What is a Metabolic Risk Score?

A Metabolic Risk Score (0–100) aggregates multiple body composition and metabolic markers into a single number. It draws on BMI, Waist-to-Height Ratio, Body Roundness Index, ABSI, and (optionally) blood biomarkers like TyG Index and HOMA-IR. Higher scores indicate greater cardiometabolic risk regardless of weight category.

What is the Body Roundness Index (BRI)?

BRI (Body Roundness Index) was developed by Thomas et al. (2013) to estimate body fat percentage and visceral fat from height and waist circumference alone. It uses an ellipse model: BRI = 364.2 − 365.5 × √(1 − (WC/2π)² / (0.5×H)²). Values above 4.5 indicate elevated visceral fat risk.

What is the TyG Index?

The Triglyceride-Glucose (TyG) Index = ln(Triglycerides mg/dL × Fasting Glucose mg/dL / 2). It is a validated surrogate for insulin resistance requiring only two standard blood panel values. Values ≥8.5 indicate insulin resistance. Validated by Smith et al. (JAMA Network Open, 2019) with r=0.77 correlation to HOMA-IR.

HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) = (Fasting Insulin µU/mL × Fasting Glucose mg/dL) / 405. It is the clinical gold standard for insulin resistance estimation. Normal: 2.5. Significant IR: >3.5. Requires a fasting insulin blood test.

What is 'Skinny Fat' or Normal Weight Obesity?

Normal Weight Obesity (NWO), colloquially 'skinny fat', describes individuals with normal BMI (18.5–24.9) but metabolically unhealthy profiles — high visceral fat, insulin resistance, dyslipidaemia. Romero-Corral et al. (2008) found ~24% of normal-BMI US adults are metabolically unhealthy (MUHNW phenotype).

ABSI (A Body Shape Index) = WC / (BMI^(2/3) × H^(1/2)). Developed by Krakauer & Krakauer (2012), ABSI isolates waist circumference as an independent mortality risk factor beyond BMI and height. Higher ABSI is associated with increased all-cause mortality risk independent of overall weight.

What are the 4 metabolic phenotypes?

(1) MHNW: Metabolically Healthy Normal Weight — normal BMI, healthy metabolic profile. (2) MUHNW: Metabolically Unhealthy Normal Weight — normal BMI, insulin resistance and/or dyslipidaemia ('skinny fat'). (3) MHO: Metabolically Healthy Obese — elevated BMI but healthy metabolic markers. (4) MUHO: Metabolically Unhealthy Obese — elevated BMI and metabolic dysfunction. Source: Wildman et al., Arch Intern Med (2008).

Metabolic Health Calculator – BRI, ABSI & TyG Index

TIER 1 Body Measurements — No blood test required

Height (cm)

Weight (kg)

Waist Circumference (cm)

Age (years)

Sex

Systolic Blood Pressure (mmHg) optional

// The Science

Why Normal BMI Doesn't Mean Metabolically Healthy

The 4 Metabolic Phenotypes

Wildman et al. (2008) analysed 5,440 US adults (NHANES III) and found that 23.5% of normal-weight adults were metabolically unhealthy — with ≥2 of: elevated fasting glucose, triglycerides, blood pressure, CRP, or low HDL. Meanwhile, 31.7% of overweight/obese adults were metabolically healthy.

The implication: cardiovascular risk tracks metabolic health more closely than BMI. A "normal" BMI is not a metabolic health clearance.

Body Shape vs. Body Size

Visceral adipose tissue (VAT) — fat surrounding the abdominal organs — is metabolically active and drives inflammation, insulin resistance, and dyslipidaemia. VAT is poorly estimated by BMI.

BRI and ABSI both use waist circumference to better capture VAT than BMI. A large Tobias et al. (2014) review in Int J Obesity confirmed WHtR outperforms BMI for metabolic syndrome prediction.

TyG: Insulin Resistance From a Routine Blood Panel

Insulin resistance is the central driver of type 2 diabetes, NAFLD, and cardiovascular disease. The gold standard test (HOMA-IR) requires fasting insulin, which is not on most routine panels.

The TyG Index (ln[TG × Glucose / 2]) requires only triglycerides and fasting glucose — both on standard panels — and correlates at r=0.77 with HOMA-IR across populations (Simental-Mendía et al., 2008; Smith et al., 2019).

// Methodology & References

Formula & Calculation Method

Body Roundness Index (BRI)

BRI = 364.2 − 365.5 × √(1 − (WC/2π)² / (0.5×H)²)

WC — Waist circumference in metres
H — Height in metres

Source: Thomas et al., PLOS ONE (2013). BRI >4.5: elevated visceral fat risk.

ABSI (A Body Shape Index)

ABSI = WC / (BMI^(2/3) × H^(1/2))

WC — Waist circumference in metres
BMI — Body Mass Index kg/m²
H — Height in metres

Source: Krakauer & Krakauer, PLOS ONE (2012). Normalised to age/sex z-score for risk interpretation.

Body Fat % (Deurenberg)

BF% = 1.2×BMI + 0.23×Age − 10.8×Sex − 5.4

Sex — 1 = male, 0 = female
Age — Years

Source: Deurenberg et al., Br J Nutrition (1991). Validated across European populations; ±3–4% accuracy.

