Metabolic Syndrome

What metabolic syndrome is

Metabolic syndrome is a name for a cluster: central obesity, a raised triglyceride, a low HDL cholesterol, a raised blood pressure and a raised fasting glucose, occurring together in one person more often than chance would predict. The 2009 harmonising statement describes it exactly that way — "A cluster of risk factors for cardiovascular disease and type 2 diabetes mellitus, which occur together more often than by chance alone, have become known as the metabolic syndrome." Note what that sentence is and is not. It is an observation about co-occurrence. It is not a mechanism, and it does not name a disease process.

The proposed mechanism behind the clustering is insulin resistance, and the interesting thing is that no definition requires it to be measured. ATP III declined to include it, stating that the panel "did not find adequate evidence to recommend routine measurement of insulin resistance (e.g., plasma insulin), proinflammatory state (e.g., high-sensitivity C-reactive protein), or prothrombotic state (e.g., fibrinogen or PAI-1) in the diagnosis of the metabolic syndrome". The IDF reached the same place by a different route: insulin resistance "is not an essential requirement" because it is difficult to measure in day-to-day clinical practice. So the syndrome named for insulin resistance is diagnosed without measuring it — which is also why our HOMA-IR calculator refuses to print a single cut-off.

The definitions differ most on central obesity, and not by accident. The IDF made it obligatory and wrote the requirement into the definition itself: "According to the new IDF definition, for a person to be defined as having the metabolic syndrome they must have: Central obesity (defined as waist circumference* with ethnicity specific values) plus any two of the following four factors". ATP III made it one component of five. The 2009 meeting was convened to settle this and settled half of it — the obligatory requirement was dropped, and the threshold was not agreed.

Why any of it matters is the part worth holding on to. The cluster predicts cardiovascular disease and type 2 diabetes, and the IDF notes that people with type 2 diabetes who also have the syndrome "carry a much higher risk of CVD than those who have type 2 diabetes alone". What is disputed is whether naming the cluster adds anything to measuring and treating its parts. On that, the two diabetes bodies say no and the IDF says yes, and both are quoted below.

There are no symptoms, and that is the point

Metabolic syndrome produces nothing you can feel. Not one of the five components has a symptom attached to it at the thresholds used here. A fasting glucose of 105 mg/dL feels like nothing. A triglyceride of 180 mg/dL feels like nothing. A blood pressure of 134/86 feels like nothing, and an HDL of 36 mg/dL feels like nothing. This is the whole reason the condition is defined by measurements rather than by a presentation.

That has one useful consequence and one dangerous one. The useful one is that there is no symptom list on this page to argue about, and no way for a man to talk himself out of the numbers by not feeling unwell. The dangerous one is the mirror image: feeling fine is not evidence of anything, and the men most likely to dismiss a borderline set of results are the ones who feel well.

The one component people believe they can assess is the waist, and the IDF does say it can be self-measured — "The initial step is to measure waist circumference. This can be done by people themselves." But the IDF also specifies the tape position, and the threshold you measure against depends on ancestry rather than country of residence. A number taken at the navel rather than at the specified landmark, compared against a threshold chosen from the wrong table, is two errors deep before anyone has interpreted it.

The two structured findings below are the laboratory ones, and they are structured because they are the components a man genuinely cannot assess about himself. The waist is deliberately not structured here, despite being a component: it is discussed in prose instead, because a page that emitted all five components as machine-readable signs would have published the tick-list it just spent three paragraphs explaining it cannot honestly publish.

The signs that are specific — and none of them are self-assessable

A fasting plasma glucose, and what follows it

One of the five components and a laboratory measurement, not something a man can estimate. The IDF sets the line at 100 mg/dL (5.6 mmol/L) and adds a step most summaries drop: "If above 5.6 mmol/L or 100 mg/dL, OGTT is strongly recommended but is not necessary to define presence of the syndrome." The tolerance test is a two-hour clinical procedure and it is looking for something the single number can miss.

Fasting triglycerides and HDL cholesterol on a standardised lipid panel

Two of the five components, from one fasting sample. The criterion is met by treatment as well as by the number — the IDF wording for both lipid components is "or specific treatment for this lipid abnormality" — so a man whose lipids are now controlled on a statin or a fibrate still meets the component, which is a fact about his history rather than about today’s result.

The diagnostic criteria, quoted

Each criterion below is the guideline’s own wording, not a summary of it. Our reading follows underneath, so you can weigh one against the other.

