Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults.BMI is calculated as the weight (in kilograms) divided by the square of the height (in metres) or BMI = Kg/M2.
BMI does not measure body fat directly, but research has shown that BMI is moderately correlated with more direct measures of body fat obtained from skinfold thickness measurements, bioelectrical impedance, densitometry (underwater weighing), dual energy x-ray absorptiometry (DXA) and other methods. BMI appears to be as strongly correlated with various metabolic and disease outcome as are these more direct measures of body fatness. In general, BMI is an inexpensive and easy-to-perform method of screening for weight category, for example underweight, normal or healthy weight, overweight, and obesity.
A high BMI can be an indicator of high body fatness. BMI can be used as a screening tool yet it is not a diagnostic tool of the body fatness or health of an individual.To determine if a high BMI is a health risk, a healthcare provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings.
BMI is interpreted differently for children and teens, even though it is calculated using the same formula as adult BMI. Children and teen’s BMI need to be age and sex-specific because the amount of body fat changes with age and the amount of body fat differs between girls and boys. Consultation of a Pediatrician or a Pediatric Endocrinologist is suggested.
The International Classification of adult underweight, overweight and obesity according to BMI
|Principal cut-off points||Additional cut-off points|
|Moderate thinness||16.00 – 16.99||16.00 – 16.99|
|Mild thinness||17.00 – 18.49||17.00 – 18.49|
|Normal range||18.50 – 24.99||18.50 – 24.99|
|Pre-obese||25.00 – 29.99||25.00 – 29.99|
|Obese class I||30.00 – 34.99||30.00 – 34.99|
|Obese class II||35.00 – 39.99||35.00 – 39.99|