The formula for calculating body mass index

A healthy weight

BMI is one way to define a healthy weight

Doctors usually rate people as underweight, normal, overweight or obese by their body mass index (BMI). A higher BMI normally means a higher percentage of body fat; however, this varies according to age, ethnic group and sex. There are also differences between, say, a body-builder who eats piles of protein to add muscle mass and a couch potato who weighs the same but lives on snack foods and, hence, has more body fat.

The BMI is not a perfect measure. It applies best to people who are mainly sedentary, have roughly average body composition and are not too short or tall. Some researchers think that waist size and/or waist-to-hip ratio – or combining these with the BMI – are more useful indicators of a healthy weight.

References

About this resource

This resource was first published in ‘Food and Diet’ in June 2011 and reviewed and updated in August 2016.

Topics:
Statistics and maths, Physiology, Health, infection and disease
Issue:
Food and Diet
Education levels:
16–19, Continuing professional development