Why use BMI?īMI is an easy and non-invasive method of accurately and consistently assessing excess body fat at a population level. True measures of BMI are expensive or impractical and other proxy measures are more difficult to measure precisely.īMI data has been compiled worldwide to give an overview of people’s health and weight across various populations. However, if a person has a very low BMI, this could indicate they have too little body fat, which can lead to other health problems such as anaemia, lowered immunity, and decreased bone density.Īs BMI is a screening tool only - doctors would need to carry out further tests, such as a skinfold thickness check, waist measurements, diet and physical activity evaluations, and family history to accurately assess an individual’s overall health as BMI cannot alone be used as a diagnostic tool.Ī BMI check is, therefore, most commonly used for monitoring the prevalence of overweight and obesity at a population level rather than an individual level. For example, a person with a high BMI indicates they may have high body fat levels, which could lead to an increased risk of developing obesity-related illnesses, such as heart disease and type II diabetes. How is BMI used?īMI is a proxy measure of excess body fat.ĭoctors use the Body Mass Index as a screening tool to identify a person’s weight category. The link between BMI thresholds and future morbidity and mortality is weaker for children than adults, but evidence shows that children with a high BMI are more likely to have a high BMI in adulthood and, therefore, a raised risk of future health problems. For example, a healthy weight for a typical child would be between the 3rd and 91st percentile. The result is given as a percentile ranking. Obesity = BMI of 30 or above How does BMI work for children?įor children, although BMI is still calculated the same as for adults, it also considers the age and gender of the child, as other factors, such as the timing of puberty, can make the classification of a child’s BMI more complex.Ī child’s average BMI measurements are compared to a growth reference (usually the UK90 Growth Reference) to more accurately determine if a child’s weight is right for their height. The Body Mass Index indicates an ideal BMI for most adults. You just need to divide a person's weight by the square of their height to calculate their average BMI.īMI = Weight (kg) / Height (m)² BMI Range How does BMI formula work for adults?Ī standard BMI formula ( or height weight calculator) is used to calculate an adult's BMI. It has now become the standard formula for assessing a person's risk of developing weight-related diseases, such as heart disease, high blood pressure, and diabetes. In 1985 the National Institutes of Health (NIH) recommended that physicians adopt the BMI as an index of obesity.

Based on this measurement, a person’s weight will be categorised as either underweight, within the healthy BMI range, overweight, or obese, as defined by the World Health Organization (WHO). The definition of body mass index (BMI) is the measurement of a person’s weight in relation to their height.

Metric bmi calculator children