Obesity in Children

Childhood obesity is an important health issue today. Over the past 10 years it has become the most common childhood metabolic disorder. Sedentary lifestyles and poor diet are undoubtedly part of the problem, however in some there is also a genetic or endocrine element. Obesity may effect up to 10% of six year olds, and up to 17% at 15 years. In many cases both parents and children are quick to attribute the child's weight to a glandular problem. In reality this is rarely the case.

What measures obesity?

There are many ways to assess body composition. These include anthropometrical measurements such as skin fold thickness and MRI, which is the most accurate method. In the clinical setting Body Mass Index (BMI) is the method most commonly used. It is calculated by dividing a person's weight in kilograms by the square of their height in metres.

BMI = Weight (Kg)

Height (m2)


BMI is a crude measurement of obesity, as it fails to take into account lean mass. However it only requires simple measurements of weight and height and it is reproducible.

The International Obesity Task Force guidelines for adult measurements say that a BMI greater then 25kg/m2 is overweight, while a BMI greater then 30 kg/m2 is clinically obese. As children's bodies are composed differently to that of adults there are specific centile charts on which a child's age and BMI may be mapped to determine whether their weight is appropriate for their age.

Childrens Body Mass Index graph

Childrens BMI graph - click to enlarge

There is no data at present to correlate BMI with illness during childhood, so the cut off points above are used as a predictor of morbid obesity of adulthood.