Relation between physical activity and energy expenditure in a representative sample of young children

Dose response association of pregnancy cigarette smoke exposure, childhood stature, overweight and obesity

BACKGROUND

The combined dose response effects of pregnancy cigarette smoke exposure on childhood overweight, obesity and short stature have not been reported.

METHOD

A community based cross-sectional survey of 3038 children aged 5-11 years from 15 primary schools in Merseyside, UK. Self-completed parental questionnaires were used for family characteristics, socio-economic status and parental smoking practices. Children were measured for height and weight and z-scores calculated for parental smoking categories.

RESULTS

Of 689 (34.0%) mothers who smoked during pregnancy 50.5% smoked ten or more cigarettes daily (heavy smokers). Children of maternal non-smokers had prevalence estimates for overweight, obesity and short stature of 25, 9.6 and 3.2%, respectively. Prevalence estimates were higher in children of mothers who were heavy smokers during pregnancy, 31.5% (P = 0.001), 15.6% (P < 0.001) and 5.5% (P = 0.001), respectively. Mean height for age z-scores was lower among heavy maternal (P < 0.001) and paternal smokers (P < 0.01) compared to non-smokers. Childhood overweight, obesity or short stature were all associated with heavy maternal smoking during pregnancy (all P < 0.001). Mean body mass index (BMI) z-scores were higher in boys of mothers who smoked (P = 0.043). The adjusted odds ratio for short stature in children of heavy maternal smokers was 2.76 (95% CI 1.21-6.33) and 4.28 (1.37-13.37) if both parents were heavy smokers. The adjusted OR for obesity in children of maternal smokers was 1.61(1.19-2.18). The population attributable risk for short stature was 8.8% (1.1-22.7) for heavy maternal smokers.

CONCLUSION

A dose-response association was observed between pregnancy smoking exposure, short stature and obesity.

Correlates of sedentary behaviours in preschool children: a review

BACKGROUND

Sedentary behaviour has been linked with a number of health outcomes. Preschool-aged children spend significant proportions of their day engaged in sedentary behaviours. Research into the correlates of sedentary behaviours in the preschool population is an emerging field, with most research being published since 2002. Reviews on correlates of sedentary behaviours which include preschool children have previously been published; however, none have reported results specific to the preschool population. This paper reviews articles reporting on correlates of sedentary behaviour in preschool children published between 1993 and 2009.

METHODS

A literature search was undertaken to identify articles which examined correlates of sedentary behaviours in preschool children. Articles were retrieved and evaluated in 2008 and 2009.

RESULTS

Twenty-nine studies were identified which met the inclusion criteria. From those studies, 63 potential correlates were identified. Television viewing was the most commonly examined sedentary behaviour. Findings from the review suggest that child's sex was not associated with television viewing and had an indeterminate association with sedentary behaviour as measured by accelerometry. Age, body mass index, parental education and race had an indeterminate association with television viewing, and outdoor playtime had no association with television viewing. The remaining 57 potential correlates had been investigated too infrequently to be able to draw robust conclusions about associations.

CONCLUSIONS

The correlates of preschool children's sedentary behaviours are multi-dimensional and not well established. Further research is required to provide a more comprehensive understanding of the influences on preschool children's sedentary behaviours to better inform the development of interventions.

Validation of cross-sectional time series and multivariate adaptive regression splines models for the prediction of energy expenditure in children and adolescents using doubly labeled water

Accurate, nonintrusive, and inexpensive techniques are needed to measure energy expenditure (EE) in free-living populations. Our primary aim in this study was to validate cross-sectional time series (CSTS) and multivariate adaptive regression splines (MARS) models based on observable participant characteristics, heart rate (HR), and accelerometer counts (AC) for prediction of minute-by-minute EE, and hence 24-h total EE (TEE), against a 7-d doubly labeled water (DLW) method in children and adolescents. Our secondary aim was to demonstrate the utility of CSTS and MARS to predict awake EE, sleep EE, and activity EE (AEE) from 7-d HR and AC records, because these shorter periods are not verifiable by DLW, which provides an estimate of the individual's mean TEE over a 7-d interval. CSTS and MARS models were validated in 60 normal-weight and overweight participants (ages 5-18 y). The Actiheart monitor was used to simultaneously measure HR and AC. For prediction of TEE, mean absolute errors were 10.7 +/- 307 kcal/d and 18.7 +/- 252 kcal/d for CSTS and MARS models, respectively, relative to DLW. Corresponding root mean square error values were 305 and 251 kcal/d for CSTS and MARS models, respectively. Bland-Altman plots indicated that the predicted values were in good agreement with the DLW-derived TEE values. Validation of CSTS and MARS models based on participant characteristics, HR monitoring, and accelerometry for the prediction of minute-by-minute EE, and hence 24-h TEE, against the DLW method indicated no systematic bias and acceptable limits of agreement for pediatric groups and individuals under free-living conditions.

Daily physical activity in japanese preschool children evaluated by triaxial accelerometry: the relationship between period of engagement in moderate-to-vigorous physical activity and daily step counts

The purpose of the present study was to evaluate moderate-to-vigorous physical activity using triaxial accelerometry in Japanese preschool children. The relationship between daily step counts as a convenient measure of physical activity and minutes of engagement in moderate-to-vigorous physical activity was also examined. Physical activity was assessed using a triaxial accelerometer (ActivTracer, GMS) and daily steps using a uniaxial accelerometer for 6 consecutive days, including weekdays and weekend days, in 157 four- to six-year-old Japanese children attending kindergarten or nursery school. Using triaxial and uniaxial accelerometers, nonlocomotive activities and step counts for young children can be evaluated, respectively. Average daily moderate-to-vigorous physical activity (physical activity ratio >or=3) and step counts were 102 (+/-32) min/day and 13,037 (+/-2,846) steps/day, respectively. A strong and significant correlation was observed between minutes of moderate-to-vigorous physical activity and step counts (r=0.832, p<0.001). The daily step counts corresponding to 60 min, 100 min, and 120 min of moderate-to-vigorous physical activity were 9,934, 12,893, and 14,373 steps/day, respectively. The correlation coefficient between minutes of higher intensity activities (physical activity ratio >or=4) and step counts was slightly lower (r=0.604, p<0.001). The daily step count corresponding to 30 min of the higher intensity activities was 14,768 steps/day. These results suggest that approximately 13,000 steps/day are required for preschool children to engage in more than 100 min of moderate-to-vigorous physical activity.

