What is overweight and obesity?
Overweight and obesity are defined as ''abnormal or excessive fat accumulation that presents a risk to health''.
Measuring overweight and obesity
It is difficult to develop one simple index for the measurement of overweight and obesity in children and adolescents because their bodies undergo a number of physiological changes as they grow. Depending on the age, different methods to measure a body's healthy weight are available:
For children aged 0-5 years
The WHO Child Growth Standards, launched in April 2006, include measures for overweight and obesity for infants and young children up to age 5.
For individuals aged 5-19 years
WHO developed the Growth Reference Data for 5-19 years. It is a reconstruction of the 1977 National Center for Health Statistics (NCHS)/WHO reference and uses the original NCHS data set supplemented with data from the WHO child growth standards sample for young children up to age 5.
The most commonly used measure for overweight and obesity is the Body Mass Index (BMI) - a simple index to classify overweight and obesity in adults. It is defined as the weight in kilograms divided by the square of the height in meters (kg/m2).
The BMI provides the most useful population-level measure of overweight and obesity, as it is the same for both sexes and for all ages of adults. However, it should be considered as a rough guide because it may not correspond to the same body fat percentage in different individuals.