NICE CG189 BMI thresholds for South Asian, Chinese, Middle Eastern, Black African and African-Caribbean adults — and why

The biological reason: visceral adiposity and insulin resistance

Body Mass Index is a crude measure. It captures total body weight relative to height but tells you nothing about where the fat sits. Two adults with identical BMI of 28 can have very different metabolic risk: one with mostly subcutaneous fat (under the skin, mostly inert) and another with mostly visceral fat (around internal organs, metabolically active and inflammatory). For reasons that genetic and epidemiological studies have spent the last two decades unpacking, South Asian adults tend to deposit more visceral fat at a given BMI than white European adults. The fat-distribution pattern — often described as the 'thin-fat phenotype' — means that a South Asian adult at BMI 25 can have the metabolic profile of a European adult at BMI 30.

The INTERHEART study (Yusuf et al., Lancet 2004) was one of the largest case-control studies of myocardial infarction ever conducted. It showed that the risk of heart attack at any given BMI was significantly higher in South Asian populations than in European populations — and the risk rose at a lower BMI threshold. UK Biobank analyses have since confirmed the same pattern for type 2 diabetes: South Asian adults develop diabetes at BMI values around 4–6 units lower than white British adults.

The biology behind this includes lower lean muscle mass at a given weight, a tendency for adipocyte hypertrophy (large fat cells, which are more inflammatory) rather than hyperplasia (more small fat cells, which are less so), differences in the pancreatic beta-cell reserve, and genetic variants affecting lipid metabolism. None of this is anyone's 'fault' — it's the population biology, and it has to be respected when we set clinical thresholds.

NICE CG189 in detail

NICE Clinical Guideline 189 (Obesity: identification, assessment and management) was first published in 2014 and has been updated periodically since. The relevant section is the recommendation that, for adults of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family origin, the BMI thresholds used to identify weight-related health risk should be reduced by 2.5 points across the categories:

• 'Healthy weight' upper limit: 25 reduced to 23
• 'Overweight' upper limit: 30 reduced to 27.5
• 'Obesity class 1' upper limit: 35 reduced to 32.5
• 'Obesity class 2' upper limit: 40 reduced to 37.5

NICE based the recommendation on a synthesis of cardiovascular and diabetes risk evidence specific to these populations. It mirrors a similar World Health Organization position from 2004 specifically for Asian populations, and similar thresholds used in India, Hong Kong and Singapore.

What this means for GLP-1 eligibility

The NICE technology appraisals for Wegovy (TA875) and Mounjaro (TA1026) reference CG189. So the threshold reductions apply directly to who qualifies for these treatments — both on the NHS and, importantly, as a clinically appropriate justification in private prescribing.

• BMI 27.5 with a weight-related comorbidity (T2D, hypertension, dyslipidaemia, OSA, NAFLD) replaces BMI 30 with comorbidity
• BMI 25 with comorbidity, in specialist settings, replaces BMI 27.5 with comorbidity
• BMI 32.5 unconditional replaces BMI 35 unconditional

Practically, this matters a lot in our Rusholme weight-loss clinic. Many of our patients there have a BMI in the 27–30 range, would not qualify under standard NHS criteria, but absolutely qualify under CG189 because they're South Asian and have insulin resistance, prediabetes (HbA1c 42–47), or hypertension. The same applies for our patients across Manchester from Chinese, Middle Eastern, African and African-Caribbean backgrounds.

Which exact populations are covered

NICE CG189 uses 'family origin' rather than nationality. It applies to adults of:

• South Asian: Indian, Pakistani, Bangladeshi, Sri Lankan, Nepalese
• Chinese: Han Chinese and the wider Chinese diaspora
• Other Asian: Filipino, Indonesian, Malaysian, Thai, Vietnamese, Korean, Japanese
• Middle Eastern: Including but not limited to Arab, Iranian, Turkish, Kurdish
• Black African: Nigerian, Ghanaian, Somali, Sudanese, Ethiopian and others
• African-Caribbean: Jamaican, Bajan, Trinidadian and other Caribbean origin

For people of mixed family origin, clinical judgement applies — we'd typically apply the lower threshold if at least one parent comes from a covered population, but discuss this with the patient.

Why GPs don't always apply this consistently

The honest answer: time and awareness. In a 10-minute GP appointment, BMI is calculated from the standard table, and the ethnicity adjustment is easy to overlook — especially when the GP didn't write CG189 and isn't reminded of it on the screen. Some practices' computer templates flag the adjustment automatically; many don't. There's no malice in this; it's a workflow gap.

The result is that South Asian and other minority patients are systematically under-treated for obesity-related metabolic disease. They're told their BMI is 'borderline' and to lose weight, but not offered the same access to pharmacological support that a white European at the same metabolic risk would receive. We see this regularly. At Trafford Clinic, we calculate the ethnicity-adjusted BMI category as part of our initial assessment for every patient who comes to us for weight management, and we make the GLP-1 eligibility recommendation accordingly.

Worked examples

Example 1: Mrs A, 45, Pakistani-British, height 158cm, weight 70kg. BMI 28.0. HbA1c 44 mmol/mol (prediabetes), blood pressure 142/88. Standard BMI category: overweight. Under CG189: obesity class 1 equivalent (above the 27.5 threshold). She qualifies for GLP-1 treatment with prediabetes as the comorbidity.

Example 2: Mr B, 38, Black African-British, height 175cm, weight 92kg. BMI 30.0. No comorbidities. Standard category: obesity class 1. Under CG189: equivalent to obesity class 2 (above the 32.5 threshold actually no — 30 is between 27.5 and 32.5). So obesity class 1 under CG189. He'd qualify for GLP-1 only with a comorbidity, but the threshold is met.

Example 3: Ms C, 29, Chinese-British, height 165cm, weight 71kg. BMI 26.0. NAFLD on ultrasound, raised ALT. Standard category: overweight. Under CG189: just over the 25 healthy-weight cap — so 'overweight' under the adjusted scale too. Borderline. We'd consider GLP-1 in a specialist setting given the established NAFLD.

The blood-tests companion piece

For any patient borderline on BMI, we run a baseline blood panel before considering GLP-1: HbA1c, lipid profile, liver function, thyroid, vitamin D, B12. The panel is the same for all ethnicities but the threshold of concern for HbA1c and lipids can be tighter for higher-risk populations. See our Rusholme blood tests page and our Manchester blood tests page. The companion reading blood test results guide covers what each marker means.

Vitamin D deficiency is especially common in South Asian and Middle Eastern populations — see our Manchester vitamin D guide. B12 deficiency is also common, particularly with metformin use; see our Rusholme B12 page.

How to book

If you've been told your BMI is 'borderline' but you have risk factors — prediabetes, hypertension, fatty liver, family history of T2D, polycystic ovary syndrome — it's worth a conversation. We assess everyone individually using ethnicity-adjusted thresholds. Book at traffordclinic.co.uk/weight-loss or call 0161 258 6149. We're at 122 Seymour Grove, Old Trafford, with patients regularly travelling from Rusholme, Longsight, Cheetham Hill and across south Manchester.

Related reading: Mounjaro vs Wegovy, Pre-Mounjaro baseline panel.