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J C Wells

Publications and source records attributed to J C Wells.

At least 37 records · Page 2Linked to original sources
PubMed1999

Can body size predict infant energy requirements?

Traditionally, infant energy requirements have been predicted from body size or age, whereas in older children and adults, physical activity is also taken into account. However, the extent to which body size determines energy use in individual infants has not been considered. Data on 232 measurements of total energy expenditure obtained in 124 infants aged 1.5 to 12 months were used to assess the relation between body size and energy use in individuals. Age, weight, and fat free mass consistently predicted total energy expenditure with an error of 21-23%. This contrasts greatly with the error of 10% with which infant basal metabolism can be predicted from anthropometry. Body size is a poor index of the total energy requirements of individual infants, and predictive equations generated from data on healthy infants will be inappropriate for disease states where physical activity or growth is altered.

Aging↗
PubMed1999

Body composition of preterm infants during infancy.

AIMS: To examine body composition in preterm infants. METHODS: Body composition was measured by dual energy x-ray absorptiometry (DEXA) at hospital discharge, term, 12 weeks, and at 6 and 12 months corrected age in 125 infants (birthweight < or = 1750 g, gestational age < or = 34 weeks). RESULTS: Body weight derived by DEXA accurately predicted that determined by conventional scales. In both sexes lean mass (LM), fat mass (FM), %FM, bone area (BA), bone mineral mass (BMM), and bone mineral density (BMD) increased rapidly during the study; significant changes were detectable between discharge and term. At 12 months, LM, BA, and BMM, but not FM, %FM, or BMD were greater in boys than in girls. Corrected for age, LM was less than those of the reference term infant; FM and %FM were similar; BMM was greater. Corrected for weight, LM was similar to those of the reference infant, while the FM and %FM of study infants were slightly greater. CONCLUSIONS: DEXA accurately measures body mass. Body composition in preterm boys and girls differs. Interpretation of DEXA values may depend on whether age or body weight are regarded as the appropriate reference.

Absorptiometry, Photon↗
PubMed1999

Feeding preterm infants after hospital discharge: effect of diet on body composition.

Our purpose in this study was to examine whole body composition, using dual energy x-ray absorptiometry (DEXA) during dietary intervention in preterm infants (< or = 1750 g birthweight, < or = 34 wk gestation). At discharge, infants were randomized to be fed either a preterm infant formula (discharge-6 mo; group A) or a term formula (discharge-6 mo; group B), or the preterm formula (discharge-term) and the term formula (term-6 mo; group C). Nutrient intake was measured between each clinic visit. To measure body composition, DEXA was used at discharge, term, 12 wk, 6 mo, and 12 mo corrected age. The data were analyzed by ANOVA. At discharge, no differences were noted in patient characteristics between groups A, B, and C. Although energy intakes were similar, protein and mineral intakes differed between groups (A > C > B; p < 0.0001). During the study, weight gain and LM gain were greater in group A than B. At 12 mo, weight, LM, FM, and BMM but not % FM or BMD were greater in group A than B. However, the effects of diet were confined to boys, with no lasting effects seen in girls. In summary, therefore, DEXA was precise enough to detect differences in whole body composition during dietary intervention. Increased weight gain primarily reflected an increase in LM and is consistent with the idea that the preterm formula more closely met protein and/or protein-energy needs in rapidly growing preterm male infants.

Absorptiometry, Photon↗
PubMed1998

Energy metabolism in infants and children.

Energy is used continuously in the body and is fundamental to physiologic processes. Requirements of individuals vary in relation to a wide variety of factors, making energy metabolism an issue of great importance to the pediatrician. Techniques are available for short- and long-term measurements of energy expenditure, which serve different purposes. The principal techniques are suitable for the age range from birth to adolescence. The theory of energy metabolism is briefly discussed, including a summary of the different working definitions. The principles and practicalities of classical indirect calorimetry, the doubly labeled water method, the bicarbonate method, and heart rate monitoring are then described.

Bicarbonates↗
PubMed1998

Precision and accuracy in a metabolic monitor for indirect calorimetry.

