Assessment of energy expenditure in metabolic disorders.

The assessment of energy expenditure is valuable for the management of children with various conditions such as obesity and failure to thrive. Total daily energy expenditure (TDEE) includes resting energy expenditure (REE), energy expenditure during physical activity, dietary thermogenesis and growth. TDEE can be assessed by using the double-labelled water technique, but it has complex pitfalls and potential sources of errors and is impractical for everyday use. As REE is a substantial part of TDEE (65%-70%) and computerised indirect calorimeters have become recently available, this non-invasive, relatively cheap and easy to use technique is valuable for the assessment of short-term changes in energy metabolism. This can be used to assess REE of children with inborn errors of metabolism, whilst well and during episodes of metabolic decompensation and therefore to accurately determine energy intake.