Is body mass index an appropriate proxy for body fat in children?

As the global prevalence of childhood overweight and obesity spreads to low and middle income countries, there is an increasing need for researchers to assess overweight and obesity in populations where child undernutrition still prevails. Although BMI (body mass index) cutoffs are widely used in research and project evaluations, they have only recently been included in WHO definitions for overweight and obesity in children. This review describes the history of how and why BMI was introduced as a proxy for adiposity in children, the scientific evidence and examples from epidemiological studies. Overall, BMI continues to be a valuable measure in children if the underlying assumptions of the criteria and cut-off values are considered. However, where BMI is associated with height, in children, we recommend using weight for height z-scores.

► In 1832 Quetelet introduced weight/stature3 as a body mass index for adults. ► In 1921, Rohrer introduced weight/stature3 to account for the dimensions of infants. ► Height has been found to be associated with height in some populations of children. ► There are known population differences in height, maturation and body composition. ► Current cutoffs for BMI may overstate obesity and overweight relative tounderweight.