OBJECTIVE: To determine within-machine and between-machine precision (reproducibility) and accuracy, of the Deltatrac Mk 1 Metabolic Monitor. DESIGN: Within-machine and between-machine comparison for gas exchange (VO2 and VCO2), respiratory quotient (RQ) and energy expenditure (EE). SUBJECTS: 3 Deltatrac Mk 1 Metabolic Monitors. METHODS: Within-machine and between-machine reproducibility were assessed by five successive 10 min gas infusion tests in each machine. Accuracy was assessed by measuring independently the gas content of the infusion mixture. The Deltatrac flowmeters were evaluated by further infusion tests. RESULTS: Within-study reproducibility was < 1 ml/min for VCO2, < 2.5 ml/min for VO2, < 5 kcal/d for EE and < 0.01 for RQ. Between-study reproducibility was < 0.2% for RQ, < 1% for VCO2 and < 2% for VO2 and EE. Between-machine reproducibility was < 0.1% for RQ and < 1% for VO2, VCO2 and EE. Accuracy in all three machines was within 3% for VO2, VCO2 and EE, and within 0.2% for RQ. CONCLUSIONS: The Deltatrac Mk 1 is a very precise metabolic monitor, and is accurate within 3% for gas exchange and EE. RQ is measured with greatest reproducibility and accuracy (within 0.2%), making the monitor particularly suitable for studies of substrate utilisation.

Adult↗
PubMed1998

Energy intake in early infancy and childhood fatness.

OBJECTIVE: To investigate whether aspects of infant energy intake are related to fatness in early childhood. DESIGN: Longitudinal investigation of infants studied at 12 weeks and 2-3.5 y. SUBJECTS: 20 healthy infants, breast-fed or formula-fed, from the general population. MEASUREMENTS: Milk volume intake (MVI) by deuterium turnover, estimated energy intake, weaning status and body composition in infancy, body composition in childhood. RESULTS: MVI was not related to infant skinfolds or percentage fat. Weaning was inversely related to MVI (P < 0.04) at 12 weeks, and inversely related to skinfolds (P = 0.055) and fat mass (P = 0.020) in childhood. MVI and total energy intake were not related to childhood fatness. CONCLUSIONS: Early weaning was associated with a moderate reduction in childhood fatness. Two possible mechanisms are discussed. However, early infant energy intake was not an important determinant of later fatness in this population.

Aging↗
PubMed1998

Estimation of the energy cost of physical activity in infancy.

OBJECTIVE: To estimate physical activity energy expenditure (AEE) in groups of free living infants in the first year of life. DESIGN: Mixed longitudinal study of 124 healthy infants, using 232 estimations of AEE made between 1.5 and 12 months. Infants studied at more than one time point were treated as new cross sectional data points. Total energy expenditure and body composition were estimated using doubly labelled water. Sleeping metabolic rate was predicted from weight. RESULTS: AEE increased from 5% of energy intake at 1.5 months to 34% at 12 months. Growth costs declined by 90%, but metabolisable intake by only 20%, over the same period. CONCLUSIONS: Energy is increasingly diverted from growth to activity during infancy. Values for AEE may aid in estimating energy requirements of groups factorially. Further work is required, however, on individual variability in AEE, and on the effects of disease, hospitalisation, surgery, and malnutrition.

Body Composition↗
PubMed1998

Feeding preterm infants after hospital discharge: effect of dietary manipulation on nutrient intake and growth.

The objective of this study was to compare formula intake, the time of weaning, and growth in preterm infants (< or = 1750-g birth weight, < or = 34-wk gestation) fed a standard term or preterm infant formula after initial hospital discharge. Infants were randomized at hospital discharge to be fed a preterm infant formula from discharge to 6 mo corrected age (group A), a term formula from discharge to 6 mo (group B), or the preterm formula (discharge to term) and the term formula (term to 6 mo (group C). Infants were seen biweekly (discharge to term) and monthly (term to 6 mo), when intake was measured and anthropometry and blood sampling were performed. The results were analyzed using ANOVA. Although nutrient intake was similar, at 6 mo girls were lighter (6829 versus 7280 g) and shorter (64.4 versus 66.0 cm) than boys (p < 0.05). Patient characteristics were similar between the treatment groups. Although the volume of intake differed (B > C > A; p < 0.001), energy intake was similar in the groups. Because of differences in formula composition, protein, calcium, and phosphorus intakes differed (B < C < A; p < 0.001). Lower protein intakes were related to lower blood urea nitrogen levels (B < C < A; p < 0.001). At 6 mo, infant boys in B and C were lighter (6933, 6660 < 7949 g), shorter (65.3, 64.9 < 67.1 cm), and had a smaller head circumference (43.7, 43.7 < 44.8 cm; p < 0.05) than infants in group A. Preterm infants were found to increase their volume of intake to compensate for differences in energy density between formulas. After hospital discharge, infant boys fed a preterm formula grew faster than infant girls fed a preterm formula or infant boys fed a term formula.

