Body mass index (BMI) is an estimate of body composition that correlates an individual’s weight and height to lean body mass. The BMI is thus an index of weight adjusted for stature. An individual’s age, gender, ethnicity, and level of fitness must be considered when using BMI to determine health risk.

Research with children indicates annual increases in BMI are usually due to increases in lean mass rather than fat tissue. Not until late adolescence does fat mass begin to affect the BMI—and adult values begin to be achieved.

Condition                                                          men           women
Protein-calorie malnutrition                                  < 17         < 17

Underweight                                                     < 20          < 19

Acceptable weight                                        20.7 – 27.8    19.1 – 27.3

Intervention indicated                                         > 26.4        > 25.8

Obese                                                             > 27.8       > 27.3

Severely obese                                                 > 31.1          > 32.2

Morbidly obese                                                  > 45.4         > 44

 

Normal BMI Values for Infants and Children

Infants (at birth)                    13

1 year                                  18

6 years                                 15