Childhood obesitySignificant developments have been made in the fight against obesity, with the publication of research highlighting that children of a similar age and gender can have widely varied levels of muscle mass – a relationship that is masked by BMI (Paediatric Obesity Journal, Volume 9: Issue 4) These findings pose a challenge to the existing methods of assessing obesity amongst children and young adults.

This groundbreaking research commissioned by the global leader in health monitoring Tanita, was carried out by leading scientists (*1) on 3,000 children aged between 5 and 18 years using the Tanita Body Composition Analyzer, which uses segmental BIA (Bioelectrical Impedance Analysis) to measure the relationship between fat and muscle. It is this relationship which provides a more meaningful interpretation of a child’s body composition.

As a result of this research new sex-specific muscle mass reference curves for children using BIA technology are now available for researchers and clinicians and healthcare practitioners to use alongside the existing BMI and waist circumference centiles, to give a clear insight into the make- up of the individual and their potential health risks in later life.

Muscle mass is being increasingly recognised as an independent marker of a child’s health status. Low muscle fitness is associated with metabolic risk and muscular strength is associated with higher insulin sensitivity in children and adolescents.

However, the absence of appropriate measurement tools has limited the expansion and application of such knowledge.  Segmental BIA now offers a route to overcoming these limitations by providing an affordable, robust and non-invasive means for doctors and nurses to monitor appendicular skeletal muscle mass (ASMM) and gain a clearer understanding of the child’s composition.  In turn, this will ensure more precise clinical assessments, with the ability to identify young people who are more likely to be at the risk of ill health over and above BMI, and monitor the effect of obesity treatments where the goal is to maximize fat loss and increase muscle mass. 

‘These curves give us a huge opportunity to focus upon the relationship between fat and muscle in children in a way that has not been possible before. It could be that the balance between these two tissues holds the key to later risk for metabolic diseases such as type 2 diabetes, hypertension and certain cancers,’ explains one of the authors, Professor David McCarthy from the Institute for Health Research & Policy at London Metropolitan University.

‘Up until now, there has been a major focus on the ill effects of a large fat mass without full consideration of the compensatory value of a large, healthy and exercised muscle mass. We would expect that children with a low muscle mass: fat ratio would be at much greater risk than those a high ratio. Fat and muscle (& lean tissue more generally) have opposing effects on glucose sensitivity and hence the ratio of the two masses is an important determinant of health, especially in relation to insulin resistance and the associated metabolic syndrome,’ comments another author, Professor Andrew Prentice, Head of the MRC International Nutrition Group at The London School of Hygiene and Tropical Medicine .

In 2005, Tanita developed gender-specific Body Fat Reference Curves for boys and girls, which were added to the standard range of UK centile charts of BMI and waist circumference.  Based on a two-year study (*2) these curves highlighted a gender difference which was most evident after puberty, where there was a marked divergence in fatness; girls continue to gain fat but boys gain more muscle and lean tissue.  At the age of 18, the girls have proportionately 60% more fat than the boys, with the average body fat percentages being 24.6% and 15% respectively. 

In the past decade, there has been a great deal of research and initiatives undertaken by the government to reduce obesity and increase physical activity, especially amongst young people. Both studies highlight that whilst BMI (body mass index) is widely used as a simple and valuable tool to assess children’s height/weight ratio, it has serious limitations in assessing normal growth and development which can in turn cause misclassification. Unlike BIA, upon which both studies were based, BMI cannot distinguish between increased weight in the form of fat or lean tissue. BIA is therefore increasingly being seen as the only cost-effective method to accurately monitor the progress of a child health scheme.

Another author Dr Susan Jebb, Professor of Diet & Population Health at Nuffield Department of Primary Care Health Sciences, Oxford University, concludes:

 ‘The commonly-used body mass index (BMI) is a useful guide to assess the prevalence of obesity in populations or within subgroups of the population such as age, gender or social class. But it has limited value for individuals, especially children because of complex relationships between fat and lean tissue during growth and development.  A heavy child may be large-boned, heavily muscled, or overfat. Segmental BIA offers healthcare professionals an extremely useful standard assessment tool in its ability to monitor changes in fat and muscle mass.’

For more information on this research or Tanita Body Composition Analysers please contact or call +44 (0)1245 492986