1. The American working definition: three of five

   “the metabolic syndrome is identified by the presence of three or more of the components listed in Table II.6-1”

   The five components and the lines ATP III drew for a man: waist circumference over 102 cm (over 40 in), triglycerides at or above 150 mg/dL, HDL cholesterol below 40 mg/dL, blood pressure at or above 130/85 mmHg, and fasting glucose at or above 110 mg/dL. No component is obligatory and any three will do, so the same label covers a man who is thin with three abnormal bloods and a man with a large waist, a low HDL and a raised blood pressure. Those are not the same patient.

2. And the sentence ATP III put immediately before its own table

   “There are no well-accepted criteria for the diagnosis of the metabolic syndrome.”

   Nine words that almost never travel with the table they precede. The panel published a working definition, labelled it "for present purposes", and said in terms that it was not a standard. Two decades of pages have reproduced the table and dropped this line. If you have been told you meet "the criteria", this is the sentence to ask about.

3. The European definition makes the waist compulsory

   “According to the new IDF definition, for a person to be defined as having the metabolic syndrome they must have: Central obesity (defined as waist circumference* with ethnicity specific values) plus any two of the following four factors”

   This is the structural difference and it is larger than the numeric one. Under the IDF definition a man with a normal waist cannot have metabolic syndrome no matter how many of the other four he meets; under ATP III he can have it with three of them and a normal waist. The IDF also offers a shortcut for the measurement: "If BMI is >30kg/m², central obesity can be assumed and waist circumference does not need to be measured."

4. The ethnicity rule, which is about ancestry and not residence

   “ethnic group specific cut-points should be used for people of the same ethnic group wherever they are found. Thus the criteria recommended for Japan would also be used in expatriate Japanese communities, as would those for South Asian males and females regardless of place and country of residence.”

   A 12 cm difference between the Europid figure of 94 cm and the American ATP III figure of 102 cm, and a further 4 cm below that for South Asian, Chinese and Japanese men. The IDF also concedes in the same paragraph that "these are pragmatic cut-points taken from various different data sources and that better data will be needed to link these to risk" — they are administrative lines chosen from the data that existed, not measured risk boundaries, and the IDF says so.

5. How to measure the waist, if it is going to be measured at all

   “The waist measurement can be taken with a tape measure in a horizontal plane, midway between the inferior margin of the ribs and the superior border of the iliac crest.”

   Midway between the bottom rib and the top of the hip bone, tape horizontal. Not at the navel, which is where most people measure and which sits lower on most men — a systematically different number compared against a threshold that assumes the specified landmark. The IDF does say the measurement "can be done by people themselves", so this is one component a man can genuinely obtain; the threshold he compares it against is the part that needs someone else.

6. The 2009 attempt to unify, and what it left open

   “It was agreed that there should not be an obligatory component, but that waist measurement would continue to be a useful preliminary screening tool. Three abnormal findings out of 5 would qualify a person for the metabolic syndrome.”

   Six organisations met specifically to unify the criteria, and they succeeded on the structure: no obligatory component, three of five. On the number that actually separates the definitions, they did not — "A single set of cut points would be used for all components except waist circumference, for which further work is required. In the interim, national or regional cut points for waist circumference can be used." Seventeen years later the interim is still the position, which is why this page prints three columns rather than one.

7. And the argument that the diagnosis should not be made at all

   “Until much needed research is completed, clinicians should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the "metabolic syndrome."”

   Two of the largest diabetes organisations in the world, after an extensive review, telling clinicians to ignore the count. Their finding was that the syndrome "has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker". This is not a minority note appended to a consensus — it is one of the four positions this page prints, and it is the one that makes the practical point: act on each abnormal number whether or not three of them line up.

Where the guidelines disagree

On these points there is no consensus to report. Both positions are printed with the wording each body used.

The three published definitions, component by component

The same condition as three different documents define it, for a man. Read across a row before reading down a column: the disagreements are not rounding, and two of them change who has the diagnosis.

Four cells in the third column decline to print a number, and the reason is ours rather than the statement’s. The 2009 joint interim statement sits behind a publisher wall; we opened its abstract and not its tables. The abstract states that "It was agreed that there should not be an obligatory component" and that "A single set of cut points would be used for all components except waist circumference, for which further work is required. In the interim, national or regional cut points for waist circumference can be used." So we can print what was agreed structurally and we cannot print the four numeric values, and inventing them from a secondary source that reproduces the table would be exactly the kind of borrowing this site refuses. The first two columns come from documents we read in full. Sources: [1] [2] [3]

The IDF waist threshold for a man, by ancestry

Table 2 of the IDF consensus document, reproduced complete including the three groups for which the IDF states it has no data and tells you to borrow another group’s number. The IDF is explicit that these are ethnic-group specific and not country-of-residence specific.

