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Definitions of overweight and obesity

The Body Mass index (BMI) is the common method of evaluating individual people to see if they are under or overweight. It involves comparing their weight to their height by dividing the weight measurement (expressed in kilograms) by the square of the height (expressed in meters).

Source: Adapted from WHO, 1995, WHO, 2000 and WHO 2004

There is on-going debate on the definition of overweight and obesity in childhood. BMI is a measure of overweight and obesity in children although it is liable to change substantially as the child is growing. The clinical definition of overweight and obesity in children is based on BMI percentile charts for boys and girls plotted at different ages from 2-16 years. The National Institute for Health and Clinical Excellence (NICE) recommends that tailored clinical intervention should be considered for children with a BMI at or above the 91st centile, depending on the needs of the individual child and family, and that an assessment of comorbidity should be considered for children with a BMI at or above the 98th centile.

In adults, waist measurements also provide a good obesity indicator. A report by the World Health organisation suggests that increased risk is present when the waist measurement exceeds 94cm (37 inches) for men or 80cm (32 inches) for women.