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J C K Wells

Publications and source records attributed to J C K Wells.

At least 19 recordsLinked to original sources
PubMed2006

A simplified approach to analysing bio-electrical impedance data in epidemiological surveys.

BACKGROUND: Bio-electrical impedance analysis (BIA) is widely used to estimate body composition. It is simple, quick and cheap, but less accurate than other methods. It has potential epidemiological value, but has conventionally required validation before application. AIMS: To develop a simple method of expressing weight, height and impedance data that avoids the need for population-specific validation equations in order to facilitate epidemiological application. METHODS: Body composition was measured using the four-component model in young adults (43 males, 90 females). Impedance (R) was measured hand-foot and foot-foot. Lean mass and fat mass were adjusted for height to give lean mass index (LMI) and fat mass index (FMI). Based on theoretical principles, we generated the index 1/R, which provides an index of body water adjusted for height. Sex-specific regression models were used to investigate the relationships between (a) 1/R and LMI, and (b) body mass index (BMI) adjusted for 1/R and FMI. The success of this approach was evaluated in relation to the conventional BIA approach, using correlation analysis. RESULTS: 1/R was a highly significant predictor of LMI. BMI adjusted for 1/R was a significant predictor of FMI. Our approach performed as well as the conventional approach for LMI, but not for FMI. DISCUSSION: Direct use of BIA data, rather than their combination with population-specific equations for the prediction of total body water, proved successful at ranking individuals of both sexes in terms of LMI and FMI. The index 1/R may prove particularly valuable in epidemiological studies where ranking of LMI is required.

Adipose Tissue↗
PubMed2006

Body composition in normal weight, overweight and obese children: matched case-control analyses of total and regional tissue masses, and body composition trends in relation to relative weight.

BACKGROUND: Childhood obesity is defined on the basis of weight and height, using body mass index (BMI). There is little detailed information on the body composition characteristic of overweight and obesity. OBJECTIVE: To evaluate total and regional body composition in overweight, obese and control children aged 7-14 years. DESIGN: Body composition was measured by the four-component model and dual X-ray absorptiometry in 38 age- and sex-matched pairs of obese and control children. Body composition trends were also evaluated by quintile of BMI standard deviation score (SDS) in these and 31 other children (n=107; BMI SDS range -1.0 to 4.3). RESULTS: Obese children were taller than controls (Delta=0.6 SDS; P=0.01) and had greater hydration of fat-free mass (FFM) (Delta=1.8 %, P<0.0001). After adjusting for these variables, obese children had greater FFM, fat mass (FM) and mineral (P<0.0001). Regional analyses showed that these differences were apparent in the arm, leg and trunk, but the three tissues had different proportional distributions of the excess. Fat was primarily in the trunk, but mineral in the leg. FM, FFM, hydration and mineral mass all increased across BMI SDS quintiles (P<0.0001), but the trend for FM was much the steepest. DISCUSSION: The greater weight of obese children is due to excess FFM including mineral as well as excess fatness. Increasing weight has a strong continuous relationship with increasing FM across the whole spectrum of weight.

Absorptiometry, Photon↗
PubMed2006

Measuring body composition.

Several aspects of body composition, in particular the amount and distribution of body fat and the amount and composition of lean mass, are now understood to be important health outcomes in infants and children. Their measurement is increasingly considered in clinical practice; however, paediatricians are often unsure as to which techniques are appropriate and suitable for application in specific contexts. This article summarises the pros and cons of measurement technologies currently available for paediatric application. Simple techniques are adequate for many purposes, and simple regional data may often be of greater value than "whole body" values obtained by more sophisticated approaches.

Absorptiometry, Photon↗
PubMed2005

A shift in the epidemiology of low body mass index in Brazilian adults.

