The study, published in the online edition of Nutrition Journal, support current dietary guidelines, suggesting that children should have a certain amount of fat in their diet, to meet their energy and nutritional needs.
Led by John Kostyak, a team of researchers used calorimetry to measure whole body fat oxidation in 10 children (aged 6-10) and 10 adults. All had a body mass index (BMI) within the healthy, middle range.
The researchers checked subjects' cardiovascular fitness and body fat, and gave them the same typical American diet for three days prior to testing, although adults had larger portions. The subjects spent nine hours on three separate days at a low physical activity level, watching movies or reading, in either a room calorimeter or under a hood system, which quantify oxygen and carbon dioxide gas levels.
The authors also measured the total amount of nitrogen in the subjects' urine, and used these measurements to calculate how much fat they oxidised.
Although the absolute amount of fat burned in a day did not differ greatly between children and adults, children burned considerably more fat relative to the amount of energy they used. Women and girls used fat at a higher rate than men and boys of a comparable age.
"Prepubescent children may oxidise more fat relative to total energy expenditure than adults for the purpose of supporting normal growth processes such as higher rates of protein synthesis, lipid storage and bone growth. Sufficient fat must be included in the diet for children to support normal growth and development," says Kostyak.