Antony Wright

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.

Is it possible to assess free-living physical activity and energy expenditure in young people by self-report?

BACKGROUND It is unclear whether it is possible to accurately estimate physical activity energy expenditure (PAEE) by self-report in youth. OBJECTIVE We assessed the validity and reliability of 4 self-reports to assess PAEE and time spent at moderate and vigorous intensity physical activity (MVPA) over the previous week in British young people between 4 and 17 y of age. DESIGN PAEE and MVPA were derived from the Childrens Physical Activity Questionnaire, Youth Physical Activity Questionnaire, and Swedish Adolescent Physical Activity Questionnaire; a lifestyle score indicative of habitual activity was derived from the Child Heart and Health Study in England Questionnaire. These data were compared with criterion methods, PAEE, and MVPA derived from simultaneous measurements by doubly labeled water and accelerometry in 3 age groups: 4-5 y (n = 27), 12-13 y (n = 25), and 16-17 y (n = 24). Validity was assessed by using Spearman correlations and the Bland-Altman method, and reliability was assessed by using intraclass correlation coefficients. RESULTS The strength of association between questionnaire and criterion methods varied (r = 0.09 to r = 0.46). Some questionnaires were able to accurately assess group-level PAEE and MVPA for some age groups, but the error was large for individual-level estimates throughout. Reliability of the Youth Physical Activity Questionnaire and Child Heart and Health Study in England Questionnaire was good (intraclass correlation coefficient: 0.64-0.92). CONCLUSIONS Absolute PAEE and MVPA estimated from these self-reports were not valid on an individual level in young people, although some questionnaires appeared to rank individuals accurately. Age (the outcome of interest) and whether individual or group-level estimates are necessary will influence the best choice of self-report method when assessing physical activity in youth.

Accuracy and validity of a combined heart rate and motion sensor for the measurement of free-living physical activity energy expenditure in adults in Cameroon

BACKGROUND The increasing burden of non-communicable diseases in sub-Saharan Africa (SSA) warrants rigorous studies of contributing lifestyle factors. Combined heart rate (HR) and movement monitoring make it possible to objectively measure physical activity in free-living individuals. We examined the validity of a combined HR and motion sensor in estimating physical activity energy expenditure (PAEE) in free-living adults in rural and urban Cameroon compared with doubly-labelled water (DLW) as criterion. METHODS PAEE was measured in 33 free-living rural and urban dwellers by DLW over 7 consecutive days. Simultaneously, the combined sensor recorded HR and uni-axial acceleration. Individual HR vs PAEE calibration was done by a step test. Branched equation modelling was used to estimate PAEE from HR and acceleration. Validity and accuracy of prediction were expressed as mean bias and root mean square error (RMSE). Agreement was analysed using Bland and Altman limits of agreement (LOA). RESULTS There was no significant mean bias between PAEE estimated from the combined sensor or measured by DLW [mean bias (standard error): -5.4 (5.1) kJ/kg/day; P = 0.3; RMSE = 29.3 kJ/kg/day]. The bias doubled for group compared with individual calibration of HR [-9.1 (5.0) kJ/kg/day, P = 0.08]. PAEE prediction was more accurate in urban compared with rural volunteers. The 95% LOAs between predicted and measured PAEE were ∼50-60 kJ/kg/day above or below perfect agreement. CONCLUSIONS Combined HR and movement sensing is a valid method for estimating free-living PAEE on group level in adults in SSA.

Estimation of Daily Energy Expenditure in Pregnant and Non-Pregnant Women Using a Wrist-Worn Tri-Axial Accelerometer

Background Few studies have compared the validity of objective measures of physical activity energy expenditure (PAEE) in pregnant and non-pregnant women. PAEE is commonly estimated with accelerometers attached to the hip or waist, but little is known about the validity and participant acceptability of wrist attachment. The objectives of the current study were to assess the validity of a simple summary measure derived from a wrist-worn accelerometer (GENEA, Unilever Discover, UK) to estimate PAEE in pregnant and non-pregnant women, and to evaluate participant acceptability. Methods Non-pregnant (N = 73) and pregnant (N = 35) Swedish women (aged 20–35 yrs) wore the accelerometer on their wrist for 10 days during which total energy expenditure (TEE) was assessed using doubly-labelled water. PAEE was calculated as 0.9×TEE-REE. British participants (N = 99; aged 22–65 yrs) wore accelerometers on their non-dominant wrist and hip for seven days and were asked to score the acceptability of monitor placement (scored 1 [least] through 10 [most] acceptable). Results There was no significant correlation between body weight and PAEE. In non-pregnant women, acceleration explained 24% of the variation in PAEE, which decreased to 19% in leave-one-out cross-validation. In pregnant women, acceleration explained 11% of the variation in PAEE, which was not significant in leave-one-out cross-validation. Median (IQR) acceptability of wrist and hip placement was 9(8–10) and 9(7–10), respectively; there was a within-individual difference of 0.47 (p<.001). Conclusions A simple summary measure derived from a wrist-worn tri-axial accelerometer adds significantly to the prediction of energy expenditure in non-pregnant women and is scored acceptable by participants.

