does not produce enough insulin, or the body is unable to take advantage of its insulin supply, glucose builds up in the bloodstream and cannot enter the cells to provide energy. This condition, known as insulin resistance, sets the stage for type 2 diabetes. For this reason, metabolic syndrome is often referred to as a prediabetic condition, where blood glucose levels are elevated but not yet high enough to be classified as diabetes. Treatments such as exercise and diet can help keep prediabetes from escalating to type 2 diabetes.

It is also believed that the following factors can significantly increase an individual’s risk of developing metabolic syndrome:

  • Weight. Several factors related to weight increase a person’s risk of developing metabolic syndrome:
    • Abdominal obesity (sometimes called a “beer belly,” “apple shape” or “central obesity”). Excess fat around the midsection, or a high waist-to-hip ratio. This is a crucial element of metabolic syndrome. Recent research suggests that the tendency to develop visceral fat starting in middle age may decrease levels of a hormone called adiponectin, which can help control levels of glucose and fat.
    • High body mass index (BMI). A BMI of 25 or greater.
    • Low birth weight. Although overnutrition (excess consumption of calories) after birth raises the risk of metabolic syndrome and type 2 diabetes, insufficient nutrition during fetal development also raises their risk, according to the International Diabetes Federation. 
  • Age. The risk of developing this condition increases with age. According to the American Heart Association (AHA), less than 7 percent of individuals in their 20s have metabolic syndrome, compared to more than 40 percent of individuals in their 60s. However, experts are noticing an increase in risk factors among school-age children, and the AHA estimates that 4 percent of adolescents ages 12 to 19 have metabolic syndrome.
  • Race. Risk also varies by racial or ethnic backgrounds. According to the AHA, Mexican Americans have the highest risk of metabolic syndrome (32 percent), followed by white Americans (23 percent), African Americans (22 percent) and “other” racial groups (20 percent). Though there is little difference seen between risks for men vs. women in general, differences are found within certain racial groups. Among African Americans, women have a 57 percent greater risk than men of developing metabolic syndrome. Among Mexican Americans, women have a 26 percent greater risk than men.
  • Medical history of diabetes. Individuals are more likely to develop metabolic syndrome if they have a family history of type 2 diabetes or previously had gestational diabetes, a condition that can occur only during pregnancy.
  • Other diseases. Several conditions can increase an individual’s risk of developing metabolic syndrome, including:
    • Polycystic ovarian syndrome. A disorder in which a woman has irregular menstrual cycles and produces extra male hormones.
    • Cardiovascular disease. Diseases of the heart and blood vessels.
    • Dyslipidemia. A condition characterized by any combination of high levels of “bad” LDL or “very bad” VLDL cholesterol, insufficient “good” HDL or elevated triglycerides.
  • High blood pressure. A condition in which blood pressure is higher than normal.
  • Gulf War syndrome. The National Health Survey of Gulf War Era Veterans and Their Families has found an elevated incidence of metabolic syndrome, chronic fatigue, joint pain and other disorders in veterans of the Persian Gulf War of 1991.
  • Sleep apnea. Recent research links this sleep disorder to increased risk of metabolic syndrome, insulin resistance and type 2 diabetes.
  • Genetics. Scientists recently found that damage to a gene involved in repairing DNA (the NEIL1 gene) may increase the risk of metabolic syndrome.
  • Stress. Research indicates that chronic stress increases the risk of metabolic syndrome, heart conditions and type 2 diabetes.
  • Low testosterone. Several recent studies have linked low levels of testosterone (male hypogonadism), including that caused by androgen deprivation therapy for prostate cancer, to men’s risk of metabolic syndrome and insulin resistance, in addition to sexual dysfunction.

Individuals who have any of these risk factors are advised to consult their primary care physician or, if there are multiple risk factors, see an endocrinologist.

Signs and diagnosis of metabolic syndrome

Because metabolic syndrome is characterized by the presence of at least three distinct disorders, there are no symptoms specific to this condition. However, the National Cholesterol Education Program (NCEP) has instituted the following guidelines to assist physicians in diagnosing this syndrome:

  • Abdominal obesity. To qualify as a component of metabolic syndrome, a patient’s waist circumference must exceed 35 inches (88 centimeters [cm]) in women and 40 inches (102 cm) in men. Children require a waist circumference at or above the 90th percentile for age and gender.
  • High blood pressure. The patient’s blood pressure must be greater than 130/85 millimeters of mercury (mm/Hg) for a diagnosis of metabolic syndrome. Again, for children, blood pressures above the 90th percentile are needed to qualify.
  • Elevated levels of triglycerides. A fatty material that circulates through the blood or is stored as fat tissue. The patient’s triglycerides must be higher than 150 milligrams per deciliter (mg/dL) for adults and 110 mg/dL for children to qualify as a component of metabolic syndrome.
  • Low HDL (high-density lipoprotein) cholesterol. Commonly referred to as “good” cholesterol, HDLs travel freely throughout the bloodstream, helping to reduce “bad” LDL cholesterol and prevent heart disease. For a diagnosis of metabolic syndrome, the patient’s HDL level must be lower than 50 mg/dL in women and 40 mg/dL in men and children.
  • Elevated fasting glucose (blood sugar). The patient’s fasting glucose level must be at least 110 mg/dL (at least 100, according to the American Heart Association) for a diagnosis of metabolic syndrome (men, women and children).

The International Diabetes Federation has recently established slightly different criteria.