Three things this table is not. It is not a measure of health at a given waist — the IDF says of its own numbers that "these are pragmatic cut-points taken from various different data sources and that better data will be needed to link these to risk". It is not about where you live: the guidance is that "ethnic group specific cut-points should be used for people of the same ethnic group wherever they are found". And it is not the American clinical practice, which the IDF itself notes in the first row is likely to go on using the ATP III figure of 102 cm. So the same man can be over the line in one clinic and under it in another, and neither clinic is doing anything wrong. Sources: [2]

What each body says about its own criteria

Read these four statements together before deciding how much weight to put on the diagnosis. Every one is from the organisation that wrote or reviewed the criteria, quoted from the document rather than characterised.

None of these is a fringe position and none is old news that a later consensus resolved — the harmonising statement is the later consensus, and it is the third row. What every body agrees on, including the two that doubt the syndrome exists as an entity, is that each of the five findings is worth acting on individually. That is the practical content of the page and it does not depend on the count. Sources: [1] [2] [3] [4]

Major causes of secondary dyslipidaemia, from ATP III

Table III.2–1 of the ATP III full report, reproduced complete. It matters here because a raised triglyceride and a low HDL are two of the five components, and these are the conditions and drugs that produce them without any syndrome being involved.

Anabolic steroids are on the list, named by the panel, which makes this table directly relevant to a substantial share of the men reading this site. ATP III’s own instruction is that "The family, drug, and diet history may reveal clues to secondary causes of dyslipidemia" and that history and examination "can provide clues to diabetes, hypothyroidism, nephrotic syndrome, or liver disease". A lipid panel counted into a five-point tally without that history has been counted too early. Sources: [1]

The tests, and what each one answers

What else produces these five numbers

A count of abnormal findings cannot tell you why they are abnormal, and several of the commonest reasons are separate diagnoses with their own treatments. ATP III makes the point directly about two of the five components: "The family, drug, and diet history may reveal clues to secondary causes of dyslipidemia", and history and examination "can provide clues to diabetes, hypothyroidism, nephrotic syndrome, or liver disease". Running the tally before running that history gets a label instead of an answer.

Type 2 diabetes that is already diagnosed

Under the IDF criteria "previously diagnosed type 2 diabetes" satisfies the glucose component outright, so a man with diabetes starts the count at one and frequently reaches three. The label adds something real — the IDF notes that people with type 2 diabetes who also have the syndrome "carry a much higher risk of CVD than those who have type 2 diabetes alone" — but it does not replace the diabetes diagnosis or its management, and confusing the two is common.

Hypothyroidism

Named on ATP III’s own list of major causes of secondary dyslipidaemia, and capable of producing a raised triglyceride and an unfavourable lipid pattern on its own. It is found with a thyroid-stimulating hormone measurement that no metabolic syndrome definition includes, which is exactly why the count has to come after the history rather than instead of it.

Anabolic steroid use

On ATP III’s list of drugs that may raise LDL cholesterol or cause other dyslipidaemias, alongside progestins, corticosteroids and HIV protease inhibitors. This one is directly relevant to a substantial share of men reading a men’s health site: a lipid panel drawn during or after a cycle can produce two of the five components from the drug rather than from any metabolic process, and a five-point tally will count them all the same.

Nephrotic syndrome, chronic renal failure and obstructive liver disease

Three more entries on ATP III’s secondary dyslipidaemia table, each of which is a serious diagnosis in its own right and each of which can move the lipid components. ATP III’s instruction when one is suspected is to investigate specifically — urinalysis for proteinuria, thyroid-stimulating hormone — rather than to interpret the lipids at face value.

Already-treated hypertension or dyslipidaemia

Not a competing diagnosis but a counting trap worth knowing about. The IDF criteria are satisfied by "treatment of previously diagnosed hypertension" and by "specific treatment for this lipid abnormality", so a man whose blood pressure and lipids are now well controlled on medication still meets those components. His count reflects his history rather than his present state, and a number that has been fixed is being counted as though it had not been.