OBJECTIVE: To study the prevalence and current predictors of low body mass index (BMI) in a population undergoing a rapid nutritional transition. DESIGN: Population-based cross-sectional study. SETTINGS: Individuals living in the urban area of Pelotas, a medium-sized southern Brazilian city, were interviewed at home. SUBJECTS: A multiple-stage sampling strategy was used. Out of 3372 eligible subjects, 3047 were interviewed. The study was restricted to adults (> or = 20 y). MAIN OUTCOME MEASURE: Low BMI was defined as <18.5 kg/m2. RESULTS: The prevalence of low BMI was 2.7% (95% confidence interval: 2.1; 3.3), higher in women than men (3.8 vs 1.3%; P < 0.001). In the whole sample (men and women combined), living without a partner and current smoking were positively associated with low BMI. Among women, low BMI presented a U-shaped relationship with age and was positively associated with educational level. The prevalence of low BMI in young women was 6.3%, and in highly educated young women was 8.9%. CONCLUSIONS: Consistently with previous Brazilian studies, a decline in the overall prevalence of low BMI is clear. However, differently from these studies, the predictors of low BMI in women are similar to those observed within developed countries (including low age and high education), possibly indicating an increase in eating disorders.

Adult↗
PubMed2005

Composition of the fat-free mass in obese and nonobese children: matched case-control analyses.

OBJECTIVE: Most body composition techniques assume constant properties of the fat-free mass (FFM), such as hydration, density and mineralisation. Previous studies suggested that FFM composition may change in childhood obesity; however, this issue has not been investigated in detail. AIM: To compare FFM composition in obese and nonobese children. DESIGN: Observational matched case-control analyses. SUBJECTS: A total of 28 obese children (13 boys, 15 girls) and 22 nonobese children (10 boys, 12 girls) aged 7-14 y. Obesity was defined as body mass index centile >95. METHODS: Measurements were made of weight, height, total body water, and body volume. Bone mineral content was estimated in a subsample. Body composition was calculated using three- and four-component models. RESULTS: According to the three-component model (n=22 matched pairs), obese children had greater hydration (P<0.05), and reduced density (P=0.057) of FFM. According to the four component model (n=11 pairs), obese children had greater hydration (P<0.01) and reduced density (P<0.002) of FFM. The mineralisation of FFM was increased, but not significantly so. CONCLUSION: The greater hydration and reduced density of FFM of obese children should be taken into account if body composition is to be measured with optimum accuracy during treatment programmes. These differences may be addressed by using multicomponent rather than two-component models of body composition. Although the greater mineralisation of FFM in obese children was not significant in the present study, the four-component model is best able to address the combined differences in hydration and mineralisation that occur in childhood obesity.

Absorptiometry, Photon↗
PubMed2005

Indices of whole-body and central adiposity for evaluating the metabolic load of obesity.

BACKGROUND: To assess the relative metabolic load or risk imposed by fatness, fat mass (FM) is commonly expressed as a proportion of weight (% fat), while central adiposity is assessed using the ratio of triceps (TRI) to subscapular (SUBS) skinfolds. The statistical validity of these indices, defined as independence of the index from its denominator, has received inadequate evaluation. OBJECTIVE: To critically examine commonly used obesity indices, and to propose more appropriate approaches. DESIGN: Cross-sectional studies. SUBJECTS: In total, 148 infants; 2195 adult men aged 18 y. METHODS: log-log regression analysis was used to explore the relationships between FM and weight (WT) or fat-free mass (FFM) (adults), and between TRI and SUBS (infants and adults). RESULTS: The simple indices FM/WT, FM/FFM, TRI/SUBS and SUBS/TRI remained related to their denominators, showing their rankings of individuals to be biased by size or fatness. The appropriate power (p) by which to raise the denominator was determined from regression analyses, and differed from unity in all cases. Both skinfold ratios showed a nonlinear relationship with their denominators. CONCLUSION: Simple indices for evaluating whole-body or central adiposity are statistically flawed, and remain influenced by size or fatness of the subject. The index FM/WT is conceptually flawed because FM appears in both numerator and denominator, and the index FM/FFM(p) is preferable. Skinfold ratios are also problematic, and to evaluate central adiposity SUBS alone, or SUBS/FFM(p), may represent more appropriate approaches. These issues should be investigated in other studies in order to address possible influences of age, ethnicity, gender and nutritional status.