Blood Urea Nitrogen↗
PubMed1998

Factors affecting the 2H to 18O dilution space ratio in infants.

In the doubly labeled water (DLW) method, for measurement of energy expenditure in humans, calculation of carbon dioxide production rate is influenced by the ratio (R) of the dilution spaces of the tracer isotopes 2H and 18O. Recent publications have recommended use of a fixed value for R, using a mean population value (meanR) rather than individually derived experimental values. However, most of the data considered previously were derived from adults. Infants are characterized by rapid rates of energy deposition and high body water content, either of which could influence isotope kinetics. We have considered whether use of a fixed R value is suitable for DLW studies of infants, and whether the adult (meanR) value is appropriate. Data from 281 DLW measurements in healthy infants aged 6 wk to 12 mo were analyzed. Mean R of all measurements was 1.036 (SD 0.019), very similar to (meanR) values recommended for adults. We found analytical precision could account for almost all between-subject variation at a single time point. However, we also found relationships between R and age and weight gain, indicating that physiology does influence the space ratio. The effect of weight gain on R was negligible, but changes of (meanR) with age, reflecting changes in percentage body water during infancy, were of sufficient magnitude to affect calculation of energy expenditure significantly. Our analysis suggests that use of a fixed ratio at a single time point in infancy is acceptable, but that the appropriate value of (meanR) changes over the first year of life.

Aging↗
PubMed1997

Can risk factors for over-heating explain epidemiological features of sudden infant death syndrome?

Sudden infant death syndrome is characterized by a number of epidemiological features that have defied simple explanation. Overheating is believed to play a role in its causation. Overheating can be caused by changes in heat production, changes in insulation of the infant, or changes in the external environmental temperature. Risk factors may influence any of these variables. A model is proposed which links risk factors for overheating to the epidemiological distribution of sudden infant death syndrome. This model might account for the frequently reported association between formula-feeding and sudden infant death syndrome.

Body Temperature Regulation↗
PubMed1997

Total energy expenditure in 9 month and 12 month infants.

OBJECTIVES: To measure the total energy expenditure of 9 and 12 month old infants and compare with current recommendations for energy intake. DESIGN: Cross-sectional study. Total energy expenditure assessed using the doubly labelled water technique over a 10 d period. Classical anthropometric measurements taken. SETTING: Community based study in and around Cambridge, UK. SUBJECTS: Twenty infants aged 9 months of age and 20 infants aged 12 months of age recruited via local hospital birth records. MAIN OUTCOME MEASURES: Total energy expenditure calculated via the doubly labelled water technique. RESULTS: Measurements of total energy expenditure was successful in 34 cases. Mean total energy expenditure was 73.5 kcal/kg, 73.2 kcal/kg, 77.1 kcal/kg and 77.6 kcal/kg in the nine month old boys, nine month old girls, twelve month old boys and twelve month old girls respectively. These measurements are approximately 17% below current recommendations (FAO/WHO/UNU, 1985) at nine months of age and 22% below at one year of age. CONCLUSION: The data are consistent with findings in younger infants and older children in that the measurements of total energy expenditure are about 20-25% below current recommendations. It is unlikely that contemporary infants are being underfed and thus more likely that changes in feeding practices and modification of infant formula composition has led to the reduction in energy intake and energy expenditure in such infants.

Anthropometry↗
PubMed1997

Investigation of the relationship between infant temperament and later body composition.

