What are obesity and overweightOverweight and obesity are defined as abnormal or excessive fat accumulation that may impair health.
Body mass index (BMI) is a simple index of weight-for-height that is commonly used to classify overweight and obesity in adults. It is defined as a person’s weight in kilograms divided by the square of his height in meters (kg/m2).
Adults
For adults, WHO defines overweight and obesity as follows:
- overweight is a BMI greater than or equal to 25; and
- obesity is a BMI greater than or equal to 30.
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 a rough guide because it may not correspond to the same degree of fatness in different individuals.
For children, age needs to be considered when defining overweight and obesity.
Children under 5 years of age
For children under 5 years of age:
- overweight is weight-for-height greater than 2 standard deviations above WHO Child Growth Standards median; and
- obesity is weight-for-height greater than 3 standard deviations above the WHO Child Growth Standards median.