Adipose Tissue↗
PubMed2005

Fetal, infant and childhood growth: relationships with body composition in Brazilian boys aged 9 years.

BACKGROUND: Early growth rate has been linked to later obesity categorised by body mass index (BMI), but the development of body composition has rarely been studied. METHODS: We tested the hypotheses that (1) birthweight and weight gain in (2) infancy or (3) childhood are associated with later body composition, in 172 Brazilian boys followed longitudinally since birth. Growth was assessed using measurements of weight and height at birth, 6 months, and 1 and 4 y. Measurements at 9 y comprised height, weight and body composition using foot-foot impedance. RESULTS: Birthweight was associated with later height and lean mass (LM), but not fatness. Weight gain 0-6 months was associated with later height and LM, and with obesity prevalence according to BMI, but not with fatness. Weight gain 1-4 y was associated with later fatness and LM. Weight gain 4-9 y was strongly associated with fatness but not LM. Early growth rate did not correlate positively with subsequent growth rate. CONCLUSIONS: Early rapid weight gain increased the risk of later obesity, but not through a direct effect on fatness. Childhood weight gain remained the dominant risk factor for later obesity. The reported link between early growth and later obesity may be due partly to hormonal programming, and partly to the contribution of LM to obesity indices based on weight and height. Whether our findings apply to other populations requires further research.

Birth Weight↗
PubMed2005

Assessing the acceptability and feasibility of the MEND Programme in a small group of obese 7-11-year-old children.

BACKGROUND AND AIMS: An uncontrolled, pilot study to evaluate feasibility and acceptability of a new community based childhood obesity treatment programme. METHODS: The mind, exercise, nutrition and diet (MEND) programme was held at a sports centre, twice-weekly, for 3 months. The programme consists of behaviour modification, physical activity and nutrition education. The primary outcome measure was waist circumference. Secondary outcomes were body mass index (BMI), cardiovascular fitness (heart rate, blood pressure and number of steps in 2 min), self-esteem and body composition. BMI of parents was also measured. See http://www.mendprogramme.org. RESULTS: Eleven obese children (7-11 years) and their families were recruited. Mean attendance was 78% (range 63-88%) with one drop out. Waist circumference, cardiovascular fitness and self-esteem were all significantly improved at 3 months and continued to improve at 6 months. BMI was significantly improved at 3 months but lost significance by 6 months. Deuterium studies showed a beneficial trend but were not significant. Of the 17 parents measured, seven were obese (BMI >/= 30) and eight overweight (BMI >/= 25). CONCLUSIONS: Although limited by the small number of participants and no control group, the MEND programme was acceptable to families and produced significant improvements in a range of risk factors associated with obesity that persisted over 3 months.

Body Mass Index↗
PubMed2005

Prediction of total body water in infants and children.

BACKGROUND: In paediatric clinical practice treatment is often adjusted in relation to body size, for example the calculation of pharmacological and dialysis dosages. In addition to use of body weight, for some purposes total body water (TBW) and surface area are estimated from anthropometry using equations developed several decades previously. Whether such equations remain valid in contemporary populations is not known. METHODS: Total body water was measured using deuterium dilution in 672 subjects (265 infants aged <1 year; 407 children and adolescents aged 1-19 years) during the period 1990-2003. TBW was predicted (a) using published equations, and (b) directly from data on age, sex, weight, and height. RESULTS: Previously published equations, based on data obtained before 1970, significantly overestimated TBW, with average biases ranging from 4% to 11%. For all equations, the overestimation of TBW was greatest in infancy. New equations were generated. The best equation, incorporating log weight, log height, age, and sex, had a standard error of the estimate of 7.8%. CONCLUSIONS: Secular trends in the nutritional status of infants and children are altering the relation between age or weight and TBW. Equations developed in previous decades significantly overestimate TBW in all age groups, especially infancy; however, the relation between TBW and weight may continue to change. This scenario is predicted to apply more generally to many aspects of paediatric clinical practice in which dosages are calculated on the basis of anthropometric data collected in previous decades.