Some other conditions frequently accompany metabolic syndrome, but are not necessary to diagnose the syndrome. They include:

  • Microalbuminuria. Small amounts of a protein called albumin are found in the urine.
  • Hyperuricemia. A condition characterized by high levels of uric acid (an end product of metabolism) in the blood.
  • Increased levels of blood factors that promote clotting, including fibrinogen and plasminogen activator inhibitor-1 (PAI-1).

Additionally, individuals with metabolic syndrome may have one or more of the following conditions:

  • Type 2 diabetes. A metabolic condition in which the body is unable to use insulin properly.
  • Hyperinsulinemia. A condition characterized by abnormally high levels of insulin in the blood.
  • Hyperferremia. Excess iron in the blood, a risk factor for diabetes, heart attack and other conditions.

Diagnosis of metabolic syndrome requires a blood pressure reading, measurement of the waistline using a tape measure and measurement of body weight using a scale. Physicians may also perform a few simple blood tests to measure levels of:

  • Glucose
  • Insulin (a hormone that regulates glucose)
  • Cholesterol and triglycerides
  • Uric acid
  • Fibrinogen
  • PAI-1
  • Ferritin (iron)
  • Testosterone in men

Treatment and prevention of the syndrome

Preventing type 2 diabetes, heart attack and stroke is the primary goal of treating metabolic syndrome. To treat this condition effectively, physicians must address all of its individual components (e.g., obesity, high blood pressure, dyslipidemiaand insulin resistance) using a technique called multiple risk factor intervention. Multiple risk factor intervention allows physicians to address each discrete factor, without aggravating one condition for the sake of improving another.

For most individuals, treating metabolic syndrome can be accomplished through:

  • Weight loss. A modest loss of 10 pounds (4.5 kilograms) can make a difference in insulin resistance and high blood pressure.
  • Proper nutrition. Experts recommend a healthy, balanced diet with plenty of fiber-rich foods, such as beans, fruits, vegetables and whole grains. Research indicates that fiber and possibly calcium and vitamin D can help prevent metabolic syndrome.
  • Regular physical activity. Physicians generally suggest 30 minutes of daily aerobic activity (exercise that improves consumption of oxygen) such as walking, hiking and swimming. Individuals should get approval from their physician before starting an exercise program.
  • Stress management. In addition to aerobic exercise, methods such as yoga, tai chi, relaxation exercises, deep breathing, visualization and biofeedback can help people control stress.
  • Frequent communication with a physician. The physician may routinely monitor several factors to ensure that lifestyle modifications are effective, such as:
    • Weight
    • Blood pressure
    • Glucose (blood sugar)
    • Cholesterol
    • Ferritin (iron)

If exercise and dietary changes alone are unsuccessful in treating metabolic syndrome, physicians may prescribe the following medications:

  • Weight-loss drugs. When prescribed as part of a healthy weight-loss plan that also involves exercise and proper nutrition, certain weight-loss medications can be effective in treating metabolic syndrome.
  • Insulin sensitizers. Some patients may be prescribed certain medications, such as thiazolidinediones and biguanides, to help improve the metabolism of insulin, which is thought to play a significant role in the development of metabolic syndrome. These same antidiabetic agents are frequently prescribed to decrease insulin resistance in people with diabetes. 
  • Antihypertensives (medications to lower blood pressure). Certain medications (e.g., ACE inhibitors, calcium channel blockers, diuretics) may be helpful in treating metabolic syndrome.
  • Cholesterol medications. Patients may be prescribed medications such as fibrates, statins and niacin, which can improve cholesterol profiles and help control metabolic syndrome.
  • Aspirin. Physicians may recommend aspirin to reduce the risk of heart attack, a condition that can be caused by metabolic syndrome.

For patients who have excess iron in their blood, treatment may include regular or occasional removal of blood(phlebotomy). The procedure is similar to that used when people donate to a blood bank.

The same factors used to treat metabolic syndrome can often prevent or delay the condition. At-risk individuals can reduce the likelihood of developing the condition by eating properly, exercising regularly, maintaining a healthy body weight and taking medications as prescribed.

Those who smoke cigarettes should speak with their physician regarding developing a plan to quit smoking. Cigarette smoking can lead to insulin resistance, which is believed to be the primary contributor to this condition.

Data from the third National Health and Nutritional Examination Survey (NHANES) indicate that modest consumption of alcohol might reduce the risk of developing metabolic syndrome. Patients are advised to consult their physician on how much alcohol, if any, it is safe for them to drink.

Additionally, experts recommend that parents promote physical activity and monitor their children’s eating habits to help prevent the onset of obesity, type 2 diabetes and metabolic syndrome.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about metabolic syndrome:

  1. Do I have or am I at risk of developing metabolic syndrome?
  2. What diagnostic tests might I need to undergo, and what do they involve?
  3. What do my test results show?
  4. What are my treatment options?
  5. Can I avoid the need for medications by exercising more, improving my diet and quitting smoking?
  6. Will my conditions be treated with multiple risk factor intervention, so that the treatment of one condition does not worsen another?
  7. What tests do I need for monitoring, and how often?
  8. How is metabolic syndrome related to diabetes? Is my diabetes likely to cause metabolic syndrome, or is my metabolic syndrome likely to cause or complicate diabetes?
  9. What risks do I face if my metabolic syndrome is not controlled?
  10. Can I prevent metabolic syndrome?
Scroll to Top