Metabolic syndrome is the name for a group of risk factors linked to overweight and obesity that increase your chance 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 behaviors or conditions that increase your chance of getting a disease. In this article, "heart disease" refers to coronary artery disease.
The five conditions listed below are metabolic risk factors for heart disease. A person can develop any one of these risk factors by itself, but they tend to occur together. Metabolic syndrome is diagnosed when a person has at least three of these heart disease risk factors:
The more of these risk factors you have, the greater your chance of developing heart disease, diabetes, or a stroke. In general, a person with metabolic syndrome is twice as likely to develop heart disease and five times as likely to develop diabetes as someone without metabolic syndrome.
Other risk factors aside from those of the metabolic syndrome also increase your risk for heart disease. A high level of LDL cholesterol (low-density lipoprotein cholesterol; considered "bad" cholesterol) and smoking, for example, are key risk factors for heart disease, but they aren't components of metabolic syndrome. Even a single risk factor raises your risk for heart disease, and every risk factor should be lowered to reduce the risk.
The chance of developing metabolic syndrome is closely linked to being overweight or obese and to a lack of physical activity. Another cause is insulin resistance. Insulin resistance is a condition in which the body can't use its insulin properly. Insulin is a hormone the body uses to help change blood sugar into energy. Insulin resistance can lead to high blood sugar levels and is closely linked with being overweight or obese.
Genetics (ethnicity and family history) and older age are other important underlying causes of metabolic syndrome.
About 47 million adults in the United States (almost 25 percent) have metabolic syndrome, and the numbers continue to grow. The increasing number of people with this condition is connected to the rise in obesity rates among adults. In the future, metabolic syndrome may overtake smoking as the leading risk factor for heart disease.
It's possible to prevent or delay metabolic syndrome, mainly with lifestyle changes. A healthy lifestyle is a lifelong commitment. Successfully controlling metabolic syndrome takes a long-term effort and teamwork with your health care providers.
What causes metabolic syndrome?
Metabolic syndrome has several causes that act together. Some can be controlled, while others can't.
Causes that can be controlled include overweight and obesity, lack of physical activity, and insulin resistance.
Some causes you can't control are growing older and genetics. Your chance of developing metabolic syndrome increases with age. Your genes can increase your chances of developing insulin resistance, for example, which can lead to metabolic syndrome, even if you have only a little extra weight around your waist.
Two other conditions are often found in people with metabolic syndrome, although it's not known if they cause it or worsen it. The two conditions are a tendency to form blood clots and a tendency to have a constant, low-grade inflammation throughout the body.
Additional conditions that are being studied to see whether they have links to metabolic syndrome include:
Who is at risk for metabolic syndrome?
You're at greatest risk for metabolic syndrome if you have these underlying causes:
Some people are at risk for metabolic syndrome because the medicines they take may cause weight gain or changes in blood pressure, cholesterol, and blood sugar levels. These medicines are most often used for inflammation, allergies, HIV, and depression and other kinds of mental illnesses.
About 47 million adults in the United States (almost 25 percent) have metabolic syndrome. Metabolic syndrome is more common in African American women than in African American men and in Mexican American women than in Mexican American men. It affects White women and men roughly equally.
Some racial and ethnic groups in the United States are more at risk for metabolic syndrome than others. Mexican Americans have the highest rate of metabolic syndrome (31.9 percent). Caucasians (23.8 percent) and African Americans (21.6 percent) have lower rates.
Other groups that are at increased risk of developing metabolic syndrome include:
In addition, members of certain ethnic groups are at increased risk for metabolic syndrome. For example, South Asians have an increased risk for metabolic syndrome.
Risk for heart disease
Having metabolic syndrome increases your risk for heart disease. Heart disease risk can be divided into short-term risk (the risk for having a heart attack or dying of heart disease in the next 10 years) and long-term risk (the risk for developing heart disease over your lifetime).
Other factors (aside from metabolic syndrome) contribute to your risk for heart disease as well. The major risk factors are:
If you smoke cigarettes or have increased LDL cholesterol or high blood pressure, these are the first targets of treatment.
Regardless of whether you have metabolic syndrome, you should find out your chance of developing heart disease in the next 10 years (your short-term risk). This will help decide what your LDL cholesterol goal should be and how you should be treated. To start, you will need to count how many risk factors you have from the list above. (Don't count LDL and total cholesterol because the treatment for them will be geared to your level of risk.)
The National Cholesterol Education Program (NCEP) divides short-term heart disease risk into four categories, as shown below. Your risk category depends on the number of risk factors you have and which ones they are.
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. Every person with metabolic syndrome should have their 10-year-risk score calculated.
Even if your 10-year-risk score isn't high, over time metabolic syndrome will increase your chance for heart disease. This means that, regardless of your short-term risk category, metabolic syndrome should be treated (mainly with lifestyle changes).
What are the signs and symptoms of metabolic syndrome?
Metabolic syndrome is made up of a group of factors that can increase risk even if they are only moderately raised (borderline-high risk factors). Metabolic syndrome itself usually has no symptoms. Most of the risk factors linked to metabolic syndrome have no signs or symptoms, although a large waistline is a visible sign.
Some people may have symptoms of high blood sugar (if diabetes is present) or, occasionally, high blood pressure. Symptoms of high blood sugar often include increased thirst; increased urination, especially at night; fatigue (tiredness); and blurred vision. High blood pressure is generally considered to have no signs or symptoms. However, a few 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?
