Energy expenditure and physical fitness in overweight vs non-overweight prepubertal girls

Prediction Equation for Physical Activity Energy Expenditure in 11-13-Year-Old Sri Lankan Children

This study aimed to develop a regression equation to predict physical activity energy expenditure (PAEE) using accelerometry. Children aged 11-13 years were recruited and randomly assigned to validation (n = 54) and cross-validation (n = 25) groups. The doubly labelled water (DLW) technique was used to assess energy expenditure and accelerometers were worn by participants across the same period. A preliminary equation was developed using stepwise multiple regression analysis with sex, height, weight, body mass index, fat-free mass, fat mass and counts per minute (CPM) as independent variables. Goodness-of-fit statistics were used to select the best prediction variables. The PRESS (predicted residual error sum of squares) statistical method was used to validate the final prediction equation. The preliminary equation was cross-validated on an independent group and no significant (p > 0.05) difference was observed in the PAEE estimated from the two methods. Independent variables of the final prediction equation (PAEE = [0.001CPM] - 0.112) accounted for 70.6% of the variance. The new equation developed to predict PAEE from accelerometry was found to be valid for use in Sri Lankan children.

Resting Energy Expenditure and Body Composition in Children and Adolescents With Genetic, Hypothalamic, Medication-Induced or Multifactorial Severe Obesity

BACKGROUND

Pediatric obesity is a multifactorial disease which can be caused by underlying medical disorders arising from disruptions in the hypothalamic leptin-melanocortin pathway, which regulates satiety and energy expenditure.

AIM

To investigate and compare resting energy expenditure (REE) and body composition characteristics of children and adolescents with severe obesity with or without underlying medical causes.

METHODS

This prospective observational study included pediatric patients who underwent an extensive diagnostic workup in our academic centre that evaluated endocrine, non-syndromic and syndromic genetic, hypothalamic, and medication-induced causes of obesity. REE was assessed by indirect calorimetry; body composition by air displacement plethysmography. The ratio between measured REE (mREE) and predicted REE (Schofield equations), REE%, was calculated, with decreased mREE defined as REE% ≤90% and elevated mREE ≥110%. Additionally, the influence of fat-free-mass (FFM) on mREE was evaluated using multiple linear regression.

RESULTS

We included 292 patients (146 [50%] with body composition measurements), of which 218 (75%) patients had multifactorial obesity and 74 (25%) an underlying medical cause: non-syndromic and syndromic genetic (n= 29 and 28, respectively), hypothalamic (n= 10), and medication-induced (n= 7) obesity. Mean age was 10.8 ± 4.3 years, 59% were female, mean BMI SDS was 3.8 ± 1.1, indicating severe obesity. Mean REE% was higher in children with non-syndromic genetic obesity (107.4% ± 12.7) and lower in children with hypothalamic obesity (87.6% ± 14.2) compared to multifactorial obesity (100.5% ± 12.6, both p<0.01). In 9 children with pseudohypoparathyroidism type 1a, mean REE% was similar (100.4 ± 5.1). Across all patients, mREE was decreased in 60 (21%) patients and elevated in 69 (24%) patients. After adjustment for FFM, mREE did not differ between patients within each of the subgroups of underlying medical causes compared to multifactorial obesity (all p>0.05).

CONCLUSIONS

In this cohort of children with severe obesity due to various etiologies, large inter-individual differences in mREE were found. Consistent with previous studies, almost half of patients had decreased or elevated mREE. This knowledge is important for patient-tailored treatment, e.g. personalized dietary and physical activity interventions and consideration of pharmacotherapy affecting central energy expenditure regulation in children with decreased mREE.

Resting Energy Expenditure Is Not Altered in Children and Adolescents with Obesity. Effect of Age and Gender and Association with Serum Leptin Levels

In children and adolescents, obesity does not seem to depend on a reduction of resting energy expenditure (REE). Moreover, in this young population, the interactions between either age and obesity or between age and gender, or the role of leptin on REE are not clearly understood. To compare the levels of REE in children and adolescents we studied 181 Caucasian individuals (62% girls) classified on the basis of age- and sex-specific body mass index (BMI) percentile as healthy weight (n = 50), with overweight (n = 34), or with obesity (n = 97) and in different age groups: 8–10 (n = 38), 11–13 (n = 50), and 14–17 years (n = 93). REE was measured by indirect calorimetry and body composition by air displacement plethysmography. Statistically significant differences in REE/fat-free mass (FFM) regarding obesity or gender were not observed. Absolute REE increases with age (p < 0.001), but REE/FFM decreases (p < 0.001) and there is an interaction between gender and age (p < 0.001) on absolute REE showing that the age-related increase is more marked in boys than in girls, in line with a higher FFM. Interestingly, the effect of obesity on absolute REE is not observed in the 8–10 year-old group, in which serum leptin concentrations correlate with the REE/FFM (r = 0.48; p = 0.011). In conclusion, REE/FFM is not affected by obesity or gender, while the effect of age on absolute REE is gender-dependent and leptin may influence the REE/FFM in 8–10 year-olds.

