Relative fat oxidation is higher in children than adults

Prepubescent children may oxidize fatty acids more readily than adults. Therefore, dietary fat needs would be higher for children compared with adults. The dietary fat recommendations are higher for children 4 to 18 yrs (i.e., 25 to 35% of energy) compared with adults (i.e., 20 to 35% of energy). Despite this, many parents and children restrict dietary fat for health reasons.

This study assessed whether rates of fat oxidation are similar between prepubescent children and adults. Ten children (8.7 +/- 1.4 yr, 33 +/- 13 kg mean +/- SD) in Tanner stage 1 and 10 adults (41.6 +/- 8 yr, 74 +/- 13 kg) were fed a weight maintenance diet for three days to maintain body weight and to establish a consistent background for metabolic rate measurements (all foods provided). Metabolic rate was measured on three separate occasions before and immediately after breakfast and for 9 hrs using a hood system (twice) or a room calorimeter (once) where continuous metabolic measurements were taken.

During all three sessions whole body fat oxidation was higher in children (lower RQ) compared to adults (mean RQ= 0.84 +/- .016 for children and 0.87 +/- .02, for adults, p < 0.02). Although, total grams of fat oxidized was similar in children (62.7 +/- 20 g/24 hrs) compared to adults (51.4 +/- 19 g/24 hrs), the grams of fat oxidized relative to calorie expenditure was higher in children (0.047 +/- .01 g/kcal, compared to adults (0.032 +/- .01 p < 0.02). Females oxidized more fat relative to calorie expenditure than males of a similar age. A two way ANOVA showed no interaction between gender and age in terms of fat oxidation.

These data suggest that fat oxidation relative to total calorie expenditure is higher in prepubescent children than in adults. Consistent with current dietary guidelines, a moderate fat diet is appropriate for children within the context of a diet that meets their energy and nutrient needs.