Why Asian and Black adults use a lower BMI threshold
BMI was built on data from white European populations, and it treats every body the same way: weight against height, nothing more. Decades of research since have shown that body fat behaves differently across ethnic groups. At an identical BMI, South Asian adults typically carry more visceral fat — the fat that wraps around the liver and pancreas — and proportionally less muscle. Black African and African-Caribbean adults show a similar earlier rise in blood pressure and type 2 diabetes risk.
The practical result is that the health risk a white European faces at a BMI of 25 arrives around a BMI of 23 for these groups, and the risk seen at 30 arrives around 27.5. NICE and the NHS therefore recommend the lower thresholds, and this calculator applies them the moment you flip the toggle.
BMI chart: standard vs Asian and Black thresholds
| Category | White / other | Asian, Black African & African-Caribbean |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Healthy weight | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25 – 29.9 | 23 – 27.4 |
| Obesity class I | 30 – 34.9 | 27.5 – 32.4 |
| Obesity class II | 35 – 39.9 | 32.5 – 37.4 |
| Obesity class III | 40 and above | 37.5 and above |
How BMI is calculated
Metric: weight in kilograms divided by height in metres squared. Imperial: weight in pounds divided by height in inches squared, then multiplied by 703. The calculator above also converts your healthy BMI range back into an actual weight range in kilograms and pounds, which is far more useful than a bare number.
What BMI misses — and what to check instead
- Waist to height ratio. Keep your waist under half your height. It catches central fat that BMI cannot see, and it works across ethnicities.
- Muscle mass. Rugby players and regular lifters routinely read overweight on BMI while carrying very little fat.
- Age. Over 65, a slightly higher BMI is often protective; aggressive weight loss can cost muscle and bone.
- Pregnancy and children. BMI is not valid in pregnancy, and children need age and sex-specific centile charts.
Frequently asked questions
- What is a healthy BMI for Asian and Black adults?
- The NHS advises adults of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background to aim for a BMI between 18.5 and 23. Above 23 counts as overweight and 27.5 or more counts as obesity, because the risk of type 2 diabetes and heart disease rises at a lower body weight in these groups.
- Why is the BMI threshold 23 instead of 25?
- At the same BMI, people of South Asian and Black African heritage tend to carry more visceral fat around the organs and have less muscle mass than white Europeans. Population studies found the same diabetes and cardiovascular risk appears roughly two BMI points earlier, so health bodies lowered the overweight cut-off to 23 and the obesity cut-off to 27.5.
- How is BMI calculated?
- BMI is your weight in kilograms divided by your height in metres squared. A 70 kg adult who is 1.70 m tall has a BMI of 70 / (1.70 x 1.70) = 24.2. In imperial units it is weight in pounds divided by height in inches squared, multiplied by 703.
- Is BMI accurate for everyone?
- No. BMI does not distinguish muscle from fat, so athletes and very muscular people can read as overweight. It is also less reliable in pregnancy, for people over 65 and for children, who need age and sex-specific growth charts. Waist measurement is a useful companion check: aim for less than half your height.
- What waist size goes with a healthy BMI?
- Keep your waist under half your height. As a guide, health services suggest under 94 cm (37in) for men and under 80 cm (31.5in) for women, and under 90 cm (35in) for South Asian men, because central fat is the strongest single predictor of type 2 diabetes.
This calculator is for general information and is not medical advice. If you are worried about your weight, your blood sugar or your heart health, speak to a GP or a registered dietitian.