Obesity without the rest of the cluster

A large waist alone is not this diagnosis under any of the three definitions — the IDF requires two further components and ATP III requires two others to make three. The reverse case is in ATP III’s own footnote: men at 94 to 102 cm, below the American line, "can develop multiple metabolic risk factors" and the panel says they should benefit from the same changes. Waist and syndrome are not interchangeable in either direction.

What treatment means here

Numbers this page will not give you

Each of these is a figure other pages state confidently. Each is omitted here because no source we could open supports one.

Do I have metabolic syndrome?

No total is computed anywhere on this page, because there is no single set of thresholds to compute it against. The three definitions printed above disagree about the waist number by 12 cm for a Europid man and by a further 4 cm for a South Asian, Chinese or Japanese man, disagree about whether the waist is obligatory, and disagree about the fasting glucose line by 10 mg/dL. The body convened in 2009 to resolve this settled the structure and left the waist threshold open, stating that "further work is required". A widget that produced a yes or a no would be concealing which definition it picked.

What are the harmonised 2009 cut points for triglycerides, HDL, blood pressure and glucose?

They are not printed here because we did not open the document that contains them. The 2009 joint interim statement is behind a publisher wall; its abstract is public and is quoted, and its abstract states only that a single set of cut points was agreed for those four components without giving them. Reproducing numbers from a secondary source that copies the table would mean citing a document we have not read, and the values would look identical to ones we had verified. The ATP III and IDF columns come from documents we read in full.

How common is metabolic syndrome?

No prevalence figure is given. Prevalence depends entirely on which definition is applied and to which population, and the three definitions on this page classify differently by design — the IDF’s own guidance is that "In future epidemiological studies of populations of Europid origin, prevalence should be given using both European and North American cut-points to allow better comparisons", which is a body telling researchers that one number is not reportable. Any single percentage you are quoted has a definition hidden inside it.

What is a normal or optimal fasting insulin, or HOMA-IR?

Nothing on this page states one, and the reason begins with the criteria themselves: ATP III "did not find adequate evidence to recommend routine measurement of insulin resistance (e.g., plasma insulin)" for this diagnosis, and the IDF says insulin resistance "is not an essential requirement" because it is difficult to measure in day-to-day clinical practice. Our HOMA-IR calculator refuses a single cut-off separately and for its own reasons, and this page does not contradict it.

How much does having metabolic syndrome raise my risk of a heart attack?

No multiplier is printed. The joint ADA/EASD review of exactly this question concluded that "there is considerable doubt regarding its value as a CVD risk marker", and the IDF itself records that the evidence on whether the cluster is worse than its parts is split: "Some studies have shown a purely additive risk whilst others show a greater interaction." A single risk figure would be picking one side of an unsettled question and dressing it as arithmetic.

Frequently asked questions

What are the criteria for metabolic syndrome?

There are at least three sets and they do not agree. ATP III (2001, United States): three or more of waist over 102 cm in a man, triglycerides ≥150 mg/dL, HDL under 40 mg/dL in a man, blood pressure ≥130/85 mmHg, and fasting glucose ≥110 mg/dL. IDF (2005–06, worldwide): central obesity is compulsory at ≥94 cm for a Europid man or ≥90 cm for a South Asian, Chinese or Japanese man, plus any two of triglycerides ≥150 mg/dL, HDL under 40 mg/dL, blood pressure ≥130/85 mmHg, or fasting glucose ≥100 mg/dL. The 2009 joint statement agreed there should be no obligatory component and that three of five qualify, and explicitly left the waist threshold unsettled. Worth knowing before any of that: ATP III’s own text says "There are no well-accepted criteria for the diagnosis of the metabolic syndrome."

What waist measurement counts as too big for a man?

It depends on which definition and, under one of them, on your ancestry. ATP III sets the line at over 102 cm (over 40 inches). The IDF sets it at ≥94 cm for Europid men and ≥90 cm for South Asian, Chinese and Japanese men, and says those are ethnic-group specific rather than country-of-residence specific — the South Asian figure applies to a South Asian man in Ohio. The IDF also concedes its numbers are "pragmatic cut-points taken from various different data sources" that need better data to link them to risk. The most useful line in either document is ATP III’s own footnote: men at 94 to 102 cm "can develop multiple metabolic risk factors" and should benefit from the same changes as men above the line.

Where exactly do I put the tape measure?

