PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
The metabolic syndrome refers to a clustering of cardiovascular disease (CVD) risk factors whose underlying pathophysiology may be related to insulin resistance. Metabolic syndrome is also associated with an increased risk of some common cancers.
However, there is uncertainty as to whether all patients with the syndrome are indeed insulin-resistant, so the aetiology has been broadened to include concepts of obesity, adipose tissue disorders and other factors.
Metabolic syndrome is common in adults and can also occur in obese children. Metabolic syndrome can also occur in lean individuals, suggesting that obesity is a marker for the syndrome, not a cause.
Any three (or more) of the following factors constitute a diagnosis of metabolic syndrome:
- Increased waist circumference: ethnicity specific - eg, Caucasian men ≥94 cm and women ≥80 cm; South Asian men ≥90 cm and women ≥80 cm.
- If body mass index is over 30 kg/m2, central obesity can be assumed and waist circumference does not need to be measured.
- Raised triglycerides:
- >150 mg/dL (1·7 mmol/L)
- Or specific treatment for this lipid abnormality
- Reduced HDL-cholesterol:
- <40 mg/dL (1·03 mmol/L) in men
- <50 mg/dL (1·29 mmol/L) in women
- Or specific treatment for this lipid abnormality
- Raised blood pressure:
- Systolic ≥130 mm Hg
- Diastolic ≥85 mm Hg
- Or treatment of previously diagnosed hypertension
- Raised fasting plasma glucose:
- Fasting plasma glucose ≥100 mg/dL (5·6 mmol/L)
- Most people with type 2 diabetes will have metabolic syndrome based on these criteria
The IDF proposed a definition for children and adolescents in 2007:
- Aged 6-9: waist circumference 90th percentile; however, metabolic syndrome cannot be diagnosed, but further measurements should be made if there is a family history of metabolic syndrome, type 2 diabetes, dyslipidaemia, CVD, hypertension and/or obesity.
- Aged 10-15: waist circumference ≥90th percentile or adult cut-off if lower:
- Triglycerides ≥1.7 mmol/L (≥150 mg/dL), HDL-C <1.03 mmol/L (<40 mg/dL)
- Systolic blood pressure ≥130 or diastolic blood pressure ≥85 mm Hg
- Fasting blood glucose ≥5.6 mmol/L (100 mg/dL)
- Aged 16+: use existing IDF criteria for adults.
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More recently, the usefulness of the 'metabolic syndrome' concept has been questioned - at least in so far as clinical practice is concerned:
- It is accepted that cardiovascular risk factors often 'cluster', and that insulin resistance has an important part in this risk factor clustering.
- However, recent evidence suggests that, in clinical practice, the diagnosis of metabolic syndrome is no better at predicting cardiovascular risk than the standard methods of cardiovascular risk calculation - indeed, metabolic syndrome may perform worse in cardiovascular prediction than the standard methods.
- Also, in terms of predicting diabetes, a fasting plasma glucose is a better predictor than the diagnosis of metabolic syndrome.
However, it has been pointed out that, although the metabolic syndrome appears to have limited utility for the identification of individuals at increased risk of type 2 diabetes or CVD, the diagnosis of metabolic syndrome presents an opportunity to deliver co-ordinated care to those with metabolic syndrome.
Some studies have found significant association with metabolic syndrome - eg, can identify people with diabetes without prior CVD who have a lower risk of future cardiovascular events.
- Metabolic syndrome is a growing epidemic throughout the world. Approximately 1 adult in every 4 or 5, depending on the country, has metabolic syndrome.
- The incidence increases with age; it has been estimated that in people over 50 years of age, metabolic syndrome affects more than 40% of the population in the United States of America and nearly 30% in Europe.
- The worldwide prevalence of obesity has doubled in the last two decades. The prevalence of obesity and metabolic syndrome varies between different countries and ethnic groups.
- Insulin resistance.
- Lack of physical activity.
- Atherogenic diet and atherogenic dyslipidaemia.