OBJECTIVE: To investigate the ability of maternally-rated infant temperament to predict fatness and activity patterns in early childhood. DESIGN: Longitudinal investigation of infants studied at 12 weeks and followed up at 2-3.5 y of age. SUBJECTS: Thirty healthy full-term infants from the general population. MEASUREMENTS: Body composition, behavioural activity and temperament at 12 weeks; anthropometry, body composition, diet and behavioural activity at follow-up. RESULTS: Infant temperament predicted later behaviour and fatness. Easily soothable infants had leaner childhood skinfold thicknesses (P < 0.02) and were more active in childhood (P < 0.025). Infant distress was also related to childhood diet composition. CONCLUSIONS: Infant temperament can predict later body composition and behaviour. Both energy intake and energy expenditure may be mechanisms by which the relationship develops.

Age Factors↗
PubMed1997

Free-living energy expenditure and behaviour in late infancy.

OBJECTIVES: The energy requirements of infants are determined by body size, growth rate, and physical activity. Little is known of the determinants of energy expended on activity. The relation between free-living energy expenditure and behaviour was investigated in infants aged 9 and 12 months. METHODS: Total energy expenditure (TEE) was estimated by the doubly labelled water method and fat free mass was estimated from the 18O dilution space. Behaviour was assessed by two 24 hour activity diaries. SUBJECTS: Thirty four normal healthy infants. RESULTS: TEE was negatively related to the time spent feeding and negatively related to the time spent upset. Body size, represented by fat free mass, accounted for only 19% of the variation in TEE, whereas the combination of fat free mass and two behavioural variables explained 46% of the variation in TEE. CONCLUSIONS: Behaviour contributed significantly to TEE. The energy requirements of individual subjects in this age group cannot be predicted with accuracy from body size alone.

Anthropometry↗
PubMed1996

Comparison of measured sleeping metabolic rate and predicted basal metabolic rate in the first year of life.

In infants, sleeping metabolic rate (SMR) is used as a proxy for basal metabolic rate (BMR). BMR can be predicted from anthropometry using published equations. Our study was intended to evaluate the ability of these equations to predict measured SMR in infants aged 6 weeks to 12 months. SMR was measured in a mixed longitudinal study using the Douglas bag technique (n = 105). Measured SMR values were compared with BMR predicted from weight (BMR-1) or weight and length (BMR-2). These equations were not successful in predicting SMR in this age group. Percentage error of predicted BMR was related to infant weight (BMR-1: r = 0.26; p < 0.005; BMR-2: r = 0.18; p < 0.06). Alternative logarithmic equations were derived from this study (R = 0.84-0.87; SEE = 0.159-0.168). We conclude that the new equations, relating to contemporary infants, are more suitable but actual measurements remain preferred.

Anthropometry↗
PubMed1996

Dementing illnesses in rural populations: the need for research and challenges confronting investigators.

Expansion of the world's elderly populations has increased concerns about aging-related medical disorders like Alzheimer's disease and other dementias. In the United States, one fourth of those older than age 65 and at greatest risk for developing dementia live in rural environments that may influence its manifestation. The objectives of this study were to determine the need for and potential benefits of further epidemiological research concerning dementia and similar disorders in rural U.S. populations and to identify pertinent methodological issues related to rural dementia research. This study employed a National Library of Medicine (MEDLINE) document search based on the key words "cognitive disorders," "dementia," "Alzheimer's disease," and "rural," followed by recovery of literature resources references in the bibliographies of selected articles. Nineteen studies focusing on dementia or related disorders in rural settings have been reported from around the world. While four of these were conducted in the United States, only one rural dementia prevalence study has been undertaken in this country. Because of methodological variability, comparisons of prevalence estimates between these rural studies, as well as with those from urban investigations, is difficult. Nonetheless, there is reason to believe that certain potentially dementing illnesses are more common in rural populations. There is also evidence to suggest that the screening instruments commonly used in such studies tend to misclassify rural elders as "false positive" dementia cases. Information regarding dementing disorders, particularly Alzheimer's disease, in rural populations is scarce. Preliminary observations that dementia may be more common in rural settings and that rural families are more likely to maintain their dementing elders in the community imply that further rural dementia research could yield important insights into the risk factors for these illnesses, the variables influencing their course, and the methods by which they can be more effectively managed. A determination of the reliability and validity of commonly used dementia screening instruments in rural populations would represent an important advancement in this area of research.

Adaptation, Psychological↗