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What Is Metabolic Syndrome?

Metabolic (met-ah-BOL-ik) syndrome is the name for a group of risk factors that raises your risk for heart disease and other health problems, such as diabetes and stroke.

The term "metabolic" refers to the biochemical processes involved in the body's normal functioning. Risk factors are traits, conditions, or habits that increase your chance of developing a disease.

In this article, "heart disease" refers to coronary heart disease (CHD). CHD is a condition in which a waxy substance called plaque (plak) builds up inside the coronary (heart) arteries.

Plaque hardens and narrows the arteries, reducing blood flow to your heart muscle. This can lead to chest pain, a heart attack, heart damage, or even death.

Metabolic Risk Factors

The five conditions described below are metabolic risk factors. You can have any one of these risk factors by itself, but they tend to occur together. You must have at least three metabolic risk factors to be diagnosed with metabolic syndrome.

  • A large waistline. This also is called abdominal obesity or "having an apple shape." Excess fat in the stomach area is a greater risk factor for heart disease than excess fat in other parts of the body, such as on the hips.
  • A high triglyceride level (or you're on medicine to treat high triglycerides). Triglycerides are a type of fat found in the blood.
  • A low HDL cholesterol level (or you're on medicine to treat low HDL cholesterol). HDL sometimes is called "good" cholesterol. This is because it helps remove cholesterol from your arteries. A low HDL cholesterol level raises your risk for heart disease.
  • High blood pressure (or you're on medicine to treat high blood pressure). Blood pressure is the force of blood pushing against the walls of your arteries as your heart pumps blood. If this pressure rises and stays high over time, it can damage your heart and lead to plaque buildup.
  • High fasting blood sugar (or you're on medicine to treat high blood sugar). Mildly high blood sugar may be an early sign of diabetes.

Overview

Your risk for heart disease, diabetes, and stroke increases with the number of metabolic risk factors you have. In general, a person who has metabolic syndrome is twice as likely to develop heart disease and five times as likely to develop diabetes as someone who doesn't have metabolic syndrome.

Other risk factors, besides those described above, also increase your risk for heart disease. For example, a high LDL cholesterol level and smoking are major risk factors for heart disease, but they aren't part of metabolic syndrome.

Having even one risk factor raises your risk for heart disease. You should try to control every risk factor you can to reduce your risk.

The risk of having metabolic syndrome is closely linked to overweight and obesity and a lack of physical activity. Insulin resistance also may increase your risk for metabolic syndrome.

Insulin resistance is a condition in which the body can't use its insulin properly. Insulin is a hormone that helps move blood sugar into cells where it's used for energy. Insulin resistance can lead to high blood sugar levels, and it's closely linked to overweight and obesity.

Genetics (ethnicity and family history) and older age are other factors that may play a role in causing metabolic syndrome.

Outlook

Metabolic syndrome is becoming more common due to a rise in obesity rates among adults. In the future, metabolic syndrome may overtake smoking as the leading risk factor for heart disease.

It is possible to prevent or delay metabolic syndrome, mainly with lifestyle changes. A healthy lifestyle is a lifelong commitment. Successfully controlling metabolic syndrome requires long-term effort and teamwork with your health care providers.




Other Names for Metabolic Syndrome

  • Dysmetabolic syndrome
  • Hypertriglyceridemic waist
  • Insulin resistance syndrome
  • Obesity syndrome
  • Syndrome X



What Causes Metabolic Syndrome?

Metabolic syndrome has several causes that act together. You can control some of the causes, such as overweight and obesity, an inactive lifestyle, and insulin resistance.

You can't control other factors that may play a role in causing metabolic syndrome, such as growing older. Your risk for metabolic syndrome increases with age.

You also can't control genetics (ethnicity and family history), which may play a role in causing the condition. For example, genetics can increase your risk for insulin resistance, which can lead to metabolic syndrome.