- Prothrombotic and pro-inflammatory states.
- Other possible factors - eg, catecholamines, antiretroviral therapy. Many others are discussed in the literature.
- Management of the underlying risk factors for CVD and diabetes (see box, below).
- Treatment of any established disease such as hypertension, heart disease, diabetes or chronic kidney disease.
- Evaluation and treatment of all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the metabolic syndrome.
CVD risk factors to evaluate and treat
- Lifestyle - smoking, physical inactivity, unhealthy diet.
- Adverse lipid profile.
Unalterable risk factors are age, sex, race, family history.
Lifestyle advice for the metabolic syndrome
Lifestyle modifications are effective in resolving metabolic syndrome and reducing the severity of related abnormalities (fasting blood glucose, waist circumference, systolic and diastolic blood pressure, and triglycerides) in people with metabolic syndrome.
30-60 minutes daily of moderate-intensity aerobic activity plus an increase in daily lifestyle activities (depending on individual fitness and co-existing disease). Many studies have shown the benefits of exercise.
Weight reduction is important for those with abdominal obesity and the metabolic syndrome. The initial aim is a slow reduction of 7-10% in baseline weight, with normal body mass index as the ultimate goal.
- Fresh fruit and vegetables (at least five portions/day).
- Complex rather than simple carbohydrates (starch not sugar); wholegrain or high-fibre rather than refined carbohydrate.
- There is evidence showing that subjects adherent to a Mediterranean diet have lower prevalence and incidence rates of metabolic syndrome than those non-adherent.
- Reduction of dietary fat is traditional advice. However, 'low fat' is too simplistic and may even be detrimental. The composition of dietary fats is more important.
- Avoid 'trans fats' (often labelled as 'hydrogenated' or 'partially hydrogenated' vegetable oils) as they are harmful and linked to cardiovascular disease.
- Increase the proportion of mono-unsaturated fats (eg, olive oil).
- Increase the amount of omega-3 polyunsaturated fatty acids (PUFAs) compared with a Western diet.
- Carbohydrates: the established view is that complex carbohydrates should form the major proportion of calories in the diet.
Other lifestyle factors
- The manifestations and complications of metabolic syndrome should be treated according to established guidelines for the treatment of hyperlipidaemia, CVD, hypertension and diabetes. This may therefore involve the use of:
- Low-dose aspirin
- Statins and/or fibrates
- Antidiabetic drugs
- There is no specific drug treatment for the metabolic syndrome itself. Metformin, glitazones and acarbose have been suggested as either improving the syndrome or delaying progression to type 2 diabetes. However, recent safety concerns do not favour glitazones.
- The AHA currently does not recommend drugs solely for the purpose of preventing diabetes, because their cost-effectiveness and safety in this role has not been documented.
- Metformin may have a role in polycystic ovary syndrome.
- Regular follow-up to monitor progress in reducing cardiovascular risk.
- Arguably, a glucose tolerance test should be performed for people with the metabolic syndrome who have normal fasting glucose, as this may identify some with occult diabetes.
Further reading & references
- Esposito K, Chiodini P, Colao A, et al; Metabolic syndrome and risk of cancer: a systematic review and meta-analysis. Diabetes Care. 2012 Nov;35(11):2402-11. doi: 10.2337/dc12-0336.
- Kahn R, Buse J, Ferrannini E, et al; The metabolic syndrome: time for a critical appraisal: joint statement from the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care. 2005 Sep;28(9):2289-304.
- Weiss R, Bremer AA, Lustig RH; What is metabolic syndrome, and why are children getting it? Ann N Y Acad Sci. 2013 Apr;1281:123-40. doi: 10.1111/nyas.12030. Epub 2013 Jan 28.
- Reaven GM; The metabolic syndrome: is this diagnosis necessary?; Am J Clin Nutr. 2006 Jun;83(6):1237-47
- Grundy SM, Cleeman JI, Daniels SR, et al; Diagnosis and management of the metabolic syndrome: an American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement. Circulation. 2005 Oct 25;112(17):2735-52. Epub 2005 Sep 12.
