Metabolic syndrome

What it is

Metabolic syndrome affects an estimated 19–25% of Canadian adults and approximately doubles the risk of cardiovascular disease and significantly raises the risk of type 2 diabetes. Also called syndrome X or insulin resistance syndrome, metabolic syndrome is not a single disease but a cluster of five metabolic risk factors that frequently occur together and amplify each other's harm in ways that exceed the sum of their individual effects.

A diagnosis requires three or more of the following five components to be present simultaneously:

Component	Threshold (men)	Threshold (women)
Waist circumference	≥ 102 cm (40 in)	≥ 88 cm (35 in)
Fasting triglycerides	≥ 1.7 mmol/L	≥ 1.7 mmol/L
HDL cholesterol	< 1.0 mmol/L	< 1.3 mmol/L
Blood pressure	≥ 130/85 mmHg	≥ 130/85 mmHg
Fasting glucose	≥ 5.6 mmol/L	≥ 5.6 mmol/L

These thresholds align with the 2009 harmonized international criteria published in Circulation (Alberti et al.) and are consistent with Diabetes Canada clinical practice guidelines. In Canada, routine metabolic screening is available through primary care, with fasting lipid panels and glucose testing processed at LifeLabs and Dynacare across most provinces.

Causes and mechanism

Insulin resistance is the central mechanism linking all five components. When cells in the liver, muscle, and fat tissue stop responding normally to insulin, a cascade follows:

Visceral fat accumulation — fat stored deep in the abdomen releases inflammatory cytokines and free fatty acids that directly impair insulin signalling in the liver and skeletal muscle. This is why waist circumference, not BMI alone, is the more clinically relevant measure.

Compensatory hyperinsulinaemia — the pancreas responds to insulin resistance by producing more insulin. Chronically elevated insulin promotes further fat storage, raises blood pressure through sodium retention and sympathetic nervous system activation, and in women stimulates ovarian androgen production — a key link to polycystic ovary syndrome (PCOS).

Chronic low-grade inflammation — visceral obesity sustains systemic inflammation that worsens insulin resistance and contributes independently to each of the five components.

Contributing factors include genetic predisposition, physical inactivity, a high-glycaemic low-fibre diet, obstructive sleep apnea, chronic psychological stress and elevated cortisol, and hormonal conditions such as PCOS, hypothyroidism, Cushing's syndrome, and growth hormone deficiency. Certain medications — antipsychotics and corticosteroids in particular — can also precipitate or worsen the syndrome.

Symptoms and diagnosis

Metabolic syndrome is largely asymptomatic. Most people have no noticeable symptoms until a complication such as type 2 diabetes or a cardiovascular event occurs. Occasionally, acanthosis nigricans (dark, velvety skin patches in body folds) is visible and signals underlying insulin resistance. Central or "apple-shaped" obesity with excess abdominal girth may be apparent on physical examination.

Diagnosis is made through clinical measurement and blood work:

1. Waist circumference
2. Blood pressure
3. Fasting lipid panel (triglycerides and HDL)
4. Fasting blood glucose

Where clinically indicated, additional tests include HbA1c, fasting insulin, HOMA-IR (a calculated index of insulin resistance), thyroid function, and liver enzymes to evaluate for non-alcoholic fatty liver disease.

Treatment options

Lifestyle intervention is the first-line treatment and targets insulin resistance directly.

Weight loss of 5–10% of body weight improves all five components meaningfully. Physical activity — at least 150 minutes per week of moderate aerobic exercise combined with resistance training — raises HDL, lowers triglycerides, and improves insulin sensitivity. A Mediterranean-style diet (vegetables, whole grains, legumes, fish, olive oil) has the strongest dietary evidence for improving metabolic syndrome components as a whole. Treating obstructive sleep apnea and reducing chronic stress both improve insulin signalling independently of weight change.

When lifestyle changes are insufficient, pharmacological treatment targets individual components:

• Metformin — insulin-sensitizing; reduces fasting glucose and lowers progression risk to type 2 diabetes
• Statins — for elevated LDL and overall cardiovascular risk reduction
• Fibrates or high-dose omega-3 fatty acids — for significantly elevated triglycerides
• ACE inhibitors or ARBs — for hypertension, with added kidney-protective effects
• GLP-1 receptor agonists (semaglutide, liraglutide) — reduce weight, blood sugar, blood pressure, and triglycerides simultaneously; increasingly used as a central treatment rather than an adjunct

Correcting underlying hormonal conditions — PCOS, hypothyroidism, Cushing's syndrome, growth hormone deficiency — directly improves metabolic syndrome components and should not be overlooked.

When to see a clinician in Canada

Request a metabolic screening assessment from your family physician or nurse practitioner if any of the following apply:

• Waist circumference above 88 cm (women) or 102 cm (men)
• A prior result showing elevated blood pressure, fasting glucose, or abnormal cholesterol
• Family history of type 2 diabetes or early cardiovascular disease
• Existing diagnosis of PCOS, non-alcoholic fatty liver disease, or sleep apnea
• Age 40 or older without a recent comprehensive metabolic health assessment

Most provincial health plans cover fasting glucose and lipid panel testing when ordered by a physician. Canadians without a family doctor can access metabolic screening through walk-in clinics, or through virtual care platforms such as Felix, Maple, Cleo, or Phoenix, which can order and interpret standard bloodwork.

Limitations and open questions

Research is still emerging on several aspects of metabolic syndrome. The diagnostic criteria themselves remain debated: some expert groups argue that waist circumference thresholds should be ethnicity-specific, as South Asian, East Asian, and Indigenous populations develop metabolic risk at lower waist measurements than the current universal cutoffs reflect. Health Canada and Diabetes Canada have not yet issued ethnicity-adjusted waist thresholds for routine clinical use in Canada, though some clinicians apply lower cutoffs informally.

The role of GLP-1 receptor agonists as a primary treatment for metabolic syndrome — rather than solely for type 2 diabetes or obesity — is an active area of investigation, and long-term outcome data in people without established diabetes are still accumulating. The optimal sequencing of lifestyle intervention versus pharmacotherapy, and whether reversing the syndrome fully eliminates residual cardiovascular risk, also remain open questions. Evidence on sex-specific differences in metabolic syndrome progression and treatment response is limited, particularly for transgender individuals on hormone therapy.