People who have metabolic syndrome often have two other conditions: excessive blood clotting and constant, low-grade inflammation throughout the body. Researchers don't know whether these conditions cause metabolic syndrome or worsen it.

Researchers continue to study conditions that may play a role in metabolic syndrome, such as:

  • A fatty liver (excess triglycerides and other fats in the liver)
  • Polycystic ovarian syndrome (a tendency to develop cysts on the ovaries)
  • Gallstones
  • Breathing problems during sleep (such as sleep apnea)



Who Is at Risk for Metabolic Syndrome?

People at greatest risk for metabolic syndrome have these underlying causes:

Some people are at risk for metabolic syndrome because they take medicines that cause weight gain or changes in blood pressure, blood cholesterol, and blood sugar levels.

These medicines most often are used to treat inflammation, allergies, HIV, and depression and other types of mental illness.

Populations Affected

Metabolic syndrome is more common in African American women and Mexican American women than in men of the same racial groups. The condition affects White women and men about equally.

Some racial and ethnic groups in the United States are at higher risk for metabolic syndrome than others. Mexican Americans have the highest rate of metabolic syndrome, followed by Whites and African Americans.

Worldwide, certain ethnic groups, such as South Asians, are at increased risk for metabolic syndrome.

Other groups at increased risk for metabolic syndrome include:

  • People who have a sibling or parent who has diabetes
  • People who have a personal history of diabetes
  • Women who have a personal history of polycystic ovarian syndrome (a tendency to develop cysts on the ovaries)

Heart Disease Risk

Metabolic syndrome increases your risk for heart disease. Heart disease risk can be divided into short-term risk and long-term risk.

"Short-term risk" refers to the risk of having a heart attack or dying from heart disease in the next 10 years. "Long-term risk" refers to the risk of developing heart disease over your lifetime.

Other risk factors, besides metabolic syndrome, also increase your risk for heart disease. For example, a high LDL cholesterol level and smoking are major risk factors for heart disease. For details about all of the risk factors for heart disease, go to the Health Topics Coronary Heart Disease Risk Factors article.

Even if you don't have metabolic syndrome, you should find out your short-term risk for heart disease. The National Cholesterol Education Program (NCEP) divides short-term heart disease risk into four categories, as shown below. Your risk category depends on which risk factors you have and how many you have.

Your risk factors are used to calculate your 10-year risk of developing heart disease. The NCEP has an online calculator that you can use to determine your 10-year heart disease risk score.

  • High risk: You're in this category if you already have heart disease or diabetes, or if your 10-year risk score is more than 20 percent.
  • Moderately high risk: You're in this category if you have two or more risk factors and your 10-year risk score is 10–20 percent.
  • Moderate risk: You're in this category if you have two or more risk factors and your 10-year risk score is less than 10 percent.
  • Lower risk: You're in this category if you have zero or one risk factor.

Even if your 10-year risk score isn't high, metabolic syndrome will increase your risk for heart disease over time. Thus, metabolic syndrome should be treated (mainly with lifestyle changes).




What Are the Signs and Symptoms of Metabolic Syndrome?

Metabolic syndrome is a group of risk factors that raises your risk for heart disease and other health problems, such as diabetes and stroke. These risk factors can increase your risk for health problems even if they're only moderately raised (borderline-high risk factors).

Most of the metabolic risk factors have no signs or symptoms, although a large waistline is a visible sign.

Some people may have symptoms of high blood sugar if diabetes—especially type 2 diabetes—is present. Symptoms of high blood sugar often include increased thirst; increased urination, especially at night; fatigue (tiredness); and blurred vision.

High blood pressure usually has no signs or symptoms. However, some people in the early stages of high blood pressure may have dull headaches, dizzy spells, or more nosebleeds than usual.




How Is Metabolic Syndrome Diagnosed?

Your doctor will diagnose metabolic syndrome based on the results of a physical exam and blood tests. You must have at least three of the five metabolic risk factors to be diagnosed with metabolic syndrome.