- Alberti KG, Eckel RH, Grundy SM, et al; Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity. Circulation. 2009 Oct 20;120(16):1640-5. doi: 10.1161/CIRCULATIONAHA.109.192644. Epub 2009 Oct 5.
- Zimmet P, Alberti G, Kaufman F, et al; The metabolic syndrome in children and adolescents. Lancet. 2007 Jun 23;369(9579):2059-61.
- Kahn R; Metabolic syndrome--what is the clinical usefulness? Lancet. 2008 Jun 7;371(9628):1892-3. Epub 2008 May 22.
- Sattar N, McConnachie A, Shaper AG, et al; Can metabolic syndrome usefully predict cardiovascular disease and diabetes? Lancet. 2008 Jun 7;371(9628):1927-35. Epub 2008 May 22.
- Taslim S, Tai ES; The relevance of the metabolic syndrome. Ann Acad Med Singapore. 2009 Jan;38(1):29-5.
- Scott R, Donoghoe M, Watts GF, et al; Impact of metabolic syndrome and its components on cardiovascular disease event rates in 4900 patients with type 2 diabetes assigned to placebo in the FIELD randomised trial. Cardiovasc Diabetol. 2011 Nov 21;10:102. doi: 10.1186/1475-2840-10-102.
- Canale MP, Manca di Villahermosa S, Martino G, et al; Obesity-related metabolic syndrome: mechanisms of sympathetic overactivity. Int J Endocrinol. 2013;2013:865965. doi: 10.1155/2013/865965. Epub 2013 Oct 31.
- Misra A, Shrivastava U; Obesity and dyslipidemia in South Asians. Nutrients. 2013 Jul 16;5(7):2708-33. doi: 10.3390/nu5072708.
- Dandona P, Aljada A, Chaudhuri A, et al; Metabolic syndrome: a comprehensive perspective based on interactions between obesity, diabetes, and inflammation. Circulation. 2005 Mar 22;111(11):1448-54.
- Kolovou GD, Anagnostopoulou KK, Cokkinos DV; Pathophysiology of dyslipidaemia in the metabolic syndrome. Postgrad Med J. 2005 Jun;81(956):358-66.
- Barbaro G, Barbarini G; Highly active antiretroviral therapy-associated metabolic syndrome and cardiovascular risk. Chemotherapy. 2006;52(4):161-5. Epub 2006 May 2.
- Lipid modification - cardiovascular risk assessment and the modification of blood lipids for the primary and secondary prevention of cardiovascular disease; NICE Clinical Guideline (May 2008, amended May 2010)
- Yamaoka K, Tango T; Effects of lifestyle modification on metabolic syndrome: a systematic review and meta-analysis. BMC Med. 2012 Nov 14;10:138. doi: 10.1186/1741-7015-10-138.
- Grosso G, Mistretta A, Marventano S, et al; Beneficial Effects of the Mediterranean Diet on Metabolic Syndrome. Curr Pharm Des. 2013 Dec 5.
- Feldeisen SE, Tucker KL; Nutritional strategies in the prevention and treatment of metabolic syndrome. Appl Physiol Nutr Metab. 2007 Feb;32(1):46-60.
- Mozaffarian D, Aro A, Willett WC; Health effects of trans-fatty acids: experimental and observational evidence. Eur J Clin Nutr. 2009 May;63 Suppl 2:S5-21.
- No authors listed; JBS 2: Joint British Societies' guidelines on prevention of cardiovascular disease in clinical practice. Heart. 2005 Dec;91 Suppl 5:v1-52
- Petersen JL, McGuire DK; Impaired glucose tolerance and impaired fasting glucose--a review of diagnosis, clinical implications and management. Diab Vasc Dis Res. 2005 Feb;2(1):9-15.
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Dr Naomi Hartree
Dr Colin Tidy
Dr Adrian Bonsall