Adolescent↗
PubMed2004

Number of days needed to assess energy and nutrient intake in infants and young children between 6 months and 2 years of age.

OBJECTIVE: To estimate the minimum number of days of recorded dietary intake needed to place infants and young children into thirds of a population distribution with an acceptable degree of accuracy. DESIGN: Dietary intake data collected from 5-day weighed food records for 72 infants and young children up to 2 y of age, collected during a cross-sectional study, were analysed to estimate the number of recording days necessary to assess intake of energy and 10 nutrients. SETTING: Community study among healthy infants and children. SUBJECTS: Parents attended recruitment sessions in local community areas. In total, 72 subjects were entered into the study and all completed the 5-day dietary assessment period. INTERVENTIONS: A 5-day weighed record of children's dietary intake was made by the parents or regular carer. RESULTS: Mean within subject standard deviations were smaller than mean between subject standard deviations with respect to energy (778 vs 824 kJ/day), macronutrient subclasses: protein (8 vs 9.4 g/day); fat (9 vs 10 g/day); and carbohydrate (26 vs 29 g/day) and for specific micronutrients: calcium (163 vs 236 mg/day); phosphorus (143 vs 270 mg/day); magnesium (25 vs 43 mg/day); iron (2 vs 3 mg/day); zinc (1 vs 1.3 mg/day); ascorbic acid (27 vs 64 mg/day) and retinol equivalents (281 vs 424 microg/day). Estimated number of days of food records necessary to assess intake of energy, protein, fat and carbohydrate with acceptable degree of accuracy were 5,4,4 and 3, respectively. For all the micronutrients included in this analysis 2 days of recording were necessary. CONCLUSION: Compared with adults and older children, fewer days are needed to classify this age group into thirds of the distribution with an acceptable degree of accuracy according to intake of energy and specific nutrients. SPONSORSHIP: The data collection phase of this study was supported by a grant from the Procter and Gamble Company, Cincinnati, OH, USA.

Age Factors↗
PubMed2003

Centile reference charts for total energy expenditure in infants from 1 to 12 months.

BACKGROUND: A knowledge of energy expenditure in infancy is required for the estimation of recommended daily amounts of food energy, for designing artificial infant feeds, and as a reference standard for studies of energy metabolism in disease states. OBJECTIVES: The objectives of this study were to construct centile reference charts for total energy expenditure (TEE) in infants across the first year of life. METHODS: Repeated measures of TEE using the doubly labeled water technique were made in 162 infants at 1.5, 3, 6, 9 and 12 months. In total, 322 TEE measurements were obtained. The LMS method with maximum penalized likelihood was used to construct the centile reference charts. Centiles were constructed for TEE expressed as MJ/day and also expressed relative to body weight (BW) and fat-free mass (FFM). RESULTS: TEE increased with age and was 1.40,1.86, 2.64, 3.07 and 3.65 MJ/day at 1.5, 3, 6, 9 and 12 months, respectively. The standard deviations were 0.43, 0.47, 0.52,0.66 and 0.88, respectively. TEE in MJ/kg increased from 0.29 to 0.36 and in MJ/day/kg FFM from 0.36 to 0.48. CONCLUSIONS: We have presented centile reference charts for TEE expressed as MJ/day and expressed relative to BW and FFM in infants across the first year of life. There was a wide variation or biological scatter in TEE values seen at all ages. We suggest that these centile charts may be used to assess and possibly quantify abnormal energy metabolism in disease states in infants.

Administration, Oral↗
PubMed2003

Breast milk and energy intake in exclusively, predominantly, and partially breast-fed infants.