Metabolic Risk Factors

A Large Waistline

Having a large waistline means that you carry excess weight around your waist (abdominal obesity). This is also called having an "apple-shaped" figure. Your doctor will measure your waist to find out whether you have a large waistline.

A waist measurement of 35 inches or more for women or 40 inches or more for men is a metabolic risk factor. A large waistline means you're at increased risk for heart disease and other health problems.

A High Triglyceride Level

Triglycerides are a type of fat found in the blood. A triglyceride level of 150 mg/dL or higher (or being on medicine to treat high triglycerides) is a metabolic risk factor. (The mg/dL is milligrams per deciliter—the units used to measure triglycerides, cholesterol, and blood sugar.)

A Low HDL Cholesterol Level

HDL cholesterol sometimes is called "good" cholesterol. This is because it helps remove cholesterol from your arteries.

An HDL cholesterol level of less than 50 mg/dL for women and less than 40 mg/dL for men (or being on medicine to treat low HDL cholesterol) is a metabolic risk factor.

High Blood Pressure

A blood pressure of 130/85 mmHg or higher (or being on medicine to treat high blood pressure) is a metabolic risk factor. (The mmHg is millimeters of mercury—the units used to measure blood pressure.)

If only one of your two blood pressure numbers is high, you're still at risk for metabolic syndrome.

High Fasting Blood Sugar

A normal fasting blood sugar level is less than 100 mg/dL. A fasting blood sugar level between 100–125 mg/dL is considered prediabetes. A fasting blood sugar level of 126 mg/dL or higher is considered diabetes.

A fasting blood sugar level of 100 mg/dL or higher (or being on medicine to treat high blood sugar) is a metabolic risk factor.

About 85 percent of people who have type 2 diabetes—the most common type of diabetes—also have metabolic syndrome. These people have a much higher risk for heart disease than the 15 percent of people who have type 2 diabetes without metabolic syndrome.




How Is Metabolic Syndrome Treated?

Healthy lifestyle changes are the first line of treatment for metabolic syndrome. Lifestyle changes include losing weight, being physically active, following a heart healthy diet, and quitting smoking.

If lifestyle changes aren't enough, your doctor may prescribe medicines. Medicines are used to treat and control risk factors such as high blood pressure, high triglycerides, low HDL cholesterol, and high blood sugar.

Blood-thinning medicines, such as aspirin, also may be used to reduce the risk of blood clots. Excessive blood clotting is a condition that often occurs with metabolic syndrome.

Goals of Treatment

The major goal of treating metabolic syndrome is to reduce the risk of heart disease. Treatment is directed first at lowering LDL cholesterol and high blood pressure and managing diabetes (if these conditions are present).

The second goal of treatment is to prevent the onset of type 2 diabetes (if it hasn't already developed). Long-term complications of diabetes often include heart and kidney disease, vision loss, and foot or leg amputation.

If diabetes is present, the goal of treatment is to reduce your risk for heart disease by controlling all of your risk factors.

The main focus of treating metabolic syndrome is managing the risk factors that are within your control, such as overweight or obesity, an unhealthy diet, and an inactive lifestyle.

Lifestyle Changes

Losing Weight

If you have metabolic syndrome and are overweight or obese, your doctor will likely recommend weight loss. He or she can help you create a weight-loss plan and goals. 

The long-range target is to lower your body mass index (BMI) to less than 25. BMI measures your weight in relation to your height and gives an estimate of your total body fat.

A BMI between 25 and 29.9 is considered overweight. A BMI of 30 or more is considered obese. A BMI of less than 25 is the goal for prevention and treatment of metabolic syndrome.

You can calculate your BMI using the National Heart, Lung, and Blood Institute's (NHLBI's) online calculator, or your health care provider can calculate your BMI.

For more information about losing weight or maintaining your weight, go to the Health Topics Overweight and Obesity article.

