Weight Management
How BMI Is Used in Weight Management
What BMI measures, how the UK ranges work, why thresholds differ by ethnicity, and why BMI is only part of the picture.
JoinGRI Editorial Team · · 1 min read
What BMI measures
Body mass index compares weight with height: weight in kilograms divided by height in metres squared. It’s quick and needs no equipment, which is why it’s widely used.
The adult ranges
- Below 18.5: underweight range
- 18.5 to 24.9: healthy weight range
- 25 to 29.9: overweight range
- 30 or above: obesity range
Different thresholds for different groups
People from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds have a higher risk of some conditions at a lower BMI, so UK guidance uses lower thresholds — for example 23 and 27.5.
Beyond BMI
Healthcare professionals often add a waist-to-height ratio: a waist measurement of more than half your height can indicate increased risk. They also consider health conditions, medicines and history.
How BMI is used
BMI helps start a conversation and track change over time. It doesn’t diagnose anything and doesn’t, on its own, decide whether any treatment is suitable. Work out yours with our BMI calculator.
Frequently asked questions
What is a healthy BMI?
For most adults, the NHS describes 18.5 to 24.9 as the healthy weight range. Lower thresholds are used for people from some ethnic backgrounds.
Why might my BMI be misleading?
BMI doesn’t distinguish muscle from fat or show where weight is carried, so it can be misleading for very muscular people, older adults and some others.
Sources and further reading
This article is for general education only. It isn’t medical advice and doesn’t replace a conversation with a qualified healthcare professional about your own circumstances.