Physical activity of children in family child care

Physical activity was monitored for 65 boys and girls, during family child care, using accelerometry. Average accelerometer wear time was 7.0 h (SD = 0.83), and average counts per epoch were 104.6 (SD = 31.6). Mean minutes per hour of moderate-vigorous physical activity and sedentary behaviour were 1.76 min (SD = 0.90) and 39.49 min (SD = 4.50), respectively. The very low levels of moderate-vigorous physical activity suggest that the young children in this study may be insufficiently active during child care.

Relationship between physical activity measured using accelerometers and energy expenditure measured using doubly labelled water in Indian children

BACKGROUND/OBJECTIVES

To test the association between physical activity measured using accelerometer counts (Actigraph) and energy expenditure (EE) measured using the doubly labelled water (DLW) method in free-living children in India. The aim of this study was to explore the usefulness of Actigraphs in estimating EE.

SUBJECTS/METHODS

Total EE (TEE) was measured in 58 children aged 8-9 years over a period of 2 weeks using the DLW technique. Physical activity level (PAL) was estimated from TEE, and the basal metabolic rate was predicted from weight. Physical activity was measured simultaneously using the Actigraph accelerometers (MTI AM7164 and GT1M). TEE was also calculated from the Actigraph counts using a published equation.

RESULTS

TEE (mean: 6.6 vs 5.7 MJ, P=0.04) and Actigraph counts (counts/minute: 557 vs 465, P=0.02; total counts: 445 534 vs 354 748, P=0.004) were higher in boys than in girls. There were no significant correlations between either total Actigraph counts (r=0.15, P=0.3) or counts/minute (r=0.18, P=0.2), and TEE estimated using DLW. Similarly, there were no significant correlations between Actigraph counts and PAL (r=0.10, P=0.5; r=0.17, P=0.2, respectively). The Bland-Altman analysis showed poor agreement between TEE estimated using the DLW method and TEE derived from the Actigraph equation.

CONCLUSIONS

Activity measured using Actigraph accelerometers was not related to TEE and PAL derived using the DLW technique in children in Mysore. Actigraphs may not be useful in predicting EE in this setting, but may be better used for judging activity patterns.

Childhood obesity: A comparison of health habits of middle-school students from two communities

Objective:

To assess whether children’s diet and physical activity patterns differ between neighboring communities with differing resources.

Study design and setting:

We compared the health behaviors of middle-school students in two Michigan communities; Ann Arbor and Ypsilanti; median household income of US$46,299 and 28,610, respectively. Self-reported diet and physical activity habits were collected.

Participants:

A total of 733 middle-school students from two neighboring communities (five Ann Arbor and two Ypsilanti middle schools) participated in the study.

Measures:

Data on age, gender, and racial/ethnic factors were collected as part of the baseline assessment. Students were also measured for height and weight. Body mass index was calculated. Information on diet and physical activity in addition to amounts and types of sedentary activities was assessed via questionnaires.

Results:

More Ypsilanti schoolchildren were obese compared to the Ann Arbor schoolchildren (22.2% vs 12.6%; P = 0.01). The Ypsilanti schoolchildren reported higher consumption of fried meats (7.5% vs 3.2%; P = 0.02), French fries or chips (14.3% vs 7.9%; P = 0.02), punch or sports drinks (24.1% vs 12.2%; P = 0.001) and soda (18% vs 7.9%; P < 0.001) compared to the Ann Arbor children. School-based activities including physical education classes (58.6% vs 89.7%; P < 0.001) and sports teams (34.6% vs 62.8%; P < 0.001) differed for Ypsilanti schoolchildren vs Ann Arbor children. Sedentary behaviors were higher in the Ypsilanti children.

Conclusions:

Differences in diet and physical activity habits among children from two neighboring communities with varying resources suggests a need for school-based interventions to promote healthy behaviors among middle-school students.

Validity and reproducibility of motion sensors in youth: a systematic update

PURPOSE

To review recently published studies on the reproducibility, validity, and feasibility of motion sensors used to assess physical activity in healthy children and adolescents (2-18 yr).

METHODS

On October 2004, a systematic literature search in PubMed, EMBASE, and PsycINFO was performed. This search has been updated on October 2007. In this update, the clinimetric quality of three pedometers (Digi-Walker, Walk4Life, and Sun TrekLINQ) and nine accelerometers (ActiGraph, BioTrainer, StepWatch Activity Monitor, Actiwatch, Actical, Tritrac-R3D, RT3, ActivTracer, and Mini-Motionlogger) has been evaluated and compared using a checklist.

RESULTS

Thirty-two recently published clinimetric studies have been reviewed. All 12 motion sensors have been validated in youth in one or more studies. There is strong evidence for moderate validity of the StepWatch in children and adolescents (4-18 yr) and moderate to good validity of the ActiGraph in preschool children and young children (2-8 yr). There is less evidence for the reproducibility and feasibility of the 12 motion sensors. Strong evidence exists for good reproducibility of the ActiGraph in preschool children (2-4 yr).

CONCLUSION

Compared to the review performed in 2004, there is increased evidence for the clinimetric quality of pedometers and accelerometers in youth. Most motion sensors seem reproducible, valid, and feasible in assessing physical activity in youth.

Increasing school playground physical activity: a mixed methods study combining environmental measures and children's perspectives

Schools are integral settings in which children can participate in moderate and vigorous physical activity. This study reports on the relationship between playground characteristics and child activity levels using a combination of quantitative and qualitative methods. The aim of the study is to increase understanding of how children respond to their school playground environments. Twenty-three primary schools located in a predominantly low socio-economic area of Melbourne, Australia were involved. SOPLAY (System for Observing Play and Leisure Activity in Youth) was administered in all 23 schools to measure the levels of student physical activity and playground environmental factors such as equipment provision. In 12 of the 23 schools, a sample of 9-11-year-old students participated in focus group discussions exploring perceptions of their school playgrounds using a photo ordering technique. A larger proportion of students participated in VPA when loose equipment (60% vs. 52%; p<0.001) and teacher supervision (62% vs. 52%; p<0.001) were present in activity settings, compared to when they were unavailable. Fixed play equipment and bitumen with court/play-line markings were seen by children as settings inviting active play but only had the greatest impact on moderate activity (fixed play equipment: 35% vs. 20%, p<0.001; court markings/goals: 62% vs. 52%, p<0.001; play-line markings: 25% vs. 20%, p=0.04). The mixed method design provided a greater understanding of the potential influence of environmental characteristics on children's lunch time activity levels and their perceptions of play areas. The findings indicate that relatively simple changes such as the provision of loose equipment, painting of court and play-line markings, and increased teacher presence on the playground, are likely to provide opportunities for increased physical activity.

An exploratory study of after-school sedentary behaviour in elementary school-age children with intellectual disability

BACKGROUND

The purpose of this study was both to investigate if children with intellectual disability (ID) spend more time watching television and on the computer than their peers without disabilities and if total screen time correlates with physical activity in these same children.

METHODS

Participants were 9 children with ID matched with 9 children without ID, aged 7-12 years. Participants were matched by gender, age, and body mass index (BMI). Parents logged after-school television and computer time. Physical activity was recorded with accelerometers.

RESULTS

Mann-Whitney tests revealed no difference between television or computer time between the groups. Correlations between physical activity and screen time revealed that children without ID had a low relationship between physical activity and screen time (tau = -.11, p = .64). Conversely, children with ID had a moderate relationship between physical activity and screen time (tau = .56, p = .04).

CONCLUSIONS

These results suggest that there might be different patterns of sedentary behaviours between children with and without ID, indicating that unique interventions may be needed for individuals with ID.

Methodological considerations in using accelerometers to assess habitual physical activity in children aged 0-5 years

This paper reviews the evidence behind the methodological decisions accelerometer users make when assessing habitual physical activity in children aged 0-5 years. The purpose of the review is to outline an evidence-guided protocol for using accelerometry in young children and to identify gaps in the evidence base where further investigation is required. Studies evaluating accelerometry methodologies in young children were reviewed in two age groups (0-2 years and 3-5 years) to examine: (i) which accelerometer should be used, (ii) where the accelerometer should be placed, (iii) which epoch should be used, (iv) how many days of monitoring are required, (v) how many minutes of monitoring per day are required, (vi) how data should be reduced, (vii) which cut-point definitions for identifying activity intensity should be used, and (viii) which physical activity outcomes should be reported and how. Critique of the available evidence provided a basis for the development of a recommended users protocol in 3-5-year olds, although several issues require further research. Because of the absence of methodological studies in children under 3 years, a protocol for the use of accelerometers in this age range could not be specified. Formative studies examining the utility, feasibility and validity of accelerometer-based physical activity assessments are required in children under 3 years of age. Recommendations for further research are outlined, based on the above findings, which, if undertaken, will enhance the accuracy of accelerometer-based assessments of habitual physical activity in young children.

Using heart-rate feedback to increase physical activity in children

OBJECTIVE

The objective of this study was to test whether heart-rate feedback prompts increased physical activity (PA) in primary school students.

METHODS

A controlled trial with 210 9-11 year olds from subsidized Hong Kong Government primary schools was completed in December 2006. Schools were randomly assigned to one of three groups: Control (CG); Educational program (EG); No-educational program (NEG).

INTERVENTION

In a short-term school-based intervention, heart-rate feedback was given either in combination with an educational program (EG) or in isolation (NEG). Long-term retention was assessed in comparison to the control group after 6 months follow-up.

MAIN OUTCOME MEASURES

Physical activity and changes in attraction to PA.

RESULTS

In the short-term, heart-rate monitor feedback increased total daily PA by an average of 24% (p<0.001) and vigorous PA by 0.6% (p<0.05). No change was found for moderate PA. Increases occurred regardless of involvement in the educational program, and in the absence of any change in attitudes towards PA. No long-term retention was apparent.

CONCLUSIONS

The findings from the study suggest that feedback from heart-rate monitors encourages low intensity PA, but when removed increases do not persist.

Physical activity, sedentary behaviour and energy balance in the preschool child: opportunities for early obesity prevention

Prevalence of obesity in preschool children has increased dramatically in recent years. The preschool years (age 3–6 years) have been regarded as critical for the programming of energy balance, via the concept of early ‘adiposity rebound’. Children who undergo early adiposity rebound are at increased risk of later obesity. Recent evidence suggests that associations between timing of adiposity rebound and later obesity may not reflect programming, but might denote that ‘obesogenic’ growth trajectories are often established by the preschool period. Studies of objectively-measured physical activity and sedentary behaviour in preschool children show that levels of physical activity are typically low and sedentary behaviour high. The review of evidence presented here is supportive of the hypothesis that physical activity is protective against obesity in the preschool period, and that sedentary behaviour, particularly television viewing, is obesogenic. Definitive evidence on dose–response relationships between physical activity, sedentary behaviour and obesity remain unclear. Dose–response evidence could be obtained fairly readily by intervention and longitudinal observational studies that use accelerometry in preschool children. The generalisability of much of the evidence base is limited and there is a need for research on the influence of physical activity and sedentary behaviour in the preschool years in the aetiology of obesity in the developing world.

Reduced cardiorespiratory fitness, low physical activity and an urban environment are independently associated with increased cardiovascular risk in children

AIMS/HYPOTHESIS

To assist in the development of preventive strategies, we studied whether the neighbourhood environment or modifiable behavioural parameters, including cardiorespiratory fitness (CRF) and physical activity (PA), are independently associated with obesity and metabolic risk markers in children.

METHODS

We carried out a cross-sectional analysis of 502 randomly selected first and fifth grade urban and rural Swiss schoolchildren with regard to CRF, PA and the neighbourhood (rural vs urban) environment. Outcome measures included BMI, sum of four skinfold thicknesses, homeostasis model assessment of insulin resistance (HOMA-IR) and a standardised clustered metabolic risk score.

RESULTS

CRF and PA (especially total PA, but also the time spent engaged in light and in moderate and vigorous intensity PA) were inversely associated with measures of obesity, HOMA-IR and the metabolic risk score, independently of each other, and of sociodemographic and nutritional parameters, media use, sleep duration, BMI and the neighbourhood environment (all p < 0.05). Children living in a rural environment were more physically active and had higher CRF values and reduced HOMA-IR and metabolic risk scores compared with children living in an urban environment (all p < 0.05). These differences in cardiovascular risk factors persisted after adjustment for CRF, total PA and BMI.

CONCLUSIONS/INTERPRETATION

Reduced CRF, low PA and an urban environment are independently associated with an increase in metabolic risk markers in children.

Motor skill performance and physical activity in preschool children

Children with better-developed motor skills may find it easier to be active and engage in more physical activity (PA) than those with less-developed motor skills. The purpose of this study was to examine the relationship between motor skill performance and PA in preschool children. Participants were 80 three- and 118 four-year-old children. The Children's Activity and Movement in Preschool Study (CHAMPS) Motor Skill Protocol was used to assess process characteristics of six locomotor and six object control skills; scores were categorized as locomotor, object control, and total. The actigraph accelerometer was used to measure PA; data were expressed as percent of time spent in sedentary, light, moderate-to-vigorous PA (MVPA), and vigorous PA (VPA). Children in the highest tertile for total score spent significantly more time in MVPA (13.4% vs. 12.8% vs. 11.4%) and VPA (5% vs. 4.6% vs. 3.8%) than children in middle and lowest tertiles. Children in the highest tertile of locomotor scores spent significantly less time in sedentary activity than children in other tertiles and significantly more time in MVPA (13.4% vs. 11.6%) and VPA (4.9% vs. 3.8%) than children in the lowest tertile. There were no differences among tertiles for object control scores. Children with poorer motor skill performance were less active than children with better-developed motor skills. This relationship between motor skill performance and PA could be important to the health of children, particularly in obesity prevention. Clinicians should work with parents to monitor motor skills and to encourage children to engage in activities that promote motor skill performance.

Preschool children and physical activity: a review of correlates

BACKGROUND

Several reviews have summarized the research on correlates of older children's and adolescents' physical activity behaviors, but none have been published on preschool children. Over the past 27 years, a number of studies have investigated the correlates of preschool children's physical activity behaviors. It is timely and necessary to review the extant literature in this area. This paper reviews articles investigating correlates of preschool children's physical activity behaviors published in peer-reviewed journals between 1980 and March 2007.

METHODS

A literature search was conducted to identify studies that investigated correlates of preschool children's physical activity. Data were collected and analyzed in 2007.

RESULTS

Twenty-four articles were identified that met the inclusion criteria. From those articles, 39 variables were identified across five domains. Results showed that boys were more active than girls, that children with active parents tended to be more active, and that children who spent more time outdoors were more active than children who spent less time outdoors. Age and BMI were consistently shown to have no association with preschool children's physical activity. Other variables produced largely inconclusive results.

CONCLUSIONS

The influences on the physical activity behaviors of preschool children are multidimensional. Further research is required to enhance an understanding of these influences.

Physical activity in preschoolers: understanding prevalence and measurement issues

Accurate physical activity quantification in preschoolers is essential to establish physical activity prevalence, dose-response relationships between activity and health outcomes, and intervention effectiveness. To date, best practice approaches for physical activity measurement in preschool-aged children have been relatively understudied. This article provides a review of physical activity measurement tools for preschoolers, an overview of measurement of preschoolers' physical activity, and directions for further research. Electronic and manual literature searches were used to identify 49 studies that measured young children's physical activity, and 32 studies that assessed the validity and/or reliability of physical activity measures with preschool-aged children. While no prevalence data exist, measurement studies indicate that preschool children exhibit low levels of vigorous activity and high levels of inactivity, boys are more active than girls, and activity patterns tend to be sporadic and omnidirectional. As such, measures capable of capturing differing activity intensities in very short timeframes and over multiple planes are likely to have the most utility with this population. Accelerometers are well suited for this purpose, and a number of models have been used to objectively quantify preschoolers' physical activity. Only one model of pedometer has been investigated for validity with preschool-aged children, showing equivocal results. Direct observation of physical activity can provide detailed contextual information on preschoolers' physical activity, but is subjective and impractical for understanding daily physical activity. Proxy-report questionnaires are unlikely to be useful for determining actual physical activity levels of young children, and instead may be useful for identifying potential correlates of activity. Establishing validity is challenging due to the absence of a precise physical activity measure, or 'criterion', for young children. Both energy expenditure (EE) and direct observation have been considered criterion measures in the literature; however, EE is influenced by multiple variables, so its use as a physical activity 'criterion' is not ideal. Also, direct observation is inherently subjective, and coding protocols may result in failure to capture intermittent activity, thereby limiting its utility as a physical activity criterion. Accordingly, these issues must be taken into account where EE or direct observation are used to validate physical activity instruments. A combination of objective monitoring and direct observation may provide the best standard for the assessment of physical activity measurement tools. Ideally, the convergent validity of various physical activity tools should be investigated to determine the level of agreement between currently available measures. The correlational approaches commonly employed in the assessment of physical activity measures do not reveal this relationship, and can conceal potential bias of either measure.

Energy balance and its measurement in childhood disease

Under and overweight, usually secondary to energy imbalance, are common complications of childhood chronic disease. A simple energy balance paradigm has been helpful in understanding the etiology of underweight and overweight in chronic disease, including malignant disease, particularly when measurements of total energy expenditure have been made using the doubly labeled water method. Measurements of energy intake are usually insufficiently accurate and precise to be informative, and measurements of energy expended at rest alone provide an incomplete and potentially misleading assessment of energy expenditure and the causes of energy imbalance. In some diseases, such as acute lymphoblastic leukemia, the natural history and etiology of energy imbalance are now particularly well understood. Recent improvements in our understanding of etiology should lead to improved strategies for the prevention and treatment of underweight and overweight in chronic disease. In some diseases, cachectic processes drive the development of underweight: these are partly independent of energy balance, and strategies for prevention and treatment may require approaches aimed at modifying the cachectic process rather than attempting to modify energy balance directly.

Ethnic differences in overweight and obesity in early adolescence in the MRC DASH study: the role of adolescent and parental lifestyle

BACKGROUND

Ethnicity is a consistent correlate of excess weight in youth. We examine the influence of lifestyles on ethnic differences in excess weight in early adolescence in the UK.

METHOD

Data were collected from 6599 pupils, aged 11-13 years in 51 schools, on dietary practices and physical activity, parental smoking and overweight, and on overweight and obesity (using International Obesity Task Force criteria).

RESULTS

Skipping breakfast [girls odds ratio (OR) 1.74, 95% confidence interval (CI) 1.30-2.34; boys OR 2.06; CI 1.57-2.70], maternal smoking (girls OR 2.04, CI 1.49-2.79; boys OR 1.63, CI 1.21-2.21) and maternal overweight (girls OR 2.01, CI 1.29-3.13; boys OR 2.47, CI 1.63-3.73) were associated with obesity. Skipping breakfast, more common among girls, was associated with other poor dietary practices. Compared with White UK peers, Black Caribbeans (girls OR 1.62, CI 1.24-2.12; boys OR 1.49, CI 1.15-1.95) and Black Africans (girls OR 1.96, CI 1.52-2.53; boys OR 2.50, CI 1.92-3.27) were more likely to skip breakfast and engage in other poor dietary practices, and Indians were least likely. White Other boys reported more maternal smoking (OR 1.37, CI 1.03-1.82). All these reports were more common among those born in the UK than those born elsewhere. Black Caribbean girls were more likely to be overweight (OR 1.38, CI 1.02-1.87) and obese (OR 1.65, CI 1.05-2.58), Black African girls to be overweight (OR 1.35, CI 1.02-1.79) and White Other boys to be overweight (OR 1.37, CI 1.00-1.88) and obese (OR 1.86, CI 1.15-3.00). Adverse dietary habits and being born in the UK contributed to these patterns.

CONCLUSION

These findings signal a potential exacerbating effect on ethnic differences in obesity if adverse dietary habits persist. Combined adolescent and parent-focused interventions should be considered.

Comparison of equations for predicting energy expenditure from accelerometer counts in children

Several prediction equations developed to convert body movement measured by accelerometry into energy expenditure have been published. The aim of this study was to examine the degree of agreement between three different prediction equations, when applied to data on physical activity in a large sample of children. We examined 1321 children (663 boys, 658 girls; mean age 9.6+/-0.4 years) from four different countries. Physical activity was measured by the MTI accelerometer. One equation, derived from doubly labeled water (DLW) measurements, was compared with one treadmill-based (TM) and one room calorimeter-based (CAL) equation (mixture of activities). Predicted physical activity energy expenditure (PAEE) was the main outcome variable. In comparison with DLW-predicted PAEE, both laboratory-derived equations significantly (P<0.001) overestimated PAEE by 17% and 83%, respectively, when based on a 24-h prediction, while the TM equation significantly (P<0.001) underestimated PAEE by 46%, when based on awake time only. In contrast, the CAL equation agreed better with the DLW equation under the awake time assumption. Predicted PAEE differ substantially between equations, depending on time-frame assumptions, and interpretations of average levels of PAEE in children from available equations should be made with caution. Further development of equations applicable to free-living scenarios is needed.

Physical activity assessment with accelerometers: an evaluation against doubly labeled water

This review focuses on the ability of different accelerometers to assess daily physical activity as compared with the doubly labeled water (DLW) technique, which is considered the gold standard for measuring energy expenditure under free-living conditions. The PubMed Central database (U.S. NIH free digital archive of biomedical and life sciences journal literature) was searched using the following key words: doubly or double labeled or labeled water in combination with accelerometer, accelerometry, motion sensor, or activity monitor. In total, 41 articles were identified, and screening the articles' references resulted in one extra article. Of these, 28 contained sufficient and new data. Eight different accelerometers were identified: 3 uniaxial (the Lifecorder, the Caltrac, and the CSA/MTI/Actigraph), one biaxial (the Actiwatch AW16), 2 triaxial (the Tritrac-R3D and the Tracmor), one device based on two position sensors and two motion sensors (ActiReg), and the foot-ground contact pedometer. Many studies showed poor results. Only a few mentioned partial correlations for accelerometer counts or the increase in R(2) caused by the accelerometer. The correlation between the two methods was often driven by subject characteristics such as body weight. In addition, standard errors or limits of agreement were often large or not presented. The CSA/MTI/Actigraph and the Tracmor were the two most extensively validated accelerometers. The best results were found for the Tracmor; however, this accelerometer is not yet commercially available. Of those commercially available, only the CSA/MTI/Actigraph has been proven to correlate reasonably with DLW-derived energy expenditure.

Accelerometers and pedometers: methodology and clinical application

PURPOSE OF REVIEW

The relationship between physical activity and health varies considerably, partly due to the difficulty of assessing physical activity accurately. This review examines recent literature on the validation of movement sensors to assess habitual physical activity. Recommendations are given for the use of movement sensors during free-living conditions and methods of data analysis and interpretation are discussed.

RECENT FINDINGS

Recent progress in physical-activity research includes detailed comparative studies of different monitor brands. The move away from using linear-regression equations and the use of novel data-analysis strategies is increasing the accuracy with which energy expenditure can be estimated from accelerometry. New technologies, including the combination of accelerometry with the measurement of physiological parameters, have great potential for the increased accuracy of physical-activity assessment.

SUMMARY

Accelerometry is able to adequately assess physical activity and its association with health outcomes but currently methods have limited accuracy for the estimation of free-living energy expenditure. Pedometers provide an inexpensive overall measure of physical activity but are unable to assess intensity, frequency and duration of activity or to estimate energy expenditure. Interpretation of monitor output is best kept as close to the measurement domain as possible.

Predictive validity of an age-specific MET equation among youth of varying body size

The purpose of this study was to cross-validate the age-specific Freedson MET equation among children and adolescents of varying body size. Sixty-seven children (41 boys; 26 girls) between 6 and 13 years completed five 3-min trials (1.6, 3.2, 4.0, 4.8, and 6.4 km h(-1)) on a motorized treadmill. During each trial, participants wore an Actigraph accelerometer while oxygen consumption was assessed by indirect calorimetry. Using the Actigraph activity counts, predicted MET values were determined with the age-specific Freedson equation and were compared with measured MET values using dependent t tests. Participants were divided into body size categories based on their calculated body surface area (BSA, m2) (small: BSA<or=0.96 m2; medium: 0.96 m2<BSA<or=1.20 m2; large: BSA>1.20 m2) to determine if body size influenced the difference between measured and predicted MET values. The measured MET value was similar to the predicted MET value at the slowest treadmill speed (1.6 km h(-1)) (2.3 vs. 2.3 METs); however, the measured MET value was lower than the predicted MET value at the remaining speeds (3.2, 4.0, 4.8, and 6.4 km h(-1)) (P<0.001). With the exception of the fastest treadmill speed (6.4 km h(-1)), the mean difference between the measured and predicted MET values was greater between the two smaller BSA categories compared to the largest BSA category. The results suggest that the age-specific Freedson child equation significantly overestimates energy expenditure (METs) during locomotor speeds between 3.2 and 6.4 km h(-1). This effect was primary observed among relatively smaller children.

The association between an objective measure of physical activity and weight status in preschoolers

OBJECTIVE

Our objective was to determine the association between physical activity and BMI among racially diverse low-income preschoolers.

RESEARCH METHODS AND PROCEDURES

This was a cross-sectional study of 2- to 5-year-olds (n = 56) enrolled in Massachusetts Special Supplemental Nutrition Program for Women, Infants & Children (WIC). Physical activity was measured for 7 consecutive days with an accelerometer. Height and weight were obtained from WIC records, and BMI-for-age percentiles were calculated based on the Centers for Disease Control and Prevention's (CDC) 2000 Growth Charts. At-risk-for-overweight (BMI-for-age of > or = 85th to < 95th percentile) and overweight (BMI-for-age > or = 95th percentile) groups were combined and referred to as overweight. Final analysis inclusion criteria were: completion of 4.5 days of activity assessment and anthropometric data obtained within 90 and 120 days of the activity assessment for children ages 24 to 35.99 and 36 to 59.99 months, respectively.

RESULTS

Overweight children had significantly lower mean daily very vigorous minutes (VVM) (2.6 mins vs. 4.6 mins, p < 0.05) and lower very active minutes (VAM) [i.e., sum of vigorous minutes (VM) and VVM] per day (22.9 mins vs. 32.1 mins, p < 0.05) than children who were not overweight. Daily VVM [odds ratio (OR) = 0.68; 95% confidence interval (CI), 0.49 to 0.96], VM (OR = 0.94; CI, 0.88 to 1.00), and VAM (OR = 0.94; 95% CI, 0.89 to 1.00) were all associated with significantly lower odds of being overweight.

DISCUSSION

This study suggests that, in a diverse group of preschoolers, vigorous and very vigorous activity are associated with lower odds of overweight. However, these findings require corroboration in a diverse sample of preschoolers using a longitudinal design.

Parental feeding style, energy intake and weight status in young Scottish children

Parental feeding style, as measured by the Child Feeding Questionnaire (CFQ), may be an important influence on child feeding behaviour and weight status in early to mid childhood, but more evidence on parental feeding style is required from samples outside the USA. We aimed to use the CFQ in a sample of 117 Scottish children (boys n 53, girls n 64 mean age 4.6 (SD 0.5) years) to: characterise gender differences and changes over time (in forty of the 117 children studied over 2 years); test associations between parental feeding style, free-living energy intake (measured over 3 days using the multiple pass 24-h recall), and weight status (BMI SD score). No dimensions of parental feeding style changed significantly over 2 years in the longitudinal study (P>0.05 in all cases). No aspects of parental feeding style as measured by the CFQ differed significantly between the sexes (P>0.05 in all cases). Parental perceptions of child weight status were generally significantly positively correlated with child weight status as measured by the BMI SD score. In this sample and setting, measures of parental control over child feeding were generally not associated with child energy intake or weight status.

Body mass index has risen more steeply in tall than in short 3-year olds: serial cross-sectional surveys 1988–2003

OBJECTIVE

To monitor the changing relationship between body mass index (BMI) and height in young children.

DESIGN

Annual cross-sectional surveys using health-visitor-collected routine data 1988-2003.

SETTING

Wirral, England.

PARTICIPANTS

Fifty thousand four hundred and fifty-five children (49% female) each measured once at the age of 3 years.

MAIN OUTCOME MEASURES

Weight, height and derived BMI (weight/height(2)) adjusted for age and sex (British 1990 revised reference) using standard deviation scores.

RESULTS

From 1988 to 2003, mean BMI increased by 0.7 kg/m(2), whereas mean height fell by 0.5 cm. Over the same period, the weight-height correlation rose from 0.59 to 0.71 (P<0.0001) owing to BMI increasing faster in the taller than the shorter children. Among the shortest 10% of children, mean BMI rose by 0.12 (95% confidence interval: -0.05-0.28) kg/m(2) as against 1.38 (1.19-1.56) kg/m(2) among the tallest 10%, a 12-fold difference. Adjustment for age, sex, seasonality, birth-weight and deprivation did not alter the findings.

CONCLUSIONS

Among 3-year-old children in Wirral, where BMI has been rising for 16 years, the largest increase in BMI has occurred in the tallest children, whereas in the shortest BMI has hardly changed. Tall stature has, therefore, become important for child obesity. It suggests a drive to increasing adiposity in young children that involves both growth and appetite, with fast growing and hungrier children now more exposed to the 'obesogenic' environment.

Improving the specificity of the [13C]mixed triacylglycerol breath test by estimating carbon dioxide production from heart rate

BACKGROUND

The [13C]mixed triacylglycerol (MTG) breath test is a non-invasive measure of fat digestion and can be used to assess the need for enzyme replacement therapy in children with cystic fibrosis (CF). However, it lacks specificity. Quantitation of cumulative percent dose recovered (cPDR) requires knowledge of carbon dioxide production rate (VCO2). A resting value is assumed, but children are unlikely to remain at rest during the test.

OBJECTIVE

To improve the specificity and therefore the positive predictive value (PPV) of the MTG breath test using calibrated heart rate monitors to estimate non-resting VCO2.

DESIGN

Proof of concept study.

SUBJECTS

Six children with CF, 10 healthy children and eight healthy adults performed [13C]MTG breath tests.

METHODS

Heart rate monitors were worn throughout the test. Non-resting VCO2 was estimated continuously from heart rate. Percentage dose recovered was calculated using predicted resting VCO2, measured resting VCO2 and non-resting VCO2 estimated from heart rate. Physical activity level (PAL) was taken as cPDR calculated using non-resting VCO2 divided by cPDR calculated using measured resting VCO2. The cutoff point was determined using two graph-receiver operator characteristics.

RESULTS

Use of calibrated heart rate monitors to estimate non-resting VCO2 improved the specificity of the test. The PPV increased from 0.67 to 0.99. PAL was 1.3 in adults and children who performed the test in hospital, and 1.7 in children who performed the test at home.

CONCLUSION

Individually calibrated heart rate monitors are useful tools to estimate non-resting VCO2 during the [13C]MTG breath test.

Childhood obesity: a growing public health concern

Childhood obesity has been deemed epidemic, a term usually reserved for infectious diseases that sweep populations. This review begins with guidance regarding obesity definitions and a review of the data on global prevalence. The next section details the myriad health consequences for immediate and long-term physical and psychosocial health outcomes. The authors then discuss what is known regarding distal and proximal causes and correlates at the individual and contextual levels of family, health care, schools and community. The final sections provide a summary of interventions in diverse settings and some current thinking on how the field is likely to evolve over the next several years.

Nonalcoholic fatty liver disease in children

Nonalcoholic fatty liver disease (NAFLD) is likely to reach epidemic proportions in children worldwide in the next decade. NAFLD may be the hepatic aspect of the metabolic syndrome in adults and children. The entire range of liver involvement characterizing NAFLD can occur in children: hepatic macrovesicular steatosis without inflammation, steatosis with inflammation or fibrosis, and cirrhosis. NAFLD may be more severe in children from certain ethnic groups or in association with metabolic disorders characterized by abnormalities in insulin receptor structure and function. Treatment strategies focus on modifying risk factors because specific drug treatments are lacking. Overweight/obesity should be identified as early as possible. Comprehensive clinical management to normalize weight should be instituted immediately to avoid hepatic and nonhepatic complications.

Effect of socioeconomic status on objectively measured physical activity

BACKGROUND

A socioeconomic gradient in childhood obesity is known to be present by the age of school entry in the UK. The origin of this gradient is unclear at present, but must lie in socioeconomic differences in habitual physical activity, sedentary behaviour, or dietary intake.

AIMS

To test the hypothesis that habitual physical activity and/or sedentary behaviour are associated with socioeconomic status (SES) in young Scottish children.

METHODS

Observational study of 339 children (mean age 4.2 years, SD 0.3) in which habitual physical activity and sedentary behaviour were measured by accelerometry over six days (study 1). In a second study, 39 pairs of children of distinctly different SES (mean age 5.6 years, SD 0.3) were tested for differences in habitual physical activity and sedentary behaviour by accelerometry over seven days.

RESULTS

In study 1, SES was not a significant factor in explaining the amount of time spent in physical activity or sedentary behaviour once gender and month of measurement were taken into account. In study 2, there were no significant differences in time spent in physical activity or sedentary behaviour between affluent and deprived groups.

CONCLUSION

Results do not support the hypothesis that low SES in young Scottish children is associated with lower habitual physical activity or higher engagement in sedentary behaviour.

Validation of energy intake by 24-hour multiple pass recall: comparison with total energy expenditure in children aged 5-7 years

Accurate measurement of energy intake (EI) is essential in studies of energy balance in all age groups. Reported values for EI can be validated against total energy expenditure (TEE) measured using doubly labelled water (DLW). Our previous work has indicated that the use of the standardized 24 h multiple pass recall (24 h MPR) method produces slight overestimates of EI in pre-school children which are inaccurate at individual level but acceptable at group level. To extend this work, the current study validated EI by 24 h MPR against TEE by DLW in sixty-three (thirty-two boys) school-aged children (median age 6 years). In both boys and girls, reported EI was higher than TEE, although this difference was only significant in the girls (median difference 420 kJ/d, P=0.05). On analysis of agreement between TEE and EI, the group bias was an overestimation of EI by 250 kJ/d with wide limits of agreement (-2880, 2380 kJ/d). EI was over-reported relative to TEE by 7 % and 0.9 % in girls and boys, respectively. The bias in the current study was lower than in our previous study of pre-school children, suggesting that estimates of EI become less inaccurate as children age. However, the current study suggests that the 24 h MPR is inaccurate at the individual level.

Comparison of accuracy and precision of heart rate calibration methods to estimate total carbon dioxide production during 13C-breath tests

BACKGROUND

13C-breath tests are noninvasive tools to measure gastrointestinal function and nutritional interventions. Calculation of percentage dose recovered of 13C in exhaled breath requires knowledge of CO2 production rate (VC02). A resting value is usually assumed, but this can underestimate VC02 because subjects are unlikely to remain at rest during tests that last for many hours. There is a need for a method to estimate nonresting VC02 during 13C-breath tests.

OBJECTIVE

To calibrate a heart rate monitor to continually estimate VC02 during 13C-breath tests.

DESIGN

Proof of concept study.

SUBJECTS

Eight healthy adults, 10 healthy children and six children with cystic fibrosis.

METHODS

Heart rate and VC02 were measured simultaneously at resting and nonresting levels. A new calibration method (smoothing heart rate and fitting a sigmoid function) was compared with published methods. A [ 3C]acetate breath test was used to demonstrate the range of physical activity during breath tests.

RESULTS

The new calibration method was more accurate than existing methods (mean bias -0.0002%, 95% confidence interval (CI) -0.0007, 0.0003% of the mean measured VC02). Smoothing heart rate gave a more precise estimate of VC02 and a more accurate estimate of resting energy expenditure (mean bias -0.09, 95% Cl -0.22, 0.05 mmol CO2 min-' m-2 body surface area) than using raw data (mean bias -0.21, 95% Cl -0.38, -0.04 mmol CO2 min' m-2 body surface area). Physical activity level ranged from 1.0 to 2.5 in children, and 1.0 to 1.5 in adults.

CONCLUSION

Use of smoothed HR with a sigmoid function provides an accurate method of estimating nonresting VC02 during 13C-breath tests.

Physical activity patterns in nonobese and obese children assessed using minute-by-minute accelerometry

OBJECTIVE

To determine the levels and patterns of physical activity in a sample of obese (> or =99th percentile body mass index (BMI)) and nonobese (<99th percentile BMI) children.

DESIGN

Cross-sectional study.

SETTING

Children were recruited from schools in Bristol and from the childhood obesity clinic, Bristol Royal Hospital for Children. Children were instructed in the use of the accelerometer either while at school or in the clinic, and wore the instrument while carrying out their normal daily activities for 7 days.

PARTICIPANTS

A total of 133 children (mean age 10.5+/-0.8 y). In all 11 (16.9%) of the 65 girls and 14 (20.6%) of the 68 boys were classified as obese (above the 99th percentile for BMI and corresponding to projected adult BMI of 30).

MAIN OUTCOME MEASURES

Objectively measured physical activity volume, intensity and pattern.

RESULTS

Obese children were significantly less physically active overall than their nonobese counterparts (31,844+/-13,200 vs 41,844+/-10,430 counts/h; 95% confidence interval 4407 to 15592; P=0.001). Similarly the obese children spent less time in physical activity of moderate or greater intensity than the nonobese children (9.9+/-3.9 vs 12.9+/-4.2 min/h; 95% confidence interval 1.15 to 4.80; P=0.002). Hourly patterns of activity indicated a tendency in obese children to be less active than nonobese children at times when activity was more likely to be determined by free choice, particularly outside of school time.

CONCLUSIONS

Obese children demonstrated patterns of physical activity that may have contributed to and are likely to sustain their obesity. Minute-by-minute accelerometry is a valuable tool to investigate physical activity patterns in obese children. It can identify periods when intervention to increase activity may be most appropriate and provide an evidence base for specific exercise prescription in primary and secondary care.