Following a Heart Healthy Diet

A heart healthy diet is an important part of a healthy lifestyle. A healthy diet includes a variety of vegetables and fruits. These foods can be fresh, canned, frozen, or dried. A good rule is to try to fill half of your plate with vegetables and fruits.

A healthy diet also includes whole grains, fat-free or low-fat dairy products, and protein foods, such as lean meats, poultry without skin, seafood, processed soy products, nuts, seeds, beans, and peas.

Choose and prepare foods with little sodium (salt). Too much salt can raise your risk for high blood pressure. Studies show that following the Dietary Approaches to Stop Hypertension (DASH) eating plan can lower blood pressure.

Try to avoid foods and drinks that are high in added sugars. For example, drink water instead of sugary drinks, such as soda.

Also, try to limit the amount of solid fats and refined grains that you eat. Solid fats are saturated fat and trans fatty acids. Refined grains come from processing whole grains, which results in a loss of nutrients (such as dietary fiber).

If you drink alcohol, do so in moderation. Too much alcohol can raise your blood pressure and triglyceride level. Alcohol also adds extra calories, which can cause weight gain.

Aim for a healthy weight by staying within your daily calorie needs. Balance the calories you take in from food and drinks with the calories you use while doing physical activity.

For more information about following a healthy diet, go to the National Heart, Lung, and Blood Institute's "Your Guide to Lowering Your Blood Pressure With DASH" and the U.S. Department of Agriculture's ChooseMyPlate.gov Web site. Both resources provide general information about healthy eating.

Being Physically Active

Physical activity can help keep your heart and lungs healthy. Many Americans are not active enough. The good news is that even modest amounts of physical activity are good for your health. The more active you are, the more you'll benefit.

Before starting any kind of exercise program or new physical activity, talk with your doctor about the types and amounts of physical activity that are safe for you.

The four main types of physical activity are aerobic, muscle-strengthening, bone strengthening, and stretching.

You can do physical activity with light, moderate, or vigorous intensity. The level of intensity depends on how hard you have to work to do the activity. People who have metabolic syndrome usually are urged to keep up a moderate level of activity.

For more information about physical activity, go to the U.S. Department of Health and Human Services' "2008 Physical Activity Guidelines for Americans," the Health Topics Physical Activity and Your Heart article, and the NHLBI's "Your Guide to Physical Activity and Your Heart."

Smoking

If you smoke, quit. Smoking can raise your risk for heart disease and heart attack and worsen other heart disease risk factors. Talk with your doctor about programs and products that can help you quit smoking. Also, try to avoid secondhand smoke.

If you have trouble quitting smoking on your own, consider joining a support group. Many hospitals, workplaces, and community groups offer classes to help people quit smoking.

For more information about how to quit smoking, go to the Health Topics Smoking and Your Heart article and the NHLBI's "Your Guide to a Healthy Heart."

Medicines

If lifestyle changes aren't enough, your doctor may prescribe medicines to help you control your risk factors. Medicines can help treat unhealthy cholesterol levels, high blood pressure, and high blood sugar.

Unhealthy cholesterol levels are treated with medicines such as statins, fibrates, or nicotinic acid. High blood pressure is treated with medicines such as diuretics or ACE inhibitors. High blood sugar is treated with oral medicines (such as metformin), insulin injections, or both.

Low-dose aspirin can help reduce the risk of blood clots, especially for people whose risk of heart disease is high.




How Can Metabolic Syndrome Be Prevented?

Making healthy lifestyle choices is the best way to prevent metabolic syndrome. One important lifestyle choice is to maintain a healthy weight. Other than weighing yourself on a scale, you can find out if you're at a healthy weight using your waist measurement and body mass index (BMI).

A waist measurement indicates your abdominal fat, which is linked to your risk for heart disease and other diseases. To measure your waist, stand and place a tape measure around your middle, just above your hipbones. Measure your waist just after you breathe out. Make sure the tape is snug but doesn't squeeze the flesh.