OBJECTIVE: To investigate the extent to which breast milk is replaced by intake of other liquids or foods, and to estimate energy intake of infants defined as exclusively (EBF), predominantly (PBF) and partially breast-fed (PartBF). DESIGN: Cross-sectional. SETTING: Community-based study in urban Pelotas, Southern Brazil. SUBJECTS: A total of 70 infants aged 4 months recruited at birth. MAIN OUTCOME MEASURES: Breast milk intake measured using a "dose-to-the-mother" deuterium-oxide turnover method; feeding pattern and macronutrient intake assessed using a frequency questionnaire. RESULTS: Adjusted mean breast milk intakes were not different between EBF and PBF (EBF, 806 g/day vs PBF, 778 g/day, P=0.59). The difference between EBF and PartBF was significant (PartBF, 603 g/day, P=0.004). Mean intakes of water from supplements were 10 g/day (EBF), 134 g/day (PBF) and 395 g/day (PartBF). Compared to EBF these differences were significant (EBF vs PBF, P=0.005; EBF vs PartBF, P<0.001). The energy intake of infants receiving cow or formula milk (BF+CM/FM) in addition to breast milk tended to be 20% higher than the energy intake of EBF infants (EBF, 347 kJ/kg/day vs BF+CM/FM, 418 kJ/kg/day, P=0.11). CONCLUSIONS: There was no evidence that breast milk was replaced by water, tea or juice in PBF compared to EBF infants. The energy intake in BF+CM/FM infants tended to be 20% above the latest recommendations (1996) for breast-fed and 9% above those for formula-fed infants. If high intakes are maintained, this may result in obesity later in life. SPONSORSHIP: International Atomic Energy Agency through RC 10981/R1.

Bottle Feeding↗
PubMed2003

Evaluation of air-displacement plethysmography in children aged 5-7 years using a three-component model of body composition.

The aim of the present study was to evaluate air-displacement plethysmography (ADP) in children aged 5-7 years. Body-composition measurements were obtained by ADP, (2)H dilution and anthropometry in twenty-eight children. Calculation of body volume by ADP was undertaken using adult and children's equations for predicting lung volume and surface area. Fat-free mass (FFM) was calculated using a three-component model. Measured FFM hydration was then compared with values from the reference child. Differences between measured and reference hydration were back-extrapolated, to calculate the error in ADP that would account for any disagreement. Propagation of error was used to distinguish the contributions of methodological precision and biological variability to total hydration variability. The use of children's equations influenced the results for lung volume but not surface area. The mean difference between measured and reference hydration was 0.6 (sd 1.7) % (P<0.10), equivalent to an error in body volume of 0.04 (sd 0.20) litres (P<0.30), and in percentage fat of 0.4 (sd 1.9) (P<0.28). The limits of agreement in individuals could be attributed to methodological precision and biological variability in hydration. It is concluded that accuracy of ADP was high for the whole group, with a mean bias of <0.5 % fat using the three-component model, and after taking into account biological variability in hydration, the limits of agreement were around +/-2 % fat in individuals. Paediatric rather than adult equations for lung volume estimation should be used.

Body Composition↗
PubMed2003

Body composition in childhood: effects of normal growth and disease.

Body composition in children is of increasing interest within the contexts of childhood obesity, clinical management of patients and nutritional programming as a pathway to adult disease. Energy imbalance appears to be common in many disease states; however, body composition is not routinely measured in patients. Traditionally, clinical interest has focused on growth or nutritional status, whereas more recent studies have quantified fat mass and lean mass. The human body changes in proportions and chemical composition during childhood and adolescence. Most of the weight gain comprises lean mass rather than fat. In general, interest has focused on percentage fat, and less attention has been paid to the way in which lean mass varies within and between individuals. In the general population secular trends in BMI have been widely reported, indicating increasing levels of childhood obesity, which have been linked to reduced physical activity. However, lower activity levels may potentially lead not only to increased fatness, but also to reduced lean mass. This issue merits further investigation. Diseases have multiple effects on body composition and may influence fat-free mass and/or fat mass. In some diseases both components change in the same direction, whereas in other diseases, the changes are contradictory and may be concealed by relatively normal weight. Improved techniques are required for clinical evaluations. Both higher fatness and reduced lean mass may represent pathways to an increased risk of adult disease.

Adipose Tissue↗
PubMed2002

Segmental bioelectrical impedance analysis in children aged 8-12 y: 1. The assessment of whole-body composition.

