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What Are You Made Of?

IAEA Works to Standardise Body Composition Assessment

To evaluate how well different types of food sustain growth, nutrition scientists use stable isotopes of elements such as hydrogen and oxygen and nuclear analytical techniques to assess body composition. (Photo: L. Davidsson/IAEA)

In the science of body composition, the underlying premise is that - where you begin, or rather how you begin, determines how you´ll end up. Essentially, growth patterns in early childhood affect health in later life.

Research shows that a child´s weight at birth is an indicator of the probability of that child developing chronic diseases like diabetes and hypertension in middle age.

"Most nutrition scientists agree that if you want to provide children with a better possibility to survive and grow into healthy, productive adults, you need to intervene when they are between 0 and 2 years old," says Lena Davidsson, Head of the IAEA´s Nutritional and Health-related Environmental Studies Section.

To determine if a child is at risk, doctors and nurses need to know the proportion of the baby´s fat to muscle mass, and whether it is appropriate for the child´s age. Also, they need to know how quickly the baby is putting on weight, which is an indicator of future health risk.

A number of methods are used to assess body composition, and nuclear techniques are the best available to determine the muscle, bone, fat and water content of the body.

"We´re trying to establish what is a standard for normal growth and what is the allowable variation within that," explains Kenneth Ellis, from the Children´s Nutrition Research Center at Baylor College of Medicine in the USA.

"And if we can set these standards and someone starts to deviate from those ranges or going on a path where it looks like they´re going outside these ranges, health workers can then choose a nutritional intervention to set the child back on the right track."

Based on data collected in several countries, the World Health Organisation (WHO) recently created a document that describes how children grow "normally" in various countries, as a guide to health workers. This document - presented in chart form for easy use - is based on body weight, length and height.

The next step is integrating data on body composition into these charts and introducing body composition assessment into the standard package of health care in clinics around the world. The IAEA, along with the WHO and other organisations involved in nutrition studies, is working to achieve that.

"It´s difficult to measure body composition in very young infants," says Davidsson. "There are a number of methods that are used, and some are being used inappropriately; so we need to make sure there is standardisation, that across the world everyone knows how to get the most accurate results."

"The IAEA has a long history of providing guidance on the use of methodologies, and that´s why the Agency is taking the lead on this issue," she says.

In 2010 the IAEA will produce a document on body composition assessment standardisation in children from 0-5 years. A group of nutrition experts from around the world, including the WHO, gathered at the IAEA headquarters last month to discuss the critical areas that the publication would cover.


Nuclear techniques help researchers by increasing the sensitivity and specificity of body composition measurements.

All assessment methods, whether by measuring potassium or body water, aim to determine the proportion of muscle mass and fat. Nuclear techniques for body composition assessment include stable isotope technique and dual energy x-ray absorptiometry (DXA).

Other non-nuclear techniques like bioelectrical impedance (BIA) need to be used in conjunction with nuclear techniques like total body water (TBW).

Last update: 27 July 2017