A waist measurement of less than 35 inches for women and less than 40 inches for men is the goal for preventing metabolic syndrome; it's also the goal when treating metabolic syndrome.

BMI measures your weight in relation to your height and gives an estimate of your total body fat. A BMI between 25 and 29.9 is considered overweight. A BMI of 30 or more is considered obese. A BMI of less than 25 is the goal for preventing metabolic syndrome; it's also the goal when treating metabolic syndrome.

You can figure out your BMI using the National Heart, Lung, and Blood Institute's (NHLBI's) online calculator, or your doctor can help you.

To maintain a healthy weight, follow a heart healthy diet and try not to overeat. A healthy diet includes a variety of vegetables and fruits. It also includes whole grains, fat-free or low-fat dairy products, and protein foods, such as lean meats, poultry without skin, seafood, processed soy products, nuts, seeds, beans, and peas.

A healthy diet is low in sodium (salt), added sugars, solid fats, and refined grains. Solid fats are saturated fat and trans fatty acids. Refined grains come from processing whole grains, which results in a loss of nutrients (such as dietary fiber).

For more information about following a healthy diet, go to the NHLBI's "Your Guide to Lowering Your Blood Pressure With DASH" and the U.S. Department of Agriculture's ChooseMyPlate.gov Web site. Both resources provide general information about healthy eating.

Being physically active also can help you maintain a healthy weight. Before starting any kind of exercise program or new physical activity, talk with your doctor about the types and amounts of physical activity that are safe for you.

For more information about physical activity, go to the U.S. Department of Health and Human Services' "2008 Physical Activity Guidelines for Americans," the Health Topics Physical Activity and Your Heart article, and the NHLBI's "Your Guide to Physical Activity and Your Heart."

Make sure to schedule routine doctor visits to keep track of your cholesterol, blood pressure, and blood sugar levels. A blood test called a lipoprotein panel will show your levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides.




Living With Metabolic Syndrome

Metabolic syndrome is a lifelong condition. However, lifestyle changes can help you control your risk factors and reduce your risk for heart disease and diabetes.

If you already have heart disease and/or diabetes, lifestyle changes can help you prevent or delay related problems. Examples of these problems include heart attack, stroke, and diabetes-related complications (for example, damage to your eyes, nerves, kidneys, feet, and legs).

Lifestyle changes may include losing weight, following a heart healthy diet, being physically active, and quitting smoking.

If lifestyle changes aren't enough, your doctor may recommend medicines. Take all of your medicines as your doctor prescribes. For more information about lifestyle changes and medicines, go to "How Is Metabolic Syndrome Treated?"

Make realistic short- and long-term goals for yourself when you begin to make healthy lifestyle changes. Work closely with your doctor and seek regular medical care.




Clinical Trials

The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.

NHLBI-supported research has led to many advances in medical knowledge and care. For example, this research has uncovered some of the causes of various diseases and conditions, as well as ways to prevent or treat them.

The NHLBI continues to support research aimed at learning more about various diseases and conditions, including metabolic syndrome. For example, NHLBI-supported research includes studies that explore:

  • How tobacco exposure and abdominal obesity affect adolescents' risk of developing metabolic syndrome
  • The effects of two diets on the treatment of adolescents who have heart disease risk factors
  • How certain medicines can help treat metabolic syndrome
  • The effects of sugar-sweetened beverages on cholesterol, triglyceride, and blood sugar levels

Much of this research depends on the willingness of volunteers to take part in clinical trials. Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions.

For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.

By taking part in a clinical trial, you can gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.

If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.

If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.

For more information about clinical trials related to metabolic syndrome, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:

For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.




Links to Other Information About Metabolic Syndrome

NHLBI Resources

Non-NHLBI Resources

Clinical Trials

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November 03, 2011 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.

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