BMI and the NHS categories
The NHS uses BMI as a general guide: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30+ obese. It’s a screening tool and doesn’t account for muscle mass or ethnicity-specific thresholds.
Lower thresholds for some ethnic groups
The NHS advises that people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds face weight-related health risks at a lower BMI. For these groups the overweight band can start at 23 and the higher-risk band at 27.5, rather than 25 and 30 — worth bearing in mind when reading your result.
Why waist size matters too
Where you carry weight affects risk as much as how much. The NHS suggests keeping your waist under half your height as a simple check. A large waist with a “healthy” BMI can still signal raised risk, while a stocky, muscular build can read as overweight without excess fat — so use BMI alongside, not instead of, other measures.