Secular trends in under-reporting in young people

National survey data show that reported energy intake has decreased in recent decades despite a rise in the prevalence of obesity. This disparity may be due to a secular increase in under-reporting or a quantitatively greater decrease in energy expenditure. This study examines the extent of under-reporting of energy intake in the National Diet and Nutrition Survey (NDNS) in young people aged 4-18 years in 1997 using published equations to calculate estimated energy requirements. It explores secular changes by comparison with the Diets of British School Children (DBSC) survey in 10-11- and 14-15-year-olds in 1983. In the NDNS, under-reporting (estimated energy requirements--energy intake) represented 21 % of energy needs in girls and 20 % in boys. The magnitude of under-reporting increased significantly with age (P<0.001) and was higher in overweight than lean individuals over 7 years of age. To compare reported energy intake in DBSC and NDNS, the estimated physical activity level from dietary records (dPAL=reported energy intake/predicted BMR) was calculated. If there were no under-reporting, dPAL would represent the subjects true activity level. However, dPAL from the NDNS was significantly lower than that from the DBSC by 8 % and 9 % in boys and girls for those aged 10-11 years, and by 14 % and 11 % for 14-15-year-olds respectively, reaching physiologically implausible levels in the 14-15-year-old girls (dPAL=1.17). If activity levels have remained constant between the two surveys, under-reporting has increased by 8-14 %. The evidence supports a secular trend towards increased under-reporting between the two surveys, but the precise magnitude cannot be quantified in the absence of historical measures of energy expenditure.

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.

Validation of a quantitative magnetic resonance method for measuring human body composition.

Objective: To evaluate a novel quantitative magnetic resonance (QMR) methodology (EchoMRI‐AH, Echo Medical Systems) for measurement of whole‐body fat and lean mass in humans.

Assessment of volume depletion in children with malaria.

ABSTRACT Background The degree of volume depletion in severe malaria is currently unknown, although knowledge of fluid compartment volumes can guide therapy. To assist management of severely ill children, and to test the hypothesis that volume changes in fluid compartments reflect disease severity, we measured body compartment volumes in Gabonese children with malaria. Methods and Findings Total body water volume (TBW) and extracellular water volume (ECW) were estimated in children with severe or moderate malaria and in convalescence by tracer dilution with heavy water and bromide, respectively. Intracellular water volume (ICW) was derived from these parameters. Bioelectrical impedance analysis estimates of TBW and ECW were calibrated against dilution methods, and bioelectrical impedance analysis measurements were taken daily until discharge. Sixteen children had severe and 19 moderate malaria. Severe childhood malaria was associated with depletion of TBW (mean [SD] of 37 [33] ml/kg, or 6.7% [6.0%]) relative to measurement at discharge. This is defined as mild dehydration in other conditions. ECW measurements were normal on admission in children with severe malaria and did not rise in the first few days of admission. Volumes in different compartments (TBW, ECW, and ICW) were not related to hyperlactataemia or other clinical and laboratory markers of disease severity. Moderate malaria was not associated with a depletion of TBW. Conclusions Significant hypovolaemia does not exacerbate complications of severe or moderate malaria. As rapid rehydration of children with malaria may have risks, we suggest that fluid replacement regimens should aim to correct fluid losses over 12–24 h.

Use of bioelectrical impedance analysis to assess body composition in rural Gambian children.

Objective:To validate the Tanita BC-418MA Segmental Body Composition Analyser and four-site skinfold measurements for the prediction of total body water (TBW), percentage fat-free mass (%FFM) and percentage body fat (%BF) in a population of rural Gambian children.Subjects/Methods:One hundred and thirty-three healthy Gambian children (65 males and 68 females). FFM estimated by the inbuilt equations supplied with the Tanita system was assessed by comparison with deuterium oxide dilution and novel prediction equations were produced. Deuterium oxide dilution was also used to develop equations for %BF based on four-site skinfolds (biceps, triceps, subscapular and suprailiac).Results:The inbuilt equations underestimated FFM compared to deuterium oxide dilution in all the sex and age categories (P<0.003), with greater accuracy in younger children and in males. The best prediction of %FFM was obtained from the variables height, weight, sex, impedance, age and four skinfold thickness measurements (adjusted R 2=0.84, root mean square error (MSE)=2.07%).Conclusions:These data suggest that the Tanita instrument may be a reliable field assessment technique in African children, when using population and gender-specific equations to convert impedance measurements into estimates of FFM.

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 childrens 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 childrens 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.