Importance of BMI

Overweight and obesity have dramatically increased across all age groups, including preschool aged children.

In 2003, the Australian National Health and Medical Research Council (NHMRC) released guidelines on children’s BMI. These make it possible to classify healthy weight and overweight in children from the age of two upwards.

Why weight is important

Having a healthy body weight is important to all people, especially children, to optimise their health outcomes. Overweight and obesity are associated with greater health risks, even in young children.

Low weight is occasionally an indicator for poor health or sickness. However, most “thin” children are healthy. In general, being overweight/obese poses a greater threat to long-term health than being “underweight”. Being a healthy weight helps children have a better self-esteem and confidence, improves participation in sport and active play and improves sleep.

Health professionals can play an important role in helping to promote a healthy weight in children.

Health and social risks

Overweight and obesity strictly mean having an excess of adipose tissue (body fat). We need a certain amount of body fat for normal, healthy functioning of the body. However, an excess of body fat is detrimental to our health.

Childhood overweight and obesity can have immediate effects, though most young overweight children seem healthy. Traditionally it was thought that young overweight children would “grow out of it” or that it was just “puppy fat”, but this is not now generally the case. Unless weight is managed effectively, we know that most overweight children become overweight adults, and this can result in long term health problems.

The following table summarises some of the short and long term health and social risks that have been found to result from overweight and obesity.

Short and long term health and social risks

Obesity problems during childhood


  • high blood fat levels
  • increased blood pressure
  • insulin resistance
  • impaired glucose tolerance.

Social factors

  • decresaed self esteem
  • decreased quality of life
  • social marginilisation.
Long term health risks if childhood overweight and obesity persists through to adulthood

Increased risk of

  • diabetes
  • coronary heart disease
  • stroke
  • osteoarthritis
  • high blood pressure
  • non-alcoholic fatty liver disease
  • some cancers (e.g. breast, colon, prostate)
  • infertility
  • social and employment problems.

Terminology for overweight

A wide variety of terms and phrases are used to describe overweight.

Internationally there tends always to be two categories describing overweight status. The most widely accepted and recognised clinical terms are “overweight” and “obese”.

The term “overweight” is self explanatory, whilst the term “obese” is used when someone is very overweight. There are clear criteria to determine whether an individual is overweight or obese and these terms should only be used after applying these criteria.

In Australia and many other countries worldwide “overweight” and “obese” are the accepted clinical classifications for children. In the USA, overweight children are classified as “at risk of overweight” and obese children as “overweight.”

The International Obesity Task Force (IOTF) has developed a new approach to defining childhood overweight and obesity to make it consistent with the adult definition (Cole et al, BMJ 2000). However, it takes time for these definitions to become fully integrated worldwide.

As well as clinical terms, numerous colloquial terms describe overweight. Some of these are more acceptable than others. For clinical and colloquial terms that parents may find more or less acceptable, see Initiating Discussion.

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