The IDF specifies it: "with a tape measure in a horizontal plane, midway between the inferior margin of the ribs and the superior border of the iliac crest" — midway between your lowest rib and the top of your hip bone, tape level all the way round. Not at the navel, which sits lower on most men and gives a systematically different number against a threshold that assumes the specified landmark. The IDF says the measurement itself "can be done by people themselves"; choosing which of the seven thresholds in its Table 2 to compare it against is the part that is not a home task.

Does having metabolic syndrome mean I will get diabetes or heart disease?

No figure is printed here, and that is a considered refusal rather than a dodge. The cluster is associated with both — that is why it was named. Whether the combination is worse than the sum of the components is disputed by the bodies themselves: the IDF writes that "Some studies have shown a purely additive risk whilst others show a greater interaction", and the joint ADA/EASD review found "considerable doubt regarding its value as a CVD risk marker". What is not disputed is that each component, on its own, is worth treating. If you want a number, the one to ask your clinician for is a formal cardiovascular risk estimate, which uses your actual values rather than a count of how many crossed a line.

Is metabolic syndrome even a real diagnosis?

It is a contested one, and a reader should know that before accepting the label. The joint statement from the American Diabetes Association and the European Association for the Study of Diabetes concluded after an extensive review that "the metabolic syndrome has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker", and advised that clinicians "should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria". The International Diabetes Federation takes the opposite view and published criteria "to clarify the nature of the syndrome and to focus therapeutic strategies". Both positions are printed on this page. Notice where they converge: the five numbers are what you act on either way.

Do I need a fasting insulin or a HOMA-IR to know whether I have it?

No. Neither is part of any of the three definitions, and both major panels said why. ATP III "did not find adequate evidence to recommend routine measurement of insulin resistance (e.g., plasma insulin), proinflammatory state (e.g., high-sensitivity C-reactive protein), or prothrombotic state (e.g., fibrinogen or PAI-1) in the diagnosis of the metabolic syndrome". The IDF says insulin resistance "is not an essential requirement" because it is difficult to measure in day-to-day clinical practice. That makes the syndrome named after insulin resistance one that is diagnosed without measuring it — and it is the reason our HOMA-IR calculator prints several published cut-offs rather than one.

Can anabolic steroids or TRT affect these numbers?

Anabolic steroids are named on ATP III’s own Table III.2–1 of major causes of secondary dyslipidaemia, alongside progestins, corticosteroids and HIV protease inhibitors. A lipid panel drawn during or shortly after use can therefore produce two of the five components — a raised triglyceride and a low HDL — from the drug rather than from any metabolic process, and a five-point tally counts them identically. ATP III’s own instruction is that "The family, drug, and diet history may reveal clues to secondary causes of dyslipidemia". Tell whoever is interpreting your panel what you are taking, before the count is run rather than after.

My blood pressure and cholesterol are controlled on medication — do they still count?

Yes, under the IDF definition, and this catches people out. The criteria are met by "treatment of previously diagnosed hypertension" and by "specific treatment for this lipid abnormality" as well as by the numbers themselves. So a man whose blood pressure is 118/74 on a tablet and whose triglycerides are 120 mg/dL on a statin still meets both components. His count is describing his history rather than his present state — which is defensible for a risk construct and misleading if you read it as a snapshot of how you are doing today.

Sources

1. [1]Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) — full report, NIH Publication 02-5215, hosted by NHLBI. Section II.6.b: "There are no well-accepted criteria for the diagnosis of the metabolic syndrome"; Table II.6-1 and its two footnotes; Table III.2-1, Major Causes of Secondary Dyslipidemia.
2. [2]The IDF consensus worldwide definition of the metabolic syndrome — International Diabetes Federation, 2006. Table 1 (the new IDF definition), Table 2 (ethnic specific values for waist circumference), and the "In practice" question-and-answer section on how central obesity is measured.
3. [3]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;120(16):1640–1645. PMID 19805654 — abstract only; the full text is behind a publisher wall and was not opened.
4. [4]Kahn R, Buse J, Ferrannini E, Stern M. 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;28(9):2289–2304. PMID 16123508 — the joint statement concluding that too much critically important information is missing to warrant designating the cluster a syndrome, and advising clinicians to treat every risk factor regardless of the criteria
5. [5]Alberti KG, Zimmet P, Shaw J. Metabolic syndrome — a new world-wide definition. A Consensus Statement from the International Diabetes Federation. Diabet Med. 2006;23(5):469–480. PMID 16681555 — the peer-reviewed publication of the IDF consensus, cited here for the IDF’s statement of its own purpose.