PII: S0022-3476(95)70387-X

Abstract

Reply To the EditorSchoeller and Luke emphasize that our article should be interpreted with caution because resting energy expenditure (REE) was measured under conditions that were less than optimal. In our experience with hundreds of measurements, the key to obtaining reliable measures of REE in children is to minimize stress. We therefore allowed the children to watch videotaped cartoons and to eat their normal breakfast at home before reporting to the laboratory. This protocol ensures that young children maintain a relaxed and cooperative mood during testing, thus leading to excellent measurement reliability (the test-retest reliability is ~5%).We have completed studies (unpublished observations) in which we compared the postprandial protocol with the more typical “basal” conditions used in adults. Metabolic rate was ~11% higher when measured under postprandial conditions. This finding is consistent with measurements of postprandial REE by Maffeis et al.,1Maffeis C Schutz Y Zoccante L Micciolo R Pinelli L. Meal-induced thermogenesis in lean and obese prepubertal children.Am J Clin Nutr. 1993; 57: 481-485PubMed Google Scholar suggesting that the elevation in metabolic rate with the postprandial protocol is explained by the additional energy cost of meal consumption. In addition, we found that the correlation between REE and fat-free mass was stronger when measurements were performed under postprandial (r = 0.88) versus “basal” conditions (r = 0.64), but the regression slope was similar. These findings suggest that the postprandial protocol reduces measurement noise without compromising the nature of the relationship between REE and fat-free mass.We believe that allowing children to watch television is another factor that contributes to more reliable and less “fidgety” measurement of REE. This is supported by data from two other laboratories. Dietz et al.2Dietz WH Bandini LG Morelli JA Peers KF Ching PLYH. Effect of sedentary activities on resting metabolic rate.Am J Clin Nutr. 1994; 59: 556-559PubMed Google Scholar showed that children move less when they watch television, in comparison with asking them to sit still, and Klesges et al.3Klesges RC Shelton ML Klesges LM. The effects of television on metabolic rate: potential implications for childhood obesity.Pediatrics. 1993; 91: 281-286PubMed Google Scholar showed that energy expenditure was reduced during television viewing in obese and nonobese girls.A final advantage of the postprandial protocol is that the measurements are performed under conditions that are physiologically representative (a 12-hour fasted state is not natural for a young child). Schoeller and Luke challenge this idea because we published data in which REE exceeded total energy expenditure in several children.4Goran MI Carpenter WH Poehlman ET Total energy expenditure in 4 to 6 year old children.Am J Physiol. 1993; 264: E706-E711PubMed Google Scholar In 100 studies we have noted a higher REE in four cases (by 20 to 50 kcal/day). Our interpretation of REE being higher than total energy expenditure is that the relevant techniques are subject to measurement error.Although we do not advocate the use of the alternative protocol in all situations, it does offer several advantages: (1) it is reproducible, (2) children may move less during measurement, (3) it is practical and can be applied to large numbers of children or in a clinical setting, and (4) the measurement is performed under conditions that would be encountered during the course of a typical day. As pointed out by Schoeller and Luke, the limitations to such a protocol are that metabolic rate cannot be resolved into its basal and postprandial components and that it may be difficult to compare data with other studies.9/35/62655 Reply To the EditorSchoeller and Luke emphasize that our article should be interpreted with caution because resting energy expenditure (REE) was measured under conditions that were less than optimal. In our experience with hundreds of measurements, the key to obtaining reliable measures of REE in children is to minimize stress. We therefore allowed the children to watch videotaped cartoons and to eat their normal breakfast at home before reporting to the laboratory. This protocol ensures that young children maintain a relaxed and cooperative mood during testing, thus leading to excellent measurement reliability (the test-retest reliability is ~5%).We have completed studies (unpublished observations) in which we compared the postprandial protocol with the more typical “basal” conditions used in adults. Metabolic rate was ~11% higher when measured under postprandial conditions. This finding is consistent with measurements of postprandial REE by Maffeis et al.,1Maffeis C Schutz Y Zoccante L Micciolo R Pinelli L. Meal-induced thermogenesis in lean and obese prepubertal children.Am J Clin Nutr. 1993; 57: 481-485PubMed Google Scholar suggesting that the elevation in metabolic rate with the postprandial protocol is explained by the additional energy cost of meal consumption. In addition, we found that the correlation between REE and fat-free mass was stronger when measurements were performed under postprandial (r = 0.88) versus “basal” conditions (r = 0.64), but the regression slope was similar. These findings suggest that the postprandial protocol reduces measurement noise without compromising the nature of the relationship between REE and fat-free mass.We believe that allowing children to watch television is another factor that contributes to more reliable and less “fidgety” measurement of REE. This is supported by data from two other laboratories. Dietz et al.2Dietz WH Bandini LG Morelli JA Peers KF Ching PLYH. Effect of sedentary activities on resting metabolic rate.Am J Clin Nutr. 1994; 59: 556-559PubMed Google Scholar showed that children move less when they watch television, in comparison with asking them to sit still, and Klesges et al.3Klesges RC Shelton ML Klesges LM. The effects of television on metabolic rate: potential implications for childhood obesity.Pediatrics. 