Daily energy expenditure in free-living conditions in obese and non-obese children: Comparison of doubly labelled water (2H218O) method and heart-rate monitoring

OBJECTIVE: To compare the heart-rate monitoring with the doubly labelled water (2H218O) method to estimate total daily energy expenditure in obese and non-obese children. DESIGN: Cross sectional study of obese and normal weight children. SUBJECTS: 13 prepubertal children: six obese (4M, 2F, 9.1 ± 1.5 years, 47.3 ± 9.7 kg) and seven non-obese (3M, 4F, 9.3 ± 0.6 years, 31.8 ± 3.2 kg). MEASUREMENTS: Total daily energy expenditure was assessed by means of the doubly labelled water method TEE(DLW) and of heart-rate monitoring (TEE(HR)). RESULTS: TEE(HR) was significantly (P < 0.05) higher than TEE(DLW) in obese children (9.47 ± 0.84 MJ/d vs 8.99 ± 0.63 MJ/d) whereas it was not different in non-obese children (8.43 ± 2.02 MJ/d vs 8.42 ± 2.30 MJ/d, P = NS). The difference of TEE assessed by HR monitoring in the obese group averaged 6.2 ± 4.7%. At the individual level, the degree of agreement (difference between TEE(HR) and TEE(DLW) ± 2s.d.) was low both in obese (-0.36, 1.32 MJ/d) and in non-obese children (-1.30, 1.34 MJ/d). At the group level, the agreement between the two methods was good in non-obese children (95% c.i, for the bias:-0.59, 0.63 MJ/d) but not in obese children (0.04, 0.92 MJ/d). Duration of sleep and energy expenditure during resting and physical activity were not significantly different in the two groups. Patterns of heart-rate (or derived energy expenditure) during the day-time were similar in obese and non-obese children. CONCLUSION: The HR monitoring technique provides an estimation of TEE close to that assessed by the DLW method in non-obese prepubertal children. In comparison with DLW, the HR monitoring method yields a greater TEE value in obese children.