A critical examination is made of the validity of indirect calorimetry when the nonprotein respiratory quotient is greater than 1. The different published stoichiometries for lipogenesis from glucose are excluded as a source of uncertainty in the interpretation of gaseous exchange measurements. The validity of indirect calorimetry is proved independently by an algebraic approach which, in contrast to previous attempts, makes minimal assumptions about stoichiometries. Although equations relating the respiratory quotient to the heat equivalent of oxygen are found valid, there is uncertainty in using these equations to predict accurately carbohydrate utilization and fat oxidized or synthesized. Reference tables interrelating respiratory data, the heat equivalent of oxygen, and net fuel utilization or synthesis for specified fuels are provided. A suggested framework for calculating energy expenditure in terms of ATP gain is given as an appendix.

Racial differences in REE were reduced by >50% and were no longer significant when the mass of specific high-metabolic-rate organs was considered. Differences in FFM composition may be responsible for the reported REE differences.

Background: There are few data on the optimal micronutrient composition of paediatric enteral feeds. The recent European Directive on Foods for Special Medical Purposes (1999/21/EC) did not distinguish between the composition of adult and paediatric feeds. Aims: To evaluate, in an open, observational study, the long term nutritional biochemistry of 12 children aged 1-6 years and/or 8-20 kg. Methods: The children were receiving at least 50% of their estimated average requirement (EAR) for energy from paediatric enteral formulae: 1.0 kcal/ml (Nutrison Paediatric Standard) or 1.5 kcal/ml (Nutrison Paediatric Energy Plus). Venous blood samples for trace elements, vitamins, and minerals were taken at study entry and six months later. Parents kept three day food and feed records every month. Results: Despite a median energy intake of only 75% EAR (range 52-158%), 67% (n = 8) achieved their reference nutrient intake (RNI) for all micronutrients. No significant micronutrient deficiencies were seen on blood analysis after six months. Eighty three per cent (n = 10) had vitamin B 12 and 92% (n = 11) had copper intake >150% RNI. Fifty eight per cent (n = 7) had high plasma B 12 (>733 µmol/l) and 75% (n = 9) had high serum copper (>22 µmol/l) concentrations. Conclusions: Children without excess losses maintain adequate micronutrient status on long term enteral feeding. Subjects had high blood concentrations of vitamin B 12 and copper, and had high dietary intakes of these micronutrients. We suggest that the maximum nutrient guidelines for paediatric enteral feeds should be more clearly defined.

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Objective: To determine physical activity levels (PAL) in children aged between 10 and 13 y. Design: Cross-sectional study of physical activity levels on school days, with and without physical education (PE) lessons and at weekend. Data were collected using self-reported activity diaries. Setting: The children were recruited from a middle school in Oxford. Basal metabolic rate (BMR) and anthropometry were measured in the school. Subjects: Thirty-eight children (12 boys and 26 girls), aged 10 ± 13 y, returned completed activity diaries. PAL values were calculated by applying physical activity ratios (PAR) to the time spent on each activity. BMR and anthropometry were measured within 20 d of activity diary completion. Results: The mean AE s.d. (range) PAL values for all children were 1.52 AE 0.08 (1.34 ± 1.71), 1.50 AE 0.05 (1.44 ± 1.57) for boys and 1.53 AE 0.10 (1.34 ± 1.71) for girls. The lowest PAL value (1.48 AE 0.13, mean AE s.d.) was observed in girls on school days without PE lessons. The lowest PAL value in boys (1.46 AE 0.13, mean AE s.d.) was observed at the weekend. PE lessons made a signi®cant difference to the PAL values for boys (1.58 AE 0.09) and girls (1.60 AE 0.12). A wide range of PAL values (1.20 ± 1.87) was recorded in these children. The total energy expenditure for the boys was slightly lower than the estimated average requirements (EAR) predicted by the Department of Health (8.71 AE 0.96 MJ compared with 8.86 MJad) for this age group. The girls had a higher average energy expenditure than the predicted EAR (8.47 AE 1.00 MJad compared with 7.885). Conclusions:The children in this study may be classi®ed as light to moderately active with PAL values ranging from 1.20 to 1.87. The promotion of physical activity in childhood will have bene®cial effects for the child and their future wellbeing. Programmes aimed at preventing obesity in children should encourage physical activity as well as promoting appropriate dietary changes.