1993; 91: 281-286PubMed Google Scholar showed that energy expenditure was reduced during television viewing in obese and nonobese girls.A final advantage of the postprandial protocol is that the measurements are performed under conditions that are physiologically representative (a 12-hour fasted state is not natural for a young child). Schoeller and Luke challenge this idea because we published data in which REE exceeded total energy expenditure in several children.4Goran MI Carpenter WH Poehlman ET Total energy expenditure in 4 to 6 year old children.Am J Physiol. 1993; 264: E706-E711PubMed Google Scholar In 100 studies we have noted a higher REE in four cases (by 20 to 50 kcal/day). Our interpretation of REE being higher than total energy expenditure is that the relevant techniques are subject to measurement error.Although we do not advocate the use of the alternative protocol in all situations, it does offer several advantages: (1) it is reproducible, (2) children may move less during measurement, (3) it is practical and can be applied to large numbers of children or in a clinical setting, and (4) the measurement is performed under conditions that would be encountered during the course of a typical day. As pointed out by Schoeller and Luke, the limitations to such a protocol are that metabolic rate cannot be resolved into its basal and postprandial components and that it may be difficult to compare data with other studies. Schoeller and Luke emphasize that our article should be interpreted with caution because resting energy expenditure (REE) was measured under conditions that were less than optimal. In our experience with hundreds of measurements, the key to obtaining reliable measures of REE in children is to minimize stress. We therefore allowed the children to watch videotaped cartoons and to eat their normal breakfast at home before reporting to the laboratory. This protocol ensures that young children maintain a relaxed and cooperative mood during testing, thus leading to excellent measurement reliability (the test-retest reliability is ~5%). We have completed studies (unpublished observations) in which we compared the postprandial protocol with the more typical “basal” conditions used in adults. Metabolic rate was ~11% higher when measured under postprandial conditions. This finding is consistent with measurements of postprandial REE by Maffeis et al.,1Maffeis C Schutz Y Zoccante L Micciolo R Pinelli L. Meal-induced thermogenesis in lean and obese prepubertal children.Am J Clin Nutr. 1993; 57: 481-485PubMed Google Scholar suggesting that the elevation in metabolic rate with the postprandial protocol is explained by the additional energy cost of meal consumption. In addition, we found that the correlation between REE and fat-free mass was stronger when measurements were performed under postprandial (r = 0.88) versus “basal” conditions (r = 0.64), but the regression slope was similar. These findings suggest that the postprandial protocol reduces measurement noise without compromising the nature of the relationship between REE and fat-free mass. We believe that allowing children to watch television is another factor that contributes to more reliable and less “fidgety” measurement of REE. This is supported by data from two other laboratories. Dietz et al.2Dietz WH Bandini LG Morelli JA Peers KF Ching PLYH. Effect of sedentary activities on resting metabolic rate.Am J Clin Nutr. 1994; 59: 556-559PubMed Google Scholar showed that children move less when they watch television, in comparison with asking them to sit still, and Klesges et al.3Klesges RC Shelton ML Klesges LM. The effects of television on metabolic rate: potential implications for childhood obesity.Pediatrics. 1993; 91: 281-286PubMed Google Scholar showed that energy expenditure was reduced during television viewing in obese and nonobese girls. A final advantage of the postprandial protocol is that the measurements are performed under conditions that are physiologically representative (a 12-hour fasted state is not natural for a young child). Schoeller and Luke challenge this idea because we published data in which REE exceeded total energy expenditure in several children.4Goran MI Carpenter WH Poehlman ET Total energy expenditure in 4 to 6 year old children.Am J Physiol. 1993; 264: E706-E711PubMed Google Scholar In 100 studies we have noted a higher REE in four cases (by 20 to 50 kcal/day). Our interpretation of REE being higher than total energy expenditure is that the relevant techniques are subject to measurement error. Although we do not advocate the use of the alternative protocol in all situations, it does offer several advantages: (1) it is reproducible, (2) children may move less during measurement, (3) it is practical and can be applied to large numbers of children or in a clinical setting, and (4) the measurement is performed under conditions that would be encountered during the course of a typical day. As pointed out by Schoeller and Luke, the limitations to such a protocol are that metabolic rate cannot be resolved into its basal and postprandial components and that it may be difficult to compare data with other studies. 9/35/62655