Metabolic syndrome is diagnosed when at least three of five features are present: a waist over 40 inches (men) or 35 inches (women); triglycerides at or above 150 mg/dL; HDL cholesterol below 40 mg/dL (men) or 50 mg/dL (women); blood pressure at or above 130/85 mmHg; and fasting glucose at or above 100 mg/dL. The common thread is insulin resistance driven by abdominal fat. It roughly doubles the risk of cardiovascular disease and raises the risk of type 2 diabetes about fivefold, and it responds to the same changes that improve insulin resistance.
What is metabolic syndrome?
Metabolic syndrome is the name for a cluster of measurements that, together, mark a person as being at high risk of cardiovascular disease and type 2 diabetes. It is defined by counting: three or more of five criteria.
| Criterion | Threshold |
|---|---|
| Waist circumference | 40 inches (102 cm) or more in men; 35 inches (88 cm) or more in women (lower cut-offs for Asian populations) |
| Triglycerides | 150 mg/dL (1.7 mmol/L) or higher, or on treatment |
| HDL cholesterol | Below 40 mg/dL (1.0 mmol/L) in men; below 50 mg/dL (1.3 mmol/L) in women, or on treatment |
| Blood pressure | 130/85 mmHg or higher, or on treatment |
| Fasting glucose | 100 mg/dL (5.6 mmol/L) or higher, or on treatment |
About one in three American adults meets the definition, and prevalence rises steeply with age. Raised fasting glucose is often the last criterion to appear.
The value of the label is not that it explains anything new — each criterion is a risk factor in its own right — but that it draws attention to the pattern. Someone with a large waist, borderline triglycerides and borderline blood pressure may have three "mild" results that individually attract no action, and yet carry substantially elevated risk together.
Why the five features cluster
The link is insulin resistance, driven mostly by fat stored around the abdominal organs.
Visceral fat releases fatty acids and inflammatory signals into the blood supply of the liver. The liver responds by producing more triglyceride-rich particles and by becoming insulin resistant itself, which raises fasting glucose. High triglycerides in turn drive down HDL cholesterol through an exchange process between particles. High insulin levels promote sodium retention by the kidneys and stiffen blood vessels, raising blood pressure. Each feature feeds the others, and all of them trace back to the same source.
This is why the waist measurement is often the first criterion to be met and the most useful to watch.
Who is at risk
The risk factors are those of insulin resistance: excess weight (particularly abdominal), physical inactivity, age, a family history of diabetes or early heart disease, poor sleep or sleep apnea, and certain conditions including polycystic ovary syndrome and fatty liver disease. Some ancestries carry higher risk at lower body weight.
Symptoms
Metabolic syndrome has no symptoms of its own. A large waist is visible, and the signs of insulin resistance — darkened skin folds, skin tags, energy dips — may be present, but blood pressure, triglycerides, HDL and glucose in the ranges above are silent. It is found by measuring.
How it is diagnosed
A waist measurement, a blood pressure reading, and a fasting blood sample for lipids and glucose. All are routine, and all are usually done in an annual check or a cardiovascular risk assessment.
Why it matters
Metabolic syndrome roughly doubles the risk of heart attack and stroke over the following decade and raises the risk of developing type 2 diabetes about fivefold. It is also associated with fatty liver disease, sleep apnea, kidney disease, gout, and polycystic ovary syndrome.
Cardiovascular risk is what drives treatment decisions. Doctors increasingly use a formal risk calculator (such as the pooled cohort equations in the United States or QRISK in the United Kingdom) that incorporates the individual measurements, age, sex, smoking and other factors, rather than the syndrome label alone.
Management
Because the features share a cause, they respond to the same measures — and improvements in one tend to bring improvements in the others.
Weight and waist
Losing 5–10% of body weight typically lowers triglycerides, blood pressure and glucose and raises HDL. The loss of visceral fat, which happens early in weight loss, is what matters most.
Physical activity
At least 150 minutes a week of moderate aerobic activity plus resistance training two or three times a week. Exercise improves each criterion independently of weight loss, particularly triglycerides, HDL and glucose.
Eating pattern
Mediterranean-style patterns have the most direct trial evidence for metabolic syndrome, reducing the number of criteria met and cardiovascular events. Common features of effective patterns: more vegetables, legumes, whole grains, nuts and fish; less refined carbohydrate, sugar-sweetened drinks and processed meat; alcohol in moderation or not at all (alcohol raises triglycerides and blood pressure).
Sleep
Untreated sleep apnea worsens every criterion. Snoring, witnessed pauses in breathing, or unrefreshing sleep are reasons to be assessed.
Smoking
Stopping smoking is the single largest reduction in cardiovascular risk available to a smoker with metabolic syndrome.
Medication
Each feature is treated on its own evidence. Blood pressure persistently above 130/80 mmHg is usually treated with medication. Statins are recommended for many people with metabolic syndrome based on calculated cardiovascular risk, regardless of the LDL cholesterol value. Metformin may be considered for raised glucose (see the prediabetes guide) in people at high risk of diabetes. There is no medication for "metabolic syndrome" as a whole.
When to contact a doctor
If you have a large waist and have not had blood pressure, lipids and glucose measured in the past year, ask for them. If you meet the criteria, ask for a formal cardiovascular risk assessment and for guidance on which features warrant treatment. Chest pain, breathlessness on exertion, or symptoms of high blood sugar need prompt attention regardless.
Frequently asked questions
Is metabolic syndrome the same as prediabetes?
They overlap but are not the same. Prediabetes is defined by glucose alone. Metabolic syndrome requires three of five features, and raised glucose is only one of them; a person can have metabolic syndrome with normal glucose, or prediabetes without the other features.
Can metabolic syndrome be reversed?
The individual features can return to normal — often with 5–10% weight loss and regular activity — at which point the criteria are no longer met. Whether the underlying tendency is gone depends on maintaining those changes.
Do I need medication?
Each feature is treated on its own merits. High blood pressure and high LDL cholesterol usually warrant medication if lifestyle change is not enough; raised triglycerides and glucose often improve substantially with lifestyle change alone.
References
- NIDDK. Insulin Resistance & Prediabetes (2023). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Type 2 Diabetes (2023). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/type-2-diabetes
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