OBJECTIVES: To investigate the potential of segmental bioelectrical impedance analysis (BIA) for estimating whole-body composition in children. DESIGN: Strengths of relationships were determined between indices of impedance or specific resistivities of body segments and reference four-component model (4-CM) assessments of body composition. SUBJECTS: Eighteen boys and 19 girls aged 8-12 y. MEASUREMENTS: Whole-body and segment BIA and anthropometry were used to calculate impedance indices of the whole body and segments and specific resistivities of segments; total body water (TBW), fat-free mass (FFM) and body fat were assessed using the 4-CM. RESULTS: Segmental BIA indices were significantly related to body composition, provided that appropriate comparisons were undertaken for each index: impedance adjusted for unit segment length was better related to TBW and FFM, whereas segment specific resistivity was better related to body fat. Differences between body composition estimates obtained with the 4-CM and predicted using BIA were partly dependent on limb-to-trunk ratios of BIA indices. CONCLUSION: Segmental BIA has potential for providing additional alternative approaches to the assessment of whole-body composition in children: (a) FFM and TBW were best related to impedance adjusted for segment length; (b) body fat was best related to segment specific resistivity; and (c) the relative influences of different segment BIA indices may be utilisable for generating more valid whole-body composition estimates.

Adipose Tissue↗
PubMed2002

Segmental bioelectrical impedance analysis in children aged 8-12 y: 2. The assessment of regional body composition and muscle mass.

OBJECTIVES: To investigate the potential of segmental bioelectrical impedance analysis (BIA) for assessing regional composition and muscle mass in children. DESIGN: Strengths of relationships were determined between (a) BIA indices of trunk, limbs or limb segments and (b) segment fat or fat-free mass (FFM) assessed using dual-energy X-ray absorptiometry (DXA); the extent of agreement was established between two independent models, based on DXA and BIA, of limb muscle and adipose tissue (AT) mass. SUBJECTS: Eighteen boys and 19 girls aged 8-12 y. MEASUREMENTS: BIA and anthropometry of trunk, whole limbs, limb segments and defined sections were used to calculate segmental impedance indices and specific resistivities; segment fat and FFM were obtained using DXA; muscle and AT masses of limbs, segments and sections were estimated using DXA and BIA models, and by anthropometry. RESULTS: Segmental BIA indices were significantly related to composition of the segments assessed using DXA; although substantial bias was observed, there was fairly good agreement (low 95% limits of agreement) between the BIA and DXA models of muscle mass and estimates from each were similarly categorised in tertiles, as were estimates of AT. CONCLUSION: Segmental BIA appears to have potential for assessing in children the composition of body segments, as obtained using DXA, and the masses of muscle and AT in whole limbs, limb segments and defined sections.

Absorptiometry, Photon↗
PubMed2002

Adjustment of fat-free mass and fat mass for height in children aged 8 y.

OBJECTIVE: To explore the relationships between height and (a) fat-free mass (FFM) and (b) fat mass (FM) in children in order to determine the optimum means of adjusting body composition for height. DESIGN: Cross-sectional study. SUBJECTS: Sixty-nine children aged 8 y. MEASUREMENTS AND METHODS: Weight and height (HT) were measured, and total body water by deuterium dilution for estimation of fat-free mass and fat mass. The indices FFM/HT(2) and FM/HT(2) were calculated, as were the indices FFM/HT(p) and FM/HT(p) where P was selected in order to eliminate the correlation of these indices with height. RESULTS: FFM was optimally adjusted for height by calculating FFM/HT(2). FM was optimally adjusted by calculating FM/HT(6). However, height accounted for <8% of the variation in FM/HT(2), indicating that the bias of this simpler index is small. CONCLUSIONS: Different adjustments of FFM and FM for height are possible, depending on the study design. The indices FFM/HT(2) and FM/HT(2) are appropriate for many purposes, and have the advantage of expressing both aspects of body composition in common units. However, in some scenarios a more sophisticated approach is required for evaluating body fatness.

Adipose Tissue↗