Lower BMI Thresholds for South Asian, Chinese, Black African and Caribbean People

In the UK, NICE recommends lower BMI thresholds for people of South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean family background. For these groups, a BMI of 27.5 or more is used as a practical threshold for obesity (instead of 30), and higher thresholds such as 35 and 40 are usually reduced by 2.5. The reason is that people from these backgrounds tend to develop type 2 diabetes and other weight-related conditions at a lower BMI. These adjusted thresholds apply to NHS eligibility for weight loss injections such as Wegovy and Mounjaro, including the phased NHS Mounjaro roll-out. This guide explains the evidence and what it means for you.

The lower thresholds at a glance

These thresholds come from NICE guideline NG246 on overweight and obesity management, which brought together earlier NICE recommendations, including public health guidance PH46 published in 2013. You can check your BMI with our BMI calculator, and our guide to BMI and treatment eligibility explains how BMI works more generally.

Why lower thresholds are used

Different risk at the same BMI

BMI was developed largely using data from people of European ancestry. Over time, research has shown that the relationship between BMI and health risk differs between populations. At the same BMI, people from some ethnic backgrounds have a higher risk of:

• type 2 diabetes
• high blood pressure
• abnormal blood fats
• cardiovascular disease

The difference is most pronounced for type 2 diabetes. In the UK, type 2 diabetes is considerably more common among people of South Asian, Black African and African-Caribbean background than among White Europeans, and it tends to develop at a younger age.

The role of body fat distribution

One explanation is how and where the body stores fat. On average, people of South Asian background tend to have a higher proportion of body fat at a given BMI, and more fat stored around the abdomen and internal organs (visceral fat). Visceral fat is more metabolically active and more closely linked to insulin resistance than fat stored under the skin elsewhere.

The picture for people of Black African and African-Caribbean background is more complex. Studies suggest they may, on average, have less visceral fat than White Europeans at the same BMI, but still a higher risk of type 2 diabetes, possibly because of differences in insulin secretion and sensitivity. This shows that fat distribution is not the whole story, and genetic, environmental and social factors all play a part.

Social and structural factors

Differences in health risk are not only biological. Socioeconomic deprivation, access to healthy food and safe spaces for activity, experiences of discrimination, and access to healthcare all influence weight and health outcomes, and these factors are unequally distributed across ethnic groups in the UK. Lower BMI thresholds aim to make clinical criteria fairer, but they do not address these wider inequalities on their own.

The evidence behind the thresholds

WHO expert consultation (2004)

In 2004, a World Health Organization expert consultation, published in The Lancet, reviewed evidence on BMI and health risk in Asian populations. It concluded that many Asian populations had a substantial risk of type 2 diabetes and cardiovascular disease at BMIs below the standard overweight cut-off of 25, and proposed additional "action points" for public health, including 23 and 27.5. These figures underpin the thresholds NICE uses today.

NICE PH46 (2013)

NICE public health guidance PH46 recommended using lower BMI thresholds (23 and 27.5) as triggers for action to prevent type 2 diabetes in Black, Asian and other minority ethnic groups. It acknowledged that evidence was stronger for South Asian and Chinese populations than for some other groups, but recommended a pragmatic approach.

English cohort study (2021)

A large population-based study published in The Lancet Diabetes & Endocrinology in 2021 used GP records from England to estimate, for different ethnic groups, the BMI that carried the same risk of type 2 diabetes as a BMI of 30 in White adults. The equivalent BMIs were considerably lower for several groups:

These findings supported using lower thresholds, and suggested that for South Asian people the true equivalent may be even lower than 27.5. NICE's thresholds represent a practical, single adjustment rather than a precise value for every group.

How the thresholds affect eligibility for weight loss injections

NHS: Wegovy (semaglutide)

NICE TA875 recommends semaglutide within specialist weight management services for adults with at least one weight-related condition and a BMI of at least 35, or 30 to 34.9 if they meet criteria for referral to specialist services. It advises using a lower BMI threshold, usually reduced by 2.5 kg/m², for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background. See Wegovy on the NHS.

NHS: Mounjaro (tirzepatide)

NICE TA1026 recommends tirzepatide for adults with a BMI of at least 35 and at least one weight-related condition, with a lower threshold (usually reduced by 2.5) for the same groups. NHS England's interim commissioning guidance for the phased roll-out also adjusts BMI for ethnicity:

The five qualifying conditions are type 2 diabetes, high blood pressure, heart disease, obstructive sleep apnoea and abnormal blood fats. See Mounjaro on the NHS.

NHS: bariatric surgery

NICE NG246 also recommends reducing BMI thresholds by 2.5 kg/m² for these groups when considering referral for bariatric surgery, including for expedited assessment in people with recent-onset type 2 diabetes. See GLP-1 medication vs bariatric surgery.

NHS lifestyle programmes

Lower thresholds are also used for some NHS lifestyle programmes. For example, the NHS Digital Weight Management Programme uses a lower BMI threshold of 27.5 for people from these ethnic groups who have diabetes or high blood pressure.

Private treatment

The UK licences for Mounjaro and Wegovy, set out in their Summaries of Product Characteristics, use standard thresholds: a BMI of 30 or more, or 27 to 30 with at least one weight-related condition. They do not themselves set separate ethnicity-adjusted thresholds.

In practice, this means:

• For someone from one of these groups with a BMI of 27 to 30 and a weight-related condition, treatment may be within the licence.
• For someone with a BMI below 27, or 27 to 30 without a weight-related condition, prescribing would generally fall outside the licensed criteria, even though NICE would classify a BMI of 27.5 as obesity for that person.

Private providers vary in their policies. Ask any provider how they assess eligibility and how they take ethnicity into account. A prescriber may also consider your waist-to-height ratio and other risk factors in judging whether treatment is appropriate. See who can get weight loss injections and private vs NHS weight loss treatment.

Worked examples

These examples show how the thresholds work in principle. They are illustrations, not predictions of any individual prescribing decision.

Waist-to-height ratio: a useful extra check

NICE recommends measuring waist-to-height ratio alongside BMI in adults with a BMI under 35. It is particularly helpful for people whose risk may be underestimated by BMI, including many people from the ethnic groups discussed here.

To calculate it, divide your waist measurement (taken midway between your lowest rib and the top of your hip bone) by your height, in the same units.

A simple rule is to keep your waist to less than half your height. Waist-to-height ratio does not change licensed criteria, but it can help you and your clinician understand your risk.

Type 2 diabetes: why early action matters

Because type 2 diabetes tends to develop at lower BMIs and younger ages in these groups, early identification of risk is important. NICE recommends that people from these backgrounds are offered diabetes risk assessment, and the NHS Health Check (for adults aged 40 to 74 in England) includes diabetes risk screening.

If you have prediabetes (raised blood sugar that is not yet in the diabetes range), the NHS Diabetes Prevention Programme may be available. For people who already have type 2 diabetes, weight loss can improve blood sugar control and, for some, lead to remission. GLP-1 medicines can play a role in diabetes care as well as weight management. See GLP-1s and type 2 diabetes.

How ethnicity is recorded and used in practice

In NHS records

Your GP record usually includes an ethnicity code, which you will often have been asked about when registering with a practice. Ethnicity is self-reported: it is how you describe your own background, not something a clinician decides. If your record is missing this information, or if it is incorrect, you can ask your practice to update it. This matters because some NHS systems use ethnicity, along with BMI and diagnoses, to identify people who may be eligible for programmes or for the phased Mounjaro roll-out.

In consultations

A GP or prescriber may ask about your family background as part of assessing your risk. You do not have to share this information, but doing so can help make sure the right thresholds and risk assessments are used. It can also be helpful to mention:

• whether parents, brothers or sisters have type 2 diabetes, heart disease or stroke, and at what age
• whether you had gestational diabetes in a previous pregnancy
• any history of polycystic ovary syndrome (PCOS), which is linked to insulin resistance
• previous blood test results showing raised blood sugar or cholesterol

Questions you might ask

• Which BMI thresholds apply to me, given my background?
• Do I meet the criteria for any NHS weight management programmes?
• Am I likely to be eligible for NHS Mounjaro now or in a later cohort?
• Should I have my blood sugar (HbA1c), blood pressure or cholesterol checked?
• What is my waist-to-height ratio, and what does it mean for my risk?

Medicines are not the only option

Lower thresholds can bring more people into scope for treatment, but medicines are only one part of managing weight-related risk. For many people, especially those near the overweight threshold, the first steps are lifestyle-based:

• Diet: NHS dietary advice, culturally relevant healthy eating resources and, where available, NHS lifestyle programmes. Traditional diets vary widely, and a dietitian can help adapt advice to the foods you eat.
• Physical activity: the UK Chief Medical Officers recommend at least 150 minutes of moderate activity a week for adults, plus strength activities on at least two days.
• Sleep and stress: both affect appetite and blood sugar.
• Diabetes prevention: if you have prediabetes, the NHS Diabetes Prevention Programme offers structured support.

Where medication is appropriate, GLP-1 medicines have been studied in trials that included participants from a range of ethnic backgrounds, although Asian and Black participants have often been under-represented relative to their risk. Trials such as SURMOUNT-1 (tirzepatide) and STEP 1 (semaglutide) reported weight loss across subgroups, but individual response varies regardless of background. See what are GLP-1 medications and realistic weight loss expectations.

Limitations and ongoing debate

Ethnicity-adjusted thresholds are widely supported, but they are not perfect:

• Broad categories. Groupings such as "South Asian" or "Black African" include diverse populations with different risks.
• Uneven evidence. Evidence is stronger for some groups, such as South Asian populations, than others.
• Single adjustment. A uniform reduction of 2.5 may underestimate risk in some groups (as the 2021 English study suggested for South Asian people) and overestimate it in others.
• Mixed heritage. There is no precise rule for people of mixed heritage, so clinical judgement is needed.
• Beyond BMI. Many experts argue that measures of central fat and actual health status should play a bigger role. A 2025 Lancet Diabetes & Endocrinology Commission proposed defining "clinical obesity" based on evidence of illness or functional limitation, not size alone.

Despite these limitations, lower thresholds are an important step towards fairer access to prevention and treatment.

What to do next

1. Check your BMI and waist-to-height ratio. Use our BMI calculator and a tape measure.
2. Try our eligibility checker, which takes ethnicity into account for NHS criteria. It is informational only.
3. Talk to your GP. Tell them about your family background and any family history of type 2 diabetes or heart disease. Ask about NHS Health Checks, diabetes screening and NHS weight management options.
4. If considering private treatment, ask providers how they assess eligibility. Compare regulated services on our providers page and see what affects cost on our prices page.

For an overview of the medicines, see weight loss injections and every UK weight loss injection compared.

When to speak to a professional

Speak to your GP if your BMI or waist-to-height ratio is above the thresholds for your background, if you have a family history of type 2 diabetes or heart disease, or if you have symptoms that could suggest diabetes, such as feeling very thirsty, passing urine more often (especially at night), unexplained tiredness, blurred vision, slow-healing cuts or unexplained weight loss.

If you are taking a weight loss medicine, seek urgent medical help (NHS 111, or 999 in an emergency) if you experience:

• severe, persistent abdominal pain, possibly spreading to your back, with or without vomiting (possible pancreatitis)
• pain in the upper right abdomen, fever, or yellowing of the skin or eyes (possible gallbladder problems)
• persistent vomiting or diarrhoea with signs of dehydration
• swelling of the face, lips or throat, or difficulty breathing
• symptoms of low blood sugar if you take diabetes medicines, such as shaking, sweating or confusion