Effects of obesity on the oxygen cost of breathing in children

The objective of this study was to examine the effects of obesity on the oxygen (O₂) cost of breathing using the eucapnic voluntary hyperpnea (EVH) technique in 10- and 11-year-old children. Seventeen children (8 without and 9 with obesity) underwent EVH trials at two levels of ventilation for assessing the O₂ cost of breathing (slope of oxygen uptake, V˙O₂ vs. minute ventilation) and a dual energy x-ray absorptiometry scan. Resting and EVH V˙O₂ was higher in children with obesity when compared with children without obesity (P = 0.0096). The O₂ cost of breathing did not statistically differ between children without (2.09 ± 0.46 mL/L) and with obesity (2.08 ± 0.64 mL/L, P = 0.99), but the intercept was significantly greater in children with obesity. Chest mass explained 85 % of the variance in resting V˙O₂ in children with obesity. Higher resting energy requirements, attributable to increased chest mass, can increase the absolute metabolic costs of exercise and hyperpnea in children with obesity.

Constraint and trade-offs regulate energy expenditure during childhood

Children's metabolic energy expenditure is central to evolutionary and epidemiological frameworks for understanding variation in human phenotype and health. Nonetheless, the impact of a physically active lifestyle and heavy burden of infectious disease on child metabolism remains unclear. Using energetic, activity, and biomarker measures, we show that Shuar forager-horticulturalist children of Amazonian Ecuador are ~25% more physically active and, in association with immune activity, have ~20% greater resting energy expenditure than children from industrial populations. Despite these differences, Shuar children's total daily energy expenditure, measured using doubly labeled water, is indistinguishable from industrialized counterparts. Trade-offs in energy allocation between competing physiological tasks, within a constrained energy budget, appear to shape childhood phenotypic variation (e.g., patterns of growth). These trade-offs may contribute to the lifetime obesity and metabolic health disparities that emerge during rapid economic development.

Total Energy Expenditure by the Doubly-Labeled Water Method in Rural Preschool Children in Cuba

An evaluation of the capacity of the Cuban Nutrition Program for covering the energy requirements of children was carried out in children 5.0 ± 1.0 years of age in a rural mountain community in Cuba. Five males and six females (19 ± 3.05 kg average weight) with a mean BMI 15.4 ± 2.2 kg/m2) were included in the study. Six of the subjects were well-nourished, three were undernourished, and two were overweight. Total energy expenditure was determined by the doubly-labeled water technique. Resting metabolic rate was measured by indirect calorimetry. Energy intake, measured by a three-day weighed dietary record, was 1,527 kcal/day (6.39 MJ). The total energy expenditure of the well-nourished children was 11.8% lower than present energy recommendations (1,773 kcal). This implies that well-nourished children who are moderately to heavily physically active require 82.6 kcal/kg per day. The physical activity level of normal Cuban children is nearly 1.8, which is much higher than that reported in studies of children from industrialized countries using the doubly-labeled water technique. The measured daily energy intake was 1.7 times the resting metabolic rate RMR and 1.04 times the total energy expenditure.

Comparison of daily physical activity parameters using objective methods between overweight and normal-weight children

PURPOSE

The purpose of the present study was to determine if there were any differences in various aspects of physical activity such as energy expenditure, intensity, and type of activity between normal-weight and overweight boys.

METHODS

Children aged 9-12 years were recruited from 2 elementary schools located in different urban districts in Republic of Korea. The present study included 45 Korean boys, of which 19 were normal-weight and 26 were overweight. Daily physical activity was estimated over the same 1-week study period under free-living conditions using the doubly labeled water (DLW) method and a tri-axial accelerometer. Resting metabolic rate (RMR) was measured using the Douglas bag method and open-circuit indirect calorimetry. We calculated the physical activity level (PAL) as the total energy expenditure (TEE)/RMR.

RESULTS

PAL was not significantly different between the groups. In the accelerometer data, time spent in locomotive moderate-to-vigorous physical activity (MVPA) was significantly lower in overweight boys than in normal-weight subjects, whereas other variables including non-locomotive activity did not differ between groups. In addition, among all participants, time spent in total locomotive activity was significantly associated with PAL. Time spent in locomotive MVPA was significantly associated with PAL.

CONCLUSION

Overweight boys may be less physically active based on locomotive MVPA, which was positively related with PAL. Our findings suggest that the contribution of locomotive MVPA to the increase in PAL was relatively significant.

Pain Response after Maximal Aerobic Exercise in Adolescents across Weight Status

INTRODUCTION

Pain reports are greater with increasing weight status, and exercise can reduce pain perception. It is unknown, however, whether exercise can relieve pain in adolescents of varying weight status. The purpose of this study was to determine whether adolescents across weight status report pain relief after high-intensity aerobic exercise (exercise-induced hypoalgesia (EIH)).

METHODS

Sixty-two adolescents (15.1 ± 1.8 yr, 29 males) participated in the following three sessions: 1) pressure pain thresholds (PPT) before and after quiet rest, clinical pain (McGill Pain Questionnaire), and physical activity levels (self-report and ActiSleep Plus Monitors) were measured, 2) PPT were measured with a computerized algometer at the fourth finger's nailbed, middle deltoid muscle, and quadriceps muscle before and after maximal oxygen uptake test (V˙O2max Bruce Treadmill Protocol), and 3) body composition was measured with dual-energy x-ray absorptiometry.