The diagnosis of metabolic syndrome is based on the results of a physical exam and blood tests. To be diagnosed with metabolic syndrome, you must have at least three out of five of the following risk factors:
About 85 percent of people who have type 2 diabetes (the most common type) 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, but don't have metabolic syndrome.
How is metabolic syndrome treated?
Healthy lifestyle changes are the first line of treatment for metabolic syndrome. Lifestyle changes include weight loss, increased physical activity, an improved diet, and quitting smoking.
Medicines are the next line of treatment. They're used to treat and control individual risk factors such as high blood pressure, high triglycerides, low HDL cholesterol (high-density lipoprotein cholesterol), and high blood sugar. Medicines such as aspirin also may be used to reduce the risk of blood clots, a condition that often occurs with metabolic syndrome.
Goals of treatment
The major goal of treating metabolic syndrome is to reduce a person's risk for heart disease. Treatment is directed first at reducing LDL cholesterol (low-density lipoprotein cholesterol), high blood pressure, and 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 the increased risk for heart disease by controlling all of the risk factors.
The main emphasis in the treatment of metabolic syndrome is to lessen the effects of the underlying risk factors that can be controlled, such as overweight, lack of physical activity, and an unhealthy diet.
Specific types of treatment
In general, people with metabolic syndrome who are overweight or obese are urged to reduce their weight by 7 to 10 percent during the first year of treatment. For example, a person weighing 250 pounds should try to lose 18 to 25 pounds. A person weighing 300 pounds should try to lose 21 to 30 pounds.
After the first year, people are urged to continue to lose weight to the extent possible, with a long-range target of lowering their 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.
Healthy eating plan
For a healthy eating plan, go to the NHLBI's Aim for a Healthy Weight Web site and the NHLBI's "Your Guide to Lowering Cholesterol With TLC." This booklet describes the Therapeutic Lifestyle Changes (TLC) diet.
With the TLC diet, less than 7 percent of your daily calories should come from saturated fat, and no more than 25 to 35 percent of your daily calories should come from all fats, including saturated, trans, monounsaturated, and polyunsaturated fats. You also should consume less than 200 mg a day of cholesterol. The amounts of fat and cholesterol in prepared foods can be found on the food's nutritional label.
Foods high in soluble fiber also are part of a healthy eating plan. These foods include:
Fish are an important part of a heart healthy diet. Fish are a good source of omega-3 fatty acids, which may help protect the heart from blood clots and inflammation and reduce the risk for heart attack.
You also should try to limit the amount of sodium and salt that you eat. This means choosing low-sodium and low-salt foods and "no added salt" foods and seasonings at the table or when cooking. The nutritional label on food packaging shows the amount of sodium in the item.
Try to limit alcoholic beverages. Too much alcohol will raise your blood pressure and triglyceride level. It will also add extra calories, which will cause weight gain. Men should have no more than two drinks containing alcohol a day. Women should have no more than one drink containing alcohol a day.
Increased physical activity
In general, people with metabolic syndrome are urged to keep up a moderate level of activity, such as brisk walking for at least 30 minutes at least 5 days of the week. This activity can be broken into shorter periods as needed – for example, three 10-minutes sessions.
The ultimate goal is for people to maintain a moderate level of physical activity 60 minutes a day for 5 days a week, but preferably daily. You should talk with your doctor about the best kind of physical activity for you before starting any kind of program.
If you smoke, quitting is important. Among other known harmful effects on your heart, smoking will raise your triglyceride level and lower your HDL cholesterol.
Your doctor may recommend medicines to help treat unhealthy cholesterol levels, high blood pressure, and high blood sugar. Unhealthy cholesterol levels are treated by one or more cholesterol-lowering medicines such as statins, fibrates, or nicotinic acid.
High blood pressure is treated by one or more antihypertensive medicines such as diuretics or angiotensin-converting enzyme (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 forming blood clots, especially for people at high risk for heart disease.
How can metabolic syndrome be prevented?
Making healthy lifestyle choices is the best way to prevent metabolic syndrome. Maintaining a healthy weight is important. Other than weighing yourself on a scale, there are two ways to know whether you're at a healthy weight: waist measurement and body mass index (BMI).
A waist measurement indicates your abdominal fat and 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 provides 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, and it's also the goal when treating metabolic syndrome.
To maintain a healthy weight, follow a healthy eating plan and try not to overeat. This means eating fewer calories and less saturated fat, and emphasizing whole grains, fish, and fruits and vegetables. Choose unsaturated fats when eating fats and oils such as canola, olive, or safflower oils, soft or liquid margarine, and nuts.
Increasing your physical activity also can help you maintain a healthy weight. Talk to your doctor about what kind of physical activity is best for you. If you're medically able, get at least 30 minutes of moderate activity, such as brisk walking, at least 5 days a week. With your doctor's permission, work up to getting 60 minutes of moderate activity 5 to 7 days a week.
Make sure to schedule regular doctor visits to keep track of your cholesterol, blood pressure, and blood sugar levels. A cholesterol blood test will show your levels of LDL cholesterol (low-density lipoprotein cholesterol), HDL cholesterol (high-density lipoprotein), and triglycerides.