TyG Index

TyG = ln(Triglycerides × Glucose / 2)

Triglycerides — mg/dL
Glucose — Fasting glucose mg/dL

Source: Simental-Mendía et al. (2008); Smith et al., JAMA Network Open (2019). Threshold ≥8.5 = insulin resistance.

HOMA-IR

HOMA-IR = (Insulin × Glucose) / 405

Insulin — Fasting insulin in µU/mL
Glucose — Fasting glucose in mg/dL

Source: Matthews et al., Diabetologia (1985). Normal <1.0; IR >2.5; significant IR >3.5.

Authoritative Sources & Standards

Romero-Corral et al. (2008): "Accuracy of body mass index in diagnosing obesity in the adult general population." Int J Obesity 32:959–966. NHANES data showing 20–30% BMI misclassification. → PubMed
Wildman et al. (2008): "The obese without cardiometabolic risk factor clustering and the normal weight with cardiometabolic risk factor clustering." Arch Intern Med 168(15):1617–1624. The 4-phenotype classification. → PubMed
Thomas et al. (2013): "Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model." PLOS ONE 8(7). BRI formula and validation. → PubMed
Krakauer & Krakauer (2012): "A new body shape index predicts mortality hazard independently of body mass index." PLOS ONE 7(7). ABSI derivation and mortality association. → PubMed
Smith et al. (2019): "Triglyceride-glucose index as a marker of insulin resistance: a systematic review." JAMA Network Open. TyG vs HOMA-IR correlation r=0.77. → PubMed
Tobias et al. (2014): "Body-mass index and waist-circumference cutoffs." Int J Obesity. WHtR outperforms BMI for metabolic syndrome prediction. → PubMed
Ashwell, Gunn & Gibson (2012): "Waist-to-height ratio is a better screening tool than waist circumference." Obesity Reviews 13(3):275–286. Meta-analysis of 31 studies, 300,000+ participants. → PubMed
Matthews et al. (1985): "Homeostasis model assessment." Diabetologia 28(7):412–419. Original HOMA-IR derivation. → PubMed
NCEP ATP III (2001, updated 2005): Metabolic Syndrome criteria: ≥3 of: abdominal obesity, elevated triglycerides, low HDL, elevated blood pressure, elevated fasting glucose. → NIH

Expert Insights

"Normal-weight individuals with metabolic abnormalities had a similar or greater risk of death compared with obese individuals without metabolic abnormalities. Metabolic health status is a stronger predictor of mortality than weight status."

— Wildman et al., Archives of Internal Medicine (2008)

"The TyG index is a simple, inexpensive, and reliable surrogate marker of insulin resistance that can be measured in most clinical and epidemiological settings where fasting insulin is unavailable."

— Simental-Mendía et al., Cardiology Journal (2008)

// Common Questions

Frequently Asked Questions

A composite score (0–100) aggregating body composition and metabolic markers. Tier 1 (body measurements only) weights BMI, WHtR, BRI, and ABSI. Adding blood values (Tier 2/3) improves accuracy significantly. It is not a clinical diagnostic — use it as a screening and tracking tool.

BRI uses height and waist circumference to model the body as an ellipse and estimate visceral adiposity. Developed by Thomas et al. (2013), it correlates better with visceral fat than BMI. Values: <3.0 lean, 3.0–4.5 normal, 4.5–6.0 elevated, >6.0 high visceral fat risk.

TyG = ln(Triglycerides mg/dL × Fasting Glucose mg/dL / 2). A validated surrogate for insulin resistance. Values: <8.0 normal, 8.0–8.5 borderline, ≥8.5 insulin resistant. Available from any standard blood panel — no fasting insulin test required.

HOMA-IR = (Fasting Insulin × Fasting Glucose) / 405. Normal: <1.0. Early insulin resistance: 1.0–2.5. Significant resistance: >2.5. Severe: >3.5. It requires a fasting insulin blood test, not part of standard panels — ask your GP specifically.

Normal Weight Obesity (NWO) or Metabolically Unhealthy Normal Weight (MUHNW): normal BMI (18.5–24.9) with metabolic dysfunction — elevated visceral fat, insulin resistance, and/or dyslipidaemia. Prevalence: ~24% of normal-BMI US adults (Romero-Corral et al., 2008). Associated with same cardiovascular risk as obesity.

ABSI (A Body Shape Index) = WC / (BMI^(2/3) × H^(1/2)). It isolates waist circumference as an independent mortality predictor. Higher ABSI z-score indicates greater risk. Krakauer & Krakauer (2012) showed a 1 standard deviation increase in ABSI is associated with 13–18% increased mortality hazard.

NCEP ATP III defines metabolic syndrome as ≥3 of: (1) Waist >102 cm (M) / >88 cm (F); (2) Triglycerides ≥150 mg/dL; (3) HDL <40 mg/dL (M) / <50 mg/dL (F); (4) Blood pressure ≥130/85 mmHg; (5) Fasting glucose ≥100 mg/dL.

Yes. Evidence-based interventions with strongest metabolic impact: (1) Resistance training — increases insulin sensitivity by 20–30% (Colberg et al., Diabetes Care, 2010); (2) Zone 2 cardio (150 min/week) — reduces triglycerides and visceral fat; (3) Reduced refined carbohydrates — lowers TyG index; (4) 7–9 hours sleep — poor sleep raises fasting glucose and cortisol; (5) Waist reduction of 5–10 cm can shift metabolic phenotype.

// Explore More