RESULTS

All adolescents met criteria for V˙O2max. On the basis of body mass index z-score, adolescents were categorized as having normal weight (n = 33) or being overweight/obese (n = 29). PPT increased after exercise (EIH) and were unchanged with quiet rest (trial × session, P = 0.02). EIH was similar across the three sites and between normal-weight and overweight/obese adolescents. Physical activity and clinical pain were not correlated with EIH. Overweight/obese adolescents had similar absolute V˙O2max (L·min(-1)) but lower relative V˙O2max (mL·kg(-1)·min(-1)) compared with normal-weight adolescents. When adolescents were categorized using FitnessGram standards as unfit (n = 15) and fit (n = 46), the EIH response was similar between fitness levels.

CONCLUSIONS

This study is the first to establish that both overweight and normal-weight adolescents experience EIH. EIH after high-intensity aerobic exercise was robust in adolescents regardless of weight status and not influenced by physical fitness.

Regular physical activity has differential association with reduced obesity among diverse youth in the United States

This study examined whether daily or almost daily lower-intensity physical activity was associated with reduced obesity, among 4824 African American, Hispanic, and White youth assessed in fifth and seventh grades. Regular lower-intensity physical activity was associated with reduced obesity only among Hispanic and White males and only in seventh grade, and not among youth in fifth grade, females, or African American males or females. Findings from this study suggest that the reduced obesity risk generally attributed to physical activity may not be consistent across racial/ethnic and gender groups of early adolescents.

A Study of VO2 Max and Body Fat Percentage in Female Athletes

INTRODUCTION

Aerobic capacity of athletes is an important element of success in sports achievements. It is generally considered the best indicator of cardio respiratory endurance and athletic fitness. Body fat percentage affects VO2 max and thus the cardiovascular status of the athletes. The present study was undertaken to assess the VO2 max and body fat percentage in athletes. The secondary objective of the study was to study the relationship between VO2 max and body fat percentage.

MATERIALS AND METHODS

Twenty five female athletes of age group 17-22years were selected for the study. VO2 max was determined by Queen's college step test and body fat percentage by skin fold calipers. The VO2 max and body fat percentage were determined in non athletes of same age group for comparison. The statistical analysis was done by Student's t-test and Pearson correlation test.

OBSERVATION AND RESULTS

The mean VO2 max in athletic group was 39.62 ± 2.80 ml/kg/min. In non-athletic group, VO2 max was 23.54 ± 3.26 ml/kg/min. The mean body fat percentage in athletes was 24.11 ± 1.83% and in non-athletes it was 29.31 ± 3.86%.The difference in VO2 max and body fat percentage was statistically significant in our study. The VO2 max and body fat percentage in both the groups showed negative correlation by Pearson test but, was not statistically significant.

CONCLUSION

The present study showed a statistically significant higher VO2 max in female athletes. The study showed a negative correlation between VO2 max and body fat percentage but was not statistically significant.

A 6-year exercise program improves skeletal traits without affecting fracture risk: a prospective controlled study in 2621 children

Most pediatric exercise intervention studies that evaluate the effect on skeletal traits include volunteers and follow bone mass for less than 3 years. We present a population-based 6-year controlled exercise intervention study in children with bone structure and incident fractures as endpoints. Fractures were registered in 417 girls and 500 boys in the intervention group (3969 person-years) and 835 girls and 869 boys in the control group (8245 person-years), all aged 6 to 9 years at study start, during the 6-year study period. Children in the intervention group had 40 minutes daily school physical education (PE) and the control group 60 minutes per week. In a subcohort with 78 girls and 111 boys in the intervention group and 52 girls and 54 boys in the control group, bone mineral density (BMD; g/cm(2) ) and bone area (mm(2) ) were measured repeatedly by dual-energy X-ray absorptiometry (DXA). Peripheral quantitative computed tomography (pQCT) measured bone mass and bone structure at follow-up. There were 21.7 low and moderate energy-related fractures per 1000 person-years in the intervention group and 19.3 fractures in the control group, leading to a rate ratio (RR) of 1.12 (0.85, 1.46). Girls in the intervention group, compared with girls in the control group, had 0.009 g/cm(2) (0.003, 0.015) larger gain annually in spine BMD, 0.07 g (0.014, 0.123) larger gain in femoral neck bone mineral content (BMC), and 4.1 mm(2) (0.5, 7.8) larger gain in femoral neck area, and at follow-up 24.1 g (7.6, 40.6) higher tibial cortical BMC (g) and 23.9 mm(2) (5.27, 42.6) larger tibial cross-sectional area. Boys with daily PE had 0.006 g/cm(2) (0.002, 0.010) larger gain annually in spine BMD than control boys but at follow-up no higher pQCT values than boys in the control group. Daily PE for 6 years in at study start 6- to 9-year-olds improves bone mass and bone size in girls and bone mass in boys, without affecting the fracture risk.

Increased lipid oxidation during exercise in obese pubertal girls: a QUALITY study

OBJECTIVE

This study explores differences in LO rates between pre-pubertal and pubertal girls of three body weight status groups.

METHODS

The sample included 39 pre-pubertal girls [12 normal-weight (NW), 12 overweight (OW), and 15 obese (OB)] and 37 pubertal girls [16 NW, 10 OW, and 11 OB]. Following a rest period, the girls performed a graded maximal cycling test. The %LO contribution was computed at each stage.

