Metabolic syndrome is characterized by a large waist circumference (due to excess abdominal adipose tissue), hypertension, abnormal fasting plasma glucose or insulin resistance, and dyslipidemia. Causes, complications, diagnosis, and treatment are similar to those of obesity.
The incidence of metabolic syndrome often parallels that of obesity and type 2 diabetes. The prevalence of metabolic syndrome increases with age, and in one United States study, it was approximately 23% in the general population and was 44% for people aged 60 to 69 years and 42% in those aged ≥ 70 years (1). Children and adolescents can develop metabolic syndrome, but in these age groups, no strict definition is established.
Development of metabolic syndrome depends on distribution as well as amount of adipose tissue. Excess central adiposity (called apple shape), particularly when it results in a high waist-to-hip ratio (reflecting a relatively low muscle-to-fat mass ratio), increases risk. The syndrome is less common among people who have excess subcutaneous fat around the hips (called pear shape) and a low waist-to-hip ratio (reflecting a higher muscle-to-fat mass ratio).
Excess abdominal fat leads to excess free fatty acids in the portal vein, increasing fat accumulation in the liver. Fat also accumulates in muscle cells. Insulin resistance develops, with hyperinsulinemia. Glucose metabolism is impaired, and dyslipidemias and hypertension develop. Serum uric acid levels are typically elevated (increasing risk of gout), and a prothrombotic state (with increased levels of fibrinogen and plasminogen activator inhibitor I) and an inflammatory state develop.
Some experts think that chronic stress causes hormonal changes that contribute to abdominal obesity, insulin resistance, and low blood lipid (HDL) levels.
Risks of metabolic syndrome include
Polycystic ovary syndrome (for women)
Low plasma testosterone, erectile dysfunction, or both (for men)
Smoking (which can increase triglyceride levels and decrease HDL levels)
Reference
1. Ford ES, Giles WH, Dietz WH: Prevalence of the metabolic syndrome among US adults: Findings from the third National Health and Nutrition Examination Survey. JAMA 287 (3):356–359, 2002. doi: 10.1001/jama.287.3.356
Diagnosis of Metabolic Syndrome
Waist circumference and blood pressure
Fasting plasma glucose and a lipid profile
Screening for metabolic syndrome is important. A family history plus measurement of waist circumference and blood pressure are part of routine care. If patients with a family history of type 2 diabetes mellitus, particularly those ≥ 40 years, have a waist circumference greater than that recommended for their race and sex, fasting plasma glucose and a lipid profile must be determined.
Metabolic syndrome has many different definitions, but it is most often diagnosed when ≥ 3 of the following are present (see table Criteria Often Used for Diagnosis of Metabolic Syndrome):
Excess abdominal fat
A high fasting plasma glucose level
A high triglyceride level
A low high-density lipoprotein (HDL) cholesterol level
Criteria Often Used for Diagnosis of Metabolic Syndrome*
Criteria | Value |
|---|---|
Waist circumference (cm [in]) | ≥ 102 (≥ 40) for men ≥ 88 (≥ 35) for women |
Fasting glucose (mg/dL [mmol/L]) | ≥ 100 (≥ 5.6) |
Blood pressure (mm Hg) | ≥ 130/85 |
Triglycerides, fasting (mg/dL [mmol/L]) | ≥ 150 (≥ 1.7) |
High-density lipoprotein (HDL) cholesterol (mg/dL [mmol/L]) | < 40 (< 1.04) for men < 50 (< 1.29) for women |
* At least 3 of the criteria must be present for the diagnosis. | |
Treatment of Metabolic Syndrome
Heart-healthy diet and physical activity
Medications such as metformin and statins
Anti-obesity medications and metabolic and bariatric surgery
Smoking cessation
Stress management
Optimally, a management approach based on a heart-healthy diet and regular physical activity results in weight loss; physical activity includes a combination of aerobic activity and resistance training, reinforced with behavioral therapy. Metformin, an insulin sensitizer, or a thiazolidinedione (eg, rosiglitazone, pioglitazone) may be useful. Weight loss of ≈ 7% may be sufficient to reverse the syndrome, but if not, each feature of the syndrome should be managed to achieve recommended targets; available medications are very effective.
Obesity is treated with anti-obesity medications (eg, orlistat, phentermine, liraglutide) and, if needed, metabolic and bariatric surgery
Other cardiovascular risk factors (eg, smoking cessation) also need to be managed. Increased physical activity has cardiovascular benefits even if weight is not lost.
Patients with dyslipidemia may be treated with statins.
Stress management (eg, deep breathing exercises, meditation, psychologic support, counseling) is recommended.
Key Points
Excess abdominal adiposity leads to abnormal fasting plasma glucose or insulin resistance, dyslipidemias, and hypertension; having 3 or more of these conditions defines metabolic syndrome.
Metabolic syndrome is extremely common (eg, prevalence in the United States of possibly > 40% in people > 60 years).
Determine waist circumference, blood pressure, fasting plasma glucose, and lipid profile.
Emphasize following a healthy diet and exercising, and manage cardiovascular risk factors; if these measures are not completely effective, consider use of anti-obesity medications and/or metabolic and bariatric surgery.
