The House of Commons Select Committee on obesity, and two expert groups in the USA, recommend that the body mass index (BMI) of every school child should be measured each year and the result sent home to the parents. The BMI correlates sufficiently well with direct measures of total body fat to support its use, on an anonymous basis, as a public health tool for monitoring progress in dealing with the obesity epidemic. However, the BMI is an imperfect proxy for obesity because there is much individual variability in the relationship between BMI and body fat, cardiovascular risk factors, and long term health outcomes. Whatever BMI cut offs are selected for determining the advice to parents, a high BMI calls for further evaluation and interpretation and the policy proposed by the Select Committee, to send BMI results to parents, is therefore in effect a screening programme. As such, it presents a number of difficulties and should be implemented only as a research study and not as public policy.

The worldwide epidemic of childhood obesity is a public health problem for two reasons. First, it is associated with a variety of adverse health outcomes, including type 2 diabetes and cardiovascular disease. Second, it is perceived in the Western world as unattractive and for many individuals it is, therefore, the cause of much unhappiness. The UK Government has set a target of “halting the rise” in childhood obesity by 2010.¹ Concerns about obesity have generated much interest in the body mass index (BMI) as a convenient indicator of body fat and the House of Commons Select Committee on Health² recommended that:

… throughout their time at school, children should have their Body Mass Index measured …