Encyclopedia entry

Ethnicity-adjusted BMI

The standard BMI thresholds (overweight 25+, obese 30+, severe obesity 40+) were derived from predominantly European-ancestry populations. NICE recommends a 2.5 kg/m² downward adjustment for South Asian, Chinese, Black African and African-Caribbean populations, reflecting evidence that metabolic and cardiovascular risk rises at lower BMI thresholds in those populations.

The adjusted thresholds

• · Overweight: 23+ (standard 25+).
• · Obese: 27.5+ (standard 30+).
• · Severe obesity: 32.5+ (standard 35+).
• · Highest severity: 37.5+ (standard 40+).

Why the adjustment exists

Multiple cohort studies (most notably Razak et al. 2007, Ntuk et al. 2014) showed that at any given BMI, South Asian populations carry more visceral adipose tissue, higher fasting glucose, and higher type 2 diabetes prevalence than European populations. Similar patterns are documented for Chinese, Black African and African-Caribbean populations. The 2.5 kg/m² adjustment is a calibration to align risk at threshold rather than BMI at threshold.

Why it matters for GLP-1 access

The NHS NICE TA1026 Mounjaro rollout uses ethnicity-adjusted BMI in each cohort definition. A patient from a South Asian background with BMI 32.5 qualifies for the cohort that requires BMI 35 in the general population. This is operationally important: the patient-facing NHS materials and many private clinics include ethnicity questions on the intake form for precisely this reason.

Important context

The ethnicity adjustment is a population-level calibration, not a precise individual measure. Body composition varies widely within any ethnic group. A waist circumference measurement, fasting glucose, HbA1c, and lipid profile are often more informative for individual risk than a BMI value, ethnicity-adjusted or otherwise. Your prescriber uses BMI as one input among several.

Related: NICE TA1026 · NHS GLP-1 access.