RESULTS

The %LO contribution did not differ between NW, OW, or OB pre-pubertal girls at each exercise stage. In contrast, pubertal OB girls showed a statistically significantly higher %LO contribution at 25, 50, and 75 W stages compared with OW and NW as well as with OB pre-pubertal girls.

CONCLUSIONS

Our results demonstrate that entering puberty is a period associated with differentiation in substrate selection in obese girls. A higher %LO contribution may help girls to solicit more fat while performing submaximal exercise.

Free-living physical activity and energy expenditure of rural children and adolescents in the Nandi region of Kenya

PURPOSE

To examine the relationship between physical activity and energy demands in children and adolescents with highly active lifestyles.

METHODS

Physical activity patterns of 30 rural Kenyan children and adolescents (14 ± 1 years, mean ± SD) with median body mass index (BMI) z-score = -1.06 [-3.29-0.67] median [range] were assessed by accelerometry over 1 week. Daily energy expenditure (DEE), activity-induced energy expenditure (AEE) and physical activity level (PAL) were simultaneously determined using doubly-labelled water (DLW). Active commuting to school was assessed by global positioning system.

RESULTS

Mean DEE, AEE and PAL were 12.2 ± 3.4, 5.7 ± 3.0 MJ/day and 2.3 ± 0.6, respectively. A model combining body mass, average accelerometer counts per minute and time in light activities predicted 45% of the variance in DEE (p < 0.05) with a standard error of DEE estimate of 2.7 MJ/day. Furthermore, AEE accounted for ∼47% of DEE. Distance to school was not related to variation in DEE, AEE or PAL and there was no association between active commuting and adiposity.

CONCLUSION

High physical activity levels were associated with much higher levels of energy expenditure than observed in Western societies. These results oppose the concept of physical activity being stable and constrained in humans.

Validation of the TracmorD triaxial accelerometer to assess physical activity in preschool children

OBJECTIVES

To assess validity evidence of TracmorD to determine energy used for physical activity in 3-4-year-old children.

DESIGN AND METHODS

Participants were randomly selected from GECKO Drenthe cohort (n = 30, age 3.4 ± 0.3 years). Total energy expenditure (TEE) was measured using the doubly labeled water method. Sleeping metabolic rate (SMR) was measured by indirect calorimetry (Deltatrac). TEE and SMR were used to calculate physical activity level (PAL) and activity energy expenditure (AEE). Physical activity was monitored using a DirectLife triaxial accelerometer, TracmorD with activity counts per minute (ACM) and activity counts per day (ACD) as outcome measures.

RESULTS

The best predictor for PAL was ACM with gender and weight, the best predictor for AEE was ACM alone (backward regression, R(2) = 0.50, P = 0.010 and R2 = 0.31, P = 0.011, respectively). With ACD, the prediction model for PAL included ACD, height, gender, and sleep duration (R2 = 0.48, P = 0.033), the prediction model for AEE included ACD, gender and sleep duration (R2 = 0.39, P = 0.042). The accelerometer was worn for 5 days, but 3 days did not give a different estimated PAL.

CONCLUSION

TracmorD provides moderate-to-strong validity evidence that supports its use to evaluate energy used for physical activity in 3-4-year-old children.

The effects of resistance exercise training on body composition and strength in obese prepubertal children

OBJECTIVE

To assess the effects of resistance exercise training on body composition and muscular strength in obese prepubertal children.

DESIGN

Study participants, who were between the ages of 8 and 12 years, met Tanner I (stage) criteria, had a body mass index ≥ 95th percentile for age and sex, were randomized to either high-repetition, moderate-intensity resistance training (n = 12) or to the non-intervention control group (n = 7) for 12 weeks. Exercise training was performed twice a week for 75 minutes per session. Body composition was assessed using dual energy x-ray absorptiometry and muscular strength was evaluated using a 1-repetition-maximum test.

RESULTS

Exercise-group participants attended 98% of the 24 total sessions and showed a significant increase in body weight (57.6± 13.5 vs 59.6± 14.1 kg), height (144.9± 9 vs 146.6± 10.4 cm), lean body mass (32.6± 6.8 vs 34.0± 7.0 kg), lean body mass index (lean body mass in kg/height2; 15.3± 1.6 vs 15.6± 1.5 kg/m2), arm strength (28.4± 5.8 vs 31.2± 6.0 kg), and leg strength (89.4± 31.7 vs 113.4± 34 2 kg) from baseline measures (P < 0.05). Control group participants also showed significant increases in weight, height, and lean body mass from baseline measures (P < 0.05) but not in arm or leg strength. When the changes in participant body composition and muscular strength were compared between the exercise and control groups, significant differences were found in leg lean mass and leg strength (P < 0.05). There were no changes in percent body fat and fat mass index [FM/height2(kg/m2)] in either group.

CONCLUSION

Resistance training increases leg lean mass and leg strength in obese prepubertal youth and may have a positive effect on overall physical activity and health.

