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Do I have obesity? Weight and health in the UK

What your BMI and waist-to-height ratio mean under NHS and NICE guidance, why some ethnic groups have lower thresholds, and which health problems the numbers point to.

GLP Guidebook teamUpdated 12 Oct 202610 min read25 sourcesWritten from published sources
The short answer

For most adults in the UK, a BMI of 25 to 29.9 counts as overweight and 30 or more as obesity. If your family background is South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean, the NHS uses lower numbers: 23 to 27.4 is overweight and 27.5 or more is obesity. Whatever your background, try to keep your waist under half your height.

Key facts

Overweight
BMI 25 to 29.9, or 23 to 27.4 for the ethnic groups above1
Obesity
BMI 30 or more, or 27.5 or more for the ethnic groups above1
Waist-to-height ratio
0.5 to 0.59 means increased health risk; 0.6 or more means higher risk. The same for everyone.1
How common (England)
29 in 100 adults live with obesity; 64 in 100 are overweight or living with obesity (2022)2
What 5–10% loss does
Lowers diabetes risk and improves blood sugar, blood pressure and liver fat3,4,5
What it doesn't decide
Whether you need a medicine. NHS rules for weight-loss medicines use their own, higher thresholds.6
On this page
  1. What are the UK thresholds, and why are some lower?
  2. How do I check my BMI and waist?
  3. When is BMI misleading?
  4. What are "clinical" and "pre-clinical" obesity?
  5. Which health problems are linked to extra weight?
  6. What does losing 5–10% of your weight do?
  7. Is obesity my fault?
  8. Questions people ask

What are the UK thresholds, and why are some lower?

NICE, which writes guidance for the NHS, uses lower BMI thresholds for some ethnic groups. People in these groups tend to carry more fat around the belly, and their risk of heart disease and diabetes starts at a lower BMI.1

BMI (body mass index) is your weight compared with your height. The WHO's global cut-offs call a BMI of 25 overweight and 30 obesity.7 In 2004, a WHO expert group found that many Asian people already face high diabetes and heart risk below 25.8 In 2022, NICE set lower thresholds for people with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background.1

What it meansMost adultsSouth Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background
Healthy weightBMI 18.5 to 24.91Below 23 (overweight starts at 23)1
OverweightBMI 25 to 29.91BMI 23 to 27.41
ObesityBMI 30 or more1BMI 27.5 or more1
Obesity class 2 and class 3From 35 and from 401Usually 2.5 lower: from 32.5 and from 37.51
Waist-to-height ratioUnder 0.5 is the healthy side1The same: under 0.51

The evidence behind it. A study of 1.5 million people in England looked at diabetes risk. South Asian people at a BMI of about 24 had the same risk as white people at a BMI of 30.9 Diabetes UK says people of Asian, Chinese, Black African and Black Caribbean ethnicity are two to four times more likely to have diabetes than white people.10 The NHS counts you at higher risk of type 2 diabetes from age 25 if you're from a South Asian, Chinese, Black African or Black Caribbean background, against age 40 if you're white.11

Why websites disagree. The NHS uses 27.5 as the obesity line for the groups above.12 Many US and global sites use 30 for everyone.7 Guidelines in India use 25 for people living there.13 They all agree that risk starts earlier for many people of Asian and Black heritage. See ethnicity and BMI in the UK or the India version of this guide.

How do I check my BMI and waist?

Put your numbers in below. You need scales, a tape measure and your height. Nothing you type leaves your device.

ftin
stlb
in

Your BMI and waist check appear here as you type. How to measure your waist

For adults 18 and over. It's a starting point, not a diagnosis: see when BMI is misleading. BMI bands and waist-to-height ratio from NICE1. Open the full checker (opens in a new tab) for teens, your healthy weight range and a summary to print.

Measuring your waist. NICE suggests this method:1

  • Find the bottom of your ribs and the top of your hips.
  • Wrap a tape measure around your waist halfway between the two. This is usually just above your belly button.
  • Breathe out naturally, then read the tape. Don't pull your stomach in.

Waist-to-height ratio. Divide your waist by your height, using the same units for both: both in inches, or both in cm.1 Under 0.5 is the healthy side of the line. 0.5 to 0.59 means increased health risk, and 0.6 or more means higher risk still. NICE uses this for adults with a BMI under 35, of both sexes and all ethnic groups.1 The NHS puts it simply: keep your waist to less than half your height.12

Work it out by hand

BMI is your weight in kg divided by your height in metres, squared.14 Worked example. Sam is 170 cm (5 ft 7 in, or 1.70 m) tall and weighs 84 kg (13 st 3 lb).

  • 1.70 × 1.70 = 2.89
  • 84 ÷ 2.89 = a BMI of about 29.1
  • For most adults, that is overweight. For someone from one of the ethnic groups above, it is in the obesity range, because that line is 27.5.1
  • Sam's waist is 96.5 cm (38 in). 96.5 ÷ 170 = 0.57, or in inches 38 ÷ 67 = 0.57. That is increased central fat (0.5 to 0.59).1
What to do with your result. NICE asks people with a BMI under 35 to check their own waist-to-height ratio, and to get advice from a health professional if it shows increased risk.1 Write down your numbers and take them to your GP practice. If you're 40 to 74 and have no existing health condition, you can ask your GP surgery or a local pharmacy for a free NHS Health Check.11 An HbA1c blood test shows your average blood sugar over the last 2 to 3 months, so ask whether you need one.15 Guide 6 covers seeing a doctor, and our doctor visit checklist (opens in a new tab) helps you prepare.

When is BMI misleading?

BMI can't tell fat from muscle, and it doesn't show where fat sits. So it's a starting point, not a diagnosis.1,16

  • Muscular people can get an "overweight" BMI without much body fat. NICE says to interpret BMI with caution in people with high muscle mass.1
  • People aged 65 and over: NICE says to interpret BMI with caution, partly because a slightly higher BMI may protect older people.1 Many also lose muscle with age, which BMI can't see.17,14
  • Pregnancy: adult BMI charts don't apply.18
  • Children and teens: adult cut-offs don't apply.18 A child's BMI is plotted on UK growth charts for their age and sex. NICE counts a child as overweight above the 91st centile (the line that 91 in 100 children of that age and sex sit below) and as having clinical obesity above the 98th centile.1 A GP, health visitor or school nurse can plot your child's numbers, or you can use the NHS healthy weight calculator.1
  • A "healthy" BMI with a large waist: NICE warns that someone with a healthy BMI may still carry too much fat around the middle. That is why it asks for waist-to-height ratio too.1

The 2025 Lancet Commission (a panel organised by the medical journal The Lancet Diabetes & Endocrinology) says BMI alone shouldn't be used to judge one person's health. It says to confirm extra fat with a second measure, like waist size.16

What are "clinical" and "pre-clinical" obesity?

They separate extra fat that is already harming your body from extra fat that isn't yet. The question is how your body is working, not just your weight.16

In January 2025, the Lancet Commission, a group of 58 experts, published a new definition. It has been endorsed by 76 organisations.16

  • Pre-clinical obesity: extra body fat, but your organs still work normally. Your risk of future illness is higher.16
  • Clinical obesity: extra fat is already affecting how your body works. Examples include breathlessness, or real limits on daily tasks like bathing or dressing.16
1Measure your BMI and waist
2Is there extra body fat? A high BMI plus a second measure, such as waist-to-height ratio, confirms it.
3Is the extra fat already affecting how your organs work, or limiting daily life?
NoPre-clinical obesityThe Commission advises health advice, regular check-ups and steps to lower the risk of future illness.
YesClinical obesityThe Commission advises timely treatment, chosen with a doctor after a full check-up.

Simplified from the 2025 Lancet Commission.16 This is an international definition. The NHS still uses the BMI and waist-to-height thresholds above to decide who gets which care.1,6

These numbers describe your health risk. They don't decide whether you need a medicine. Weight-loss medicines have their own rules. Their UK licences start at a BMI of 30, or 27 with a weight-related condition.19 NHS criteria are stricter: for example, NICE recommends tirzepatide (Mounjaro) from a BMI of 35 with at least one weight-related condition, and the NHS in England is rolling it out in stages.6,20 Treatment can mean many things, from food and activity changes to medicines or surgery.6 See your options and when a GLP-1 may or may not fit. You can also try our self-check: Could it be an option for me? (opens in a new tab)

Which health problems are linked to extra weight?

Extra body fat, especially around the belly, is linked to type 2 diabetes, heart disease, stroke, high blood pressure, some cancers, joint pain and fatty liver. The NHS says living with obesity is likely to shorten life by 2 to 10 years.12

The Health Survey for England measures adults' height, weight and waist every year. In 2022 it found:2

29%of adults in England living with obesity2
64%overweight or living with obesity2
~6Mpeople in the UK living with diabetes, about 1.3 million of them not yet diagnosed10
6.9Mat increased risk of type 2 diabetes, going by blood sugar10

The conditions, one by one

  • Type 2 diabetes and "prediabetes". An HbA1c blood test shows your average blood sugar over the last 2 to 3 months.15 In the UK it's given in mmol/mol, with the percentage beside it. 42 to 47 mmol/mol (6.0% to 6.4%) is called non-diabetic hyperglycaemia, which means a higher risk of diabetes.6 48 mmol/mol (6.5%) or more is in the diabetes range.21
  • High blood pressure and heart disease. Both are listed by the NHS as linked to obesity, and NICE lists them among conditions that can improve after weight-loss surgery.12,6
  • Fatty liver (MASLD). This is fat building up in the liver. Its new name is metabolic dysfunction-associated steatotic liver disease.22 It can improve with weight loss.6,5
  • Sleep apnoea. Breathing stops and starts during sleep. NICE lists it among conditions that can improve with weight loss after surgery.6
  • Joint pain from wear (osteoarthritis) and some cancers, including breast, womb and bowel cancer.12

What does losing 5–10% of your weight do?

For many people, losing 5–10% of body weight brings real health gains. For someone who weighs 90 kg (14 st 2 lb), that is about 4.5 to 9 kg (10 to 20 lb).4

These results come from food and activity programmes, not medicines.3,4,5,23

  • Less diabetes. In the US Diabetes Prevention Program, the lifestyle group aimed to lose at least 7% of their weight. Their diabetes rate was 4.8 per 100 people a year, against 11.0 on dummy pills (pills with no medicine in them), a 58% drop.3
  • Every kilo counts. In the same trial, each kg (about 2 lb) lost cut diabetes risk by 16%.24
  • It worked in the UK too. In the DiRECT trial in Scotland and England, people with type 2 diabetes followed a diet plan led by their GP practice. After a year, 1 in 4 had lost 15 kg (about 2 st 5 lb) or more, and almost half no longer had diabetes. Among those who lost 15 kg or more, 86 in 100 were free of it.23
  • Better sugar and blood pressure. One study looked at people with type 2 diabetes. Those who lost 5–10% of their weight had about 3.5 times the odds of their HbA1c falling by half a percentage point or more (for example, from 7.5% to 7.0%), compared with people whose weight stayed the same. Blood pressure and blood fats improved too.4
  • Less liver damage. One study followed 293 people with liver inflammation caused by fat. Of those who lost 5% or more, 58% saw it clear. Among those losing 10% or more, 90% did.5

Bigger weight losses generally brought bigger gains in these studies.4,5

Is obesity my fault?

No. Obesity is a long-term medical condition with many causes. It is not a lack of willpower.7,16

The WHO calls obesity a chronic disease. It comes from genes, brain signals, eating habits, access to healthy food, marketing and your surroundings.7 The Lancet Commission says blaming individuals isn't supported by the evidence.16

In 2020, experts from many countries signed a joint statement against weight stigma. They found it causes physical and mental harm.25 People who face it are also less likely to get proper care.25

NICE now asks health professionals to ask your permission before talking about your weight, and not to blame every symptom on it. If you come in with hip pain, for example, the hip pain should be dealt with first.1 The new name for fatty liver also dropped "fatty", which most experts surveyed found stigmatising.22

Questions people ask

My BMI is 28. Do I have obesity?

It depends on your background. For most adults, 28 is overweight. If your family background is South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean, the NHS counts 27.5 or more as obesity.1 Check your waist-to-height ratio too.1

My BMI is healthy, but my waist is large. Should I worry?

It's worth checking. NICE says someone with a healthy BMI can still carry too much fat around the middle. A waist-to-height ratio of 0.5 or more means increased health risk.1

Why does the NHS use lower numbers for some ethnic groups?

Because people from these groups tend to carry more fat around the belly, and their risk of heart disease and type 2 diabetes starts at a lower BMI.1,9 See the UK thresholds.

Which blood test shows my diabetes risk?

HbA1c, which shows your average blood sugar over the last 2 to 3 months.15 42 to 47 mmol/mol (6.0% to 6.4%) means a higher risk of type 2 diabetes.6 The ranges are under linked health problems.

Can I use these numbers for my child?

No. Adult cut-offs don't apply to children. Children's BMI is plotted on UK growth charts for their age and sex.18,1 See when BMI is misleading.

Does a high BMI mean I need a GLP-1 medicine?

No. BMI and waist describe risk. Medicines have their own licence rules, and NHS criteria are stricter still.19,6 Guide 3 and Guide 4 cover your options and when a medicine may or may not fit.

Before you move on

  • For most adults, BMI 25 is overweight and 30 is obesity.
  • For South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds, the lines are 23 and 27.5.
  • Keep your waist under half your height.
  • Clinical obesity means extra fat is already affecting your body.
  • Losing 5–10% of your weight can bring real health gains.
  • These numbers describe risk. They don't decide whether you need a medicine.
Your optionsShould I consider a GLP-1?Self-check quiz
Was this guide easy to understand?

Sources

  1. NICE. Overweight and obesity management (NG246), section "Identifying and assessing overweight, obesity and central adiposity", recommendations 1.8.1–1.10.10. Published 14 January 2025, last updated 8 January 2026. nice.org.uk
  2. NHS England Digital. Health Survey for England, 2022 Part 2: Adult overweight and obesity ("In 2022, 29% of adults were living with obesity, and 64% were overweight or living with obesity"). England only. digital.nhs.uk
  3. Knowler WC et al.; Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393–403. doi:10.1056/NEJMoa012512
  4. Wing RR et al.; Look AHEAD Research Group. Benefits of modest weight loss in improving cardiovascular risk factors in overweight and obese individuals with type 2 diabetes. Diabetes Care 2011;34:1481–6. doi:10.2337/dc10-2415
  5. Vilar-Gomez E et al. Weight loss through lifestyle modification significantly reduces features of nonalcoholic steatohepatitis. Gastroenterology 2015;149:367–78. doi:10.1053/j.gastro.2015.04.005
  6. NICE. Overweight and obesity management (NG246), section "Medicines and surgery", table 1 and recommendations 1.17–1.18 (including the definition of non-diabetic hyperglycaemia and box 2, conditions that can improve). nice.org.uk
  7. World Health Organization. Obesity and overweight (fact sheet). 8 December 2025. who.int
  8. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet 2004;363:157–63. doi:10.1016/S0140-6736(03)15268-3
  9. Caleyachetty R et al. Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study. Lancet Diabetes Endocrinol 2021;9:419–26. doi:10.1016/S2213-8587(21)00088-7
  10. Diabetes UK. How many people in the UK have diabetes? (estimates for 2024–25). Checked 12 October 2026. diabetes.org.uk
  11. NHS. Symptoms of type 2 diabetes and how it's diagnosed. Page last reviewed 10 February 2025. nhs.uk
  12. NHS. Obesity. Page last reviewed 29 April 2026. nhs.uk
  13. Misra A et al. Consensus statement for diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians. J Assoc Physicians India 2009;57:163–70 (Indian cut-offs, for people living in India). PMID 19582986
  14. US Centers for Disease Control and Prevention. About body mass index (BMI). Updated 16 December 2025. cdc.gov
  15. Diabetes UK. What is HbA1c? Checked 12 October 2026. diabetes.org.uk
  16. Rubino F et al. Definition and diagnostic criteria of clinical obesity (Lancet Diabetes & Endocrinology Commission). Lancet Diabetes Endocrinol 2025;13:221–62. The Commission had 58 members; 56 are named as authors. Declared interests: most of the 56 authors declare payments from Novo Nordisk, and many also from Eli Lilly (paper's own declaration). doi:10.1016/S2213-8587(24)00316-4
  17. Batsis JA, Villareal DT. Sarcopenic obesity in older adults: aetiology, epidemiology and treatment strategies. Nat Rev Endocrinol 2018;14:513–37. doi:10.1038/s41574-018-0062-9
  18. NHS. BMI calculator for adults: who it is not suitable for. nhs.uk
  19. Novo Nordisk. Wegovy 2.4 mg FlexTouch, summary of product characteristics (UK), section 4.1. Date of revision 09/2026. emc
  20. NICE. Tirzepatide for managing overweight and obesity (TA1026), 23 December 2024, including "What this means in practice" (phased NHS rollout in England). nice.org.uk
  21. American Diabetes Association. Diagnosis (A1C ranges: 6.5% or above is diabetes). diabetes.org
  22. Rinella ME et al. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Hepatology 2023. Declared interests: 21 of 53 authors declare consulting, advisory or grant ties to Novo Nordisk and 5 to Eli Lilly (paper's own declaration). doi:10.1097/HEP.0000000000000520
  23. Lean MEJ, Leslie WS, Barnes AC et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet 2018;391(10120):541–551. 306 people in Scotland and England. doi:10.1016/S0140-6736(17)33102-1
  24. Hamman RF et al. Effect of weight loss with lifestyle intervention on risk of diabetes. Diabetes Care 2006;29:2102–7. doi:10.2337/dc06-0560
  25. Rubino F et al. Joint international consensus statement for ending stigma of obesity. Nat Med 2020;26:485–97. Declared interests: 15 of 36 authors declare ties to Novo Nordisk and 2 to Eli Lilly; Novo Nordisk was one of the sponsors of the meeting's travel costs (paper's own declaration). doi:10.1038/s41591-020-0803-x

Last checked 12 Oct 2026 · Next review due Jan 2027 · Report an error

How this guide was made. Written by the GLP Guidebook team from the sources above: NICE and NHS guidance, national surveys and published trials. It's general information, not medical advice. Talk to your GP or another qualified health professional before starting, stopping or changing any treatment. In an emergency, call 999. For urgent help that isn't an emergency, use NHS 111 (in Northern Ireland, call your GP surgery for the out-of-hours service). How we write