Physical activity, fitness and the energy cost of activities: implications for obesity in children and adolescents in the tropics

The tropics cover a large section of the world in which both developed and developing countries are situated. Rapid socioeconomic development, modernization, urbanization, and globalization have affected both the food market and physical activity (PA), which in turn have propelled the obesity epidemic in the tropics. There is growing concern that overweight and obesity are emerging as major health problems among children and adolescents in the tropics, despite the fact that undernutrition still exists in many of these countries. Physical inactivity, a low metabolic rate, and lack of physical fitness (PF) have been linked to overweight and obesity. Moreover, PF in several tropical countries is declining, and these changes may be a threat to future health, as low PA and PF levels are important risk factors for noncommunicable chronic diseases. Previous studies have reported that the relationships among PA, PF, overweight, and obesity are inconsistent and inconclusive. There is no indication that variances in the energy cost of physical activities lead to obesity. Despite a lack of definite evidence to prove a causal relationship, there is enough certainty that physical inactivity and low fitness levels are linked to overweight and obesity. Hence, people living in tropical countries need to be encouraged to lead a healthier lifestyle by increasing their PA levels and reducing sedentary behaviors to prevent overweight or obesity.

One-year change in energy and macronutrient intakes of overweight and obese inner-city African American children: effect of community-based Taking Action Together type 2 diabetes prevention program

Taking Action Together (TAT) was a controlled community-based intervention protocol developed to reduce risk of T2DM among low-income, high BMI, 9-10 year old African American children. A secondary hypothesis of this study was that there would be greater improvements in the treatment group in dietary intakes and physical activity. To evaluate the primary study objectives, multiple linear regression models were employed, with 1 year change in dietary variables as dependent variables. Intervention group status was the independent variable of interest and BMIz was included as a covariate in all analyses to adjust for group differences in baseline obesity status of the children. The findings from this analysis suggest that 1 year change in dietary intakes in boys was associated with group intervention status, with boys in the treatment group reducing their intakes of energy and fat to a significantly greater extent than boys in the control group. Differences in energy intakes were not significant, however, for girls. Based on the differences in gender response to our comprehensive TAT intervention, we conclude that interventions designed for and delivered only to African American girls might be more successful than those delivered in mixed gender settings.

Childhood obesity and walking: guidelines and challenges

The development and maintenance of excess body mass in many children is partly attributable to levels of physical activity that are lower than the recommended 60 minutes/day. Walking is a recommended form of physical activity for obese children, due to its convenience and perceived ease of adoption. Unfortunately, studies that have used objective physical activity assessment continue to report low step counts and levels of physical activity in obese children. This may be due to physiological and/or biomechanical factors that make walking more difficult for obese children. The purpose of this review is to highlight the current recommended and measured levels of physical activity for children and to discuss the physiological and biomechanical challenges of walking for obese children that may help explain why these children are not meeting physical activity goals.

Obesity and energy balance: is the tail wagging the dog?

The scientific study of obesity has been dominated throughout the twentieth century by the concept of energy balance. This conceptual approach, based on fundamental thermodynamic principles, states that energy cannot be destroyed, and can only be gained, lost or stored by an organism. Its application in obesity research has emphasised excessive appetite (gluttony), or insufficient physical activity (sloth), as the primary determinants of excess weight gain, reflected in current guidelines for obesity prevention and treatment. This model cannot explain why weight accumulates persistently rather than reaching a plateau, and underplays the effect of variability in dietary constituents on energy and intermediary metabolism. An alternative model emphasises the capacity of fructose and fructose-derived sweeteners (sucrose, high-fructose corn syrup) to perturb cellular metabolism via modification of the adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio, activation of AMP kinase and compensatory mechanisms, which favour adipose tissue accretion and increased appetite while depressing physical activity. This conceptual model implicates chronic hyperinsulinaemia in the presence of a paradoxical state of 'cellular starvation' as a key driver of the metabolic modifications inducing chronic weight gain. We combine evidence from in vitro and in vivo experiments to formulate a perspective on obesity aetiology that emphasises metabolic flexibility and dietary composition rather than energy balance. Using this model, we question the direction of causation of reported associations between obesity and sleep duration or childhood growth. Our perspective generates new hypotheses, which can be tested to improve our understanding of the current obesity epidemic, and to identify novel strategies for prevention or treatment.

Obesity: the new childhood disability?

This review addresses the impact of obesity on paediatric physical functioning utilizing the World Health Organization International Classification of Functioning, Disability and Health Framework (ICF). The ICF encompasses functioning (as it relates to all body functions and structures), activities (undertaking a particular task) and participation (in a life situation) with disability referring to impairments in body functions/structures, activity restrictions or participation limitations. Electronic databases were searched for peer-reviewed studies published in English prior to May 2009 that examined aspects of physical functioning in children (≤18 years). Eligible studies (N = 104) were ranked by design and synthesized descriptively. Childhood obesity was found to be associated with deficits in function, including impaired cardiorespiratory fitness and performance of motor tasks; and there was some limited evidence of increased musculoskeletal pain and decrements in muscle strength, gait and balance. Health-related quality of life and the subset of physical functioning was inversely related to weight status. However, studies investigating impacts of obesity on wider activity and participation were lacking. Further research utilizing the ICF is required to identify and better characterize the effects of paediatric obesity on physical function, activity and participation, thereby improving targets for intervention to reduce disability in this population.

Effect of stride frequency on the energy cost of walking in obese teenagers

The aim of this study was to compare the energy cost of obese and non-obese teenagers while walking at their preferred speed and different stride frequencies. Twelve obese and twelve non-obese teenagers walked continuously on the treadmill at their most comfortable speed for 6 periods of 4 min each. Each period corresponded to a specific stride frequency: preferred (PSF), force-driven harmonic oscillator (FDHO), PSF+10%, PSF+20%, PSF-10% and PSF-20%. Cardiorespiratory parameters were collected between the 3rd and 4th minute of each stage, and used to calculate the energy cost of walking (EC). The main results showed a significantly higher cost of walking expressed relative to lean body mass. In addition, a U-shaped relationship between EC and stride frequency was shown in both groups, with PSF and FDHO leading to a significantly lower value compared to all other frequencies. This showed first, that FDHO is a good predictor of PSF and minimal energy cost of walking in both groups, and second, that excess body fat does not affect the relationship between energy expenditure and stride frequency. Walking at lower or higher than preferred frequencies could be used as an exercise mode to promote weight loss in obese teenagers.

Predictors of physical activity energy expenditure in Afro-Caribbean children

BACKGROUND/OBJECTIVES

We hypothesized that maternal size during pregnancy and birth size are determinants of childhood physical activity energy expenditure (PAEE). Also, childhood PAEE is inversely related to adiposity and levels of cardiovascular risk factors.

SUBJECTS/METHODS

The Vulnerable Windows Cohort Study is a longitudinal observational study of 569 Afro-Jamaican mothers recruited from the first trimester and their offspring. Anthropometry, bioelectrical impedance, PAEE (using the Actical monitor) and cardiovascular risk factors (blood pressure, fasting glucose, insulin and lipids) were measured in 124 boys and 160 girls at a mean age of 13.2 years.

RESULTS

Boys had more fat-free mass (FFM) and expended more energy than girls (12.3±3.3 vs 9.6±2.8 kcal/kg/day; P<0.001). Maternal weight was associated with child's PAEE (r=0.29; P<0.001). PAEE was not significantly associated with birth weight. Maternal weight, after adjusting for child's age and sex, was positively associated with the child's FFM, fat mass and %fat (P-values 0.01). Age- and sex-adjusted PAEE was positively associated with FFM, fat mass and % fat (P-values <0.001), but not after adjusting for current weight. Age- and sex-adjusted PAEE was positively associated with triglycerides, insulin and systolic blood pressure (P-values <0.05), but not after adjusting for weight and height. PAEE was associated with fasting glucose after controlling for age, sex, weight and height (r=-0.12; P=0.02).

CONCLUSIONS

Maternal size, but not birth weight, is a determinant of childhood PAEE. PAEE is not strongly associated with childhood body composition, but is inversely related to fasting glucose concentration.

Body size and walking cadence affect lower extremity joint power in children's gait

Obese children move less and with greater difficulty than normal-weight counterparts but expend comparable energy. Increased metabolic costs have been attributed to poor biomechanics but few studies have investigated the influence of obesity on mechanical demands of gait. This study sought to assess three-dimensional lower extremity joint powers in two walking cadences in 28 obese and normal-weight children. 3D-motion analysis was conducted for five trials of barefoot walking at self-selected and 30% greater than self-selected cadences. Mechanical power was calculated at the hip, knee, and ankle in sagittal, frontal and transverse planes. Significant group differences were seen for all power phases in the sagittal plane, hip and knee power at weight acceptance and hip power at propulsion in the frontal plane, and knee power during mid-stance in the transverse plane. After adjusting for body weight, group differences existed in hip and knee power phases at weight acceptance in sagittal and frontal planes, respectively. Differences in cadence existed for all hip joint powers in the sagittal plane and frontal plane hip power at propulsion. Frontal plane knee power at weight acceptance and sagittal plane knee power at propulsion were significantly different between cadences. Larger joint powers in obese children contribute to difficulty performing locomotor tasks, potentially decreasing motivation to exercise.

Energy recommendations for normal weight, overweight and obese children and adolescents: are different equations necessary?

In 2002/2005, separate energy requirement equations were generated by the Institute of Medicine's (IOM) Dietary Reference Intake process for normal weight and overweight/obese children and adolescents. The current paper questions the theoretical rationale of having two sets of equations (based solely on body-weight classification): when body weight is considered, overweight and obese children and adolescents do not seem to differ from their normal weight counterparts in energy expended for basal metabolism or physical activity tasks. However, energy needs for weight maintenance among overweight/obese girls were consistently higher when predicted using the equations for overweight/obese individuals compared with those developed for normal weight individuals. In contrast, among overweight/obese boys, they were consistently lower. Although the differences are within the variability of the estimates, even theoretical support for a higher energy intake (as occurs in girls) seems unwise because of the potential contribution to a higher body mass in children who are already at risk. It is the opinion of the authors that the IOM revisit the use of two separate equations and generate one set that is appropriate for all children and adolescents.

Physical activity: the present in the context of the past

In the broad sense, modern humans have lived in an environment in which physical activity and associated movement skills were central, especially in the context of physical competition with other animals. The physically active lifestyle of earlier human populations has been emphasized, especially the cardiovascular endurance component and energy expenditure, but less attention has been devoted to the gross and fine motor skills that are essential components of this lifestyle. Motor skills developed through practice are important determinants of success and survival in preindustrial societies. In industrial and postindustrial societies, on the other hand, the role of physical activity is different, with prowess in certain areas of physical expertise (e.g., accuracy with projectiles, muscular strength, among others) and prolonged exertion (i.e., cardiovascular endurance) less important for survival. The combined effects of the transition to a sedentary lifestyle and attendant dietary changes have resulted first an epidemic of coronary heart disease and more recently an epidemic of overweight/obesity in postindustrial societies. Although mortality associated with coronary heart disease has declined, due largely to biomedical advances, overweight and obesity have increased concomitantly with population reduction in physical activity (energy expenditure) and increased calorie (energy) consumption. The current scenario begs several questions which have implications for contemporary human biology related to sustaining the pace of cultural change on a biological base that is increasingly being compromised by physical inactivity, overweight, and obesity.

Body size, body composition, and metabolic profile explain higher energy expenditure in overweight children

Lower relative rates of energy expenditure (EE), increased energetic efficiency, and altered fuel utilization purportedly associated with obesity have not been demonstrated indisputably in overweight children. We hypothesized that differences in energy metabolism between nonoverweight and overweight children are attributable to differences in body size and composition, circulating thyroid hormones, sympathetic nervous system, and adrenomedullary activity. A total of 836 Hispanic children, 5-19 y old, participated in 24-h calorimetry, anthropometric, and dual-energy X-ray absorptiometry measurements. Biochemistries were determined by standard techniques. Absolute total EE (TEE) and its components (sleep EE, basal EE, sedentary EE, cycling EE, walking EE, activity EE, nonexercising activity thermogenesis) were higher in overweight children (P = 0.001). Net mechanical energetic efficiency of cycling was lower in overweight children (P = 0.001). Adjusting for body size and composition accounted for differences in TEE, its components, and energetic efficiency. Net carbohydrate and fat utilization did not differ between groups. TEE was independently influenced by sex, Tanner stage, fat free mass, fat mass (FM), fasting serum nonesterified fatty acids (NEFA), leptin, free thyroxine, triiodothyronine, and 24-h urinary norepinephrine and epinephrine. Fat utilization was independently associated with age2, sex, FM, fasting serum NEFA, triacylglycerol, adiponectin, leptin, total thyroxine, and free triiodothyronine. Higher EE in overweight children was largely explained by differences in body size and composition, with minor contributions of thyroid and sympathoadrenal systems. Alterations in EE, energetic efficiency, and substrate utilization were not evident in the overweight children.

Daily physical activity counts vs structured activity counts in lean and overweight Dutch children

The objectives of this study were to compare daily physical activities, and activities performed according to a structured protocol, measured with tri-axial accelerometers (Tracmor-4), between lean and overweight children. Fourteen overweight children (59.8+/-9.5 kg) and fifteen lean matched controls (47.2+/-8.7 kg) wore the Tracmor-4 daily, during 12+/-1.3 h, for one week in their home environment. Of these, 24 children participated in a sports afternoon, where they performed activities according to the same structured protocol. In addition, physical activity was estimated using a modified Baecke questionnaire. Body composition was determined. Total mean Tracmor counts/day were significantly lower for the overweight children than for the lean (overweight: 46.1+/-6.9 vs. lean: 54.4+/-11.2 kCounts/day, p=0.02), while reported activities (Baecke score) were similar. When performing activities according to the structured protocol, there was no difference in mean Tracmor counts between the two groups (overweight: 36.3+/-6.9 vs. lean: 34.7+/-6.6 kCounts, p=0.6). Daily physical activities were inversely related to percentage body fat (r(2)=0.29, p<0.01); structured activities were not. As compared to lean children, overweight children moved less without being aware of it; yet exerted the same movements per activity. We conclude that in overweight children daily physical activities were reduced and structured activities performed according to instructions were not. In order to prevent progressive overweight or obesity, overweight children should take part in as many as possible structured and scheduled sports activities throughout the week, and be encouraged to behave physically active in daily life.

Effects of lifestyle intervention and metformin on weight management and markers of metabolic syndrome in obese adolescents

PURPOSE

The purposes of this study are threefold: to determine what components of the metabolic syndrome are present in obese adolescents, to determine what differences exist in the effects of lifestyle intervention versus lifestyle intervention plus metformin on weight management and select markers of metabolic syndrome in obese adolescents, and to determine which factors predict weight loss in obese adolescents treated with lifestyle changes and metformin.

DATA SOURCES

The study was a secondary data analysis utilizing a retrospective chart review of 63 obese adolescents aged 11 through 18 who were treated for obesity at the LeBonheur Youth Lifestyle Clinic from January 1, 2000, through June 30, 2005. Lifestyle interventions included diet, exercise, and counseling. The medication utilized was metformin. Outcomes evaluated included body mass index, relative body mass index (RBMI), weight, waist and hip circumference, blood pressure, serum lipid levels, fasting plasma glucose, 2-h oral glucose tolerance tests, and insulin levels. Changes in mean values between groups were evaluated using the General Linear Models procedure. Logistic regression was utilized to determine which factors might predict weight loss.

CONCLUSIONS

The metformin group (N= 37) tended to be heavier, older, and had more components of the metabolic syndrome than the nonmetformin group (N= 26). All components of the metabolic syndrome were present in both groups (overall prevalence 55%). Both groups had a downward trend in RBMI, a surrogate marker for weight loss, but only the metformin group had a significant loss in RBMI points from baseline to end. There was a trend toward better diastolic blood pressure at 6 months in the metformin group (p= 0.06), which was not seen in the nonmetformin group. The only predictors of weight loss were higher RBMI (those who were heavier lost more) and the absence of type 2 diabetes mellitus (type 2 DM) (those with type 2 DM were less likely to lose 10 or more points in RBMI).

IMPLICATIONS FOR PRACTICE

All components of the metabolic syndrome are present in obese adolescents. The use of lifestyle changes and lifestyle changes plus metformin both produce some degree of weight loss, but subjects on metformin in this study lost significantly more RBMI points than those on lifestyle changes alone. Subjects with type 2 DM are less likely to lose weight than those without type 2 DM. Larger studies and studies with subjects more representative of the general population need to be carried out to assist in the development of evidence-based practice guidelines.

Physical activity and fitness in an international growth standard for preadolescent and adolescent children

Concepts related to energy expenditure, physical activity and physical fitness, and methods of assessment are briefly considered. Variation in energy expenditure, physical activity, and physical fitness associated with age and sex during childhood and adolescence and relationships between physical activity and physical fitness in children and adolescents are reviewed. Implications of undernutrition and obesity for physical activity and physical fitness, and secular changes in physical activity and physical fitness, are briefly highlighted. The review concludes with specific recommendations for and limitations of inclusion of indicators of physical activity and fitness in the construction of an International Growth Standard for Preadolescent and Adolescent Children.

Basal metabolic rate as a proxy for overnight energy expenditure: the effect of age

Recommendations for daily energy requirements use factorial calculations based on BMR. Expressing total energy requirements as a multiple of BMR is based on the assumption that BMR is equal to overnight metabolic rate (OMR). The objective of the present study was to determine if BMR is an appropriate proxy for OMR in children, young adults and elderly. Data are presented of thirty children (11 (sd 2) years), thirty young adults (25 (sd 5) years) and fifty-nine elderly(61 (sd 5) years). OMR was measured in a respiration chamber while sleep was not hindered and BMR was measured directly afterwards with a ventilated hood system under strictly controlled conditions. The mean ratio of OMR:BMR was 0·92 (sd 0·09) for children, which was significantly different from 1·00 (P<0·001), 1·00 (sd 0·07) for young adults and 1·06 (sd 0·09) for elderly whichwas also different from 1·00 (P<0·001). Foradults, BMR is an appropriate measure of OMR. In children, the use of BMR to estimate OMR wouldintroduce an overestimate and for elderly an underestimate.

Energy requirements of children and adolescents

Total energy expenditure (TEE) was calculated at 1–18 years of age from measurements with doubly labelled water (DLW) in 483 boys and 646 girls, and heart rate monitoring (HRM) in 318 boys and 162 girls. Studies on obese, underweight and stunted groups were not included. TEE of populations with different lifestyles was estimated by factorial calculations in 42 studies on time allocation involving 1982 boys and 1969 girls in developed industrialised countries, and 1236 boys and 1116 girls in developing countries. Quadratic polynomial models were best to predict TEE in boys (TEE(MJ day−1) = 1.298 + 0.265 kg − 0.0011 kg2, r = 0.982, SEE = 0.518) and girls (TEE(MJ day−1) = 1.102 + 0.273 kg − 0.0019 kg2, r = 0.955, SEE = 0.650). TEE at 1–2 years was reduced by 7% based on DLW measurements and TEE estimates of infants. Energy requirements (ER) were calculated adding 8.6 kJ (2 kcal) for each gram of weight gained during growth. Compared with the 1985 FAO/WHO/UNU values1, ER were 18–20% lower from 1 to 7 years of age, 12% lower for boys and 5% lower for girls at 7–10 years, and 12% higher for either gender from 12 years onwards. Differences between industrialised and developing countries, the variance in DLW and HRM studies, and the standard error of the estimate (SEE) of the quadratic predictive equations, suggested that ER should be adjusted after 5 years of age by ±15% in populations with more or less physical activity than an average lifestyle. Physical activity recommendations must accompany dietary recommendations in order to maintain optimal health and reduce the risk of diseases associated with sedentary lifestyles.

Habitual physical activity and sedentary behaviour in a clinical sample of obese children

OBJECTIVE

To objectively measure habitual physical activity and sedentary behaviour in a clinical sample of obese children and to compare with age- and sex-matched non-obese controls.

DESIGN

Pairwise comparison of obese children matched for age and gender with non-obese controls.

SUBJECTS

A total of 116 obese children (body mass index (BMI)> or =98th centile) and 53 non-obese control children (BMI<85th centile). Controls were matched with 53 of the obese children (mean age 8.6, s.d. 2.0 years; 25 M and 28 F).

MEASUREMENT

Habitual physical activity and sedentary behaviour were measured over a 7-day period using CSA accelerometers. Total physical activity (mean accelerometry count per minute (c.p.m.)), percentage of monitored time in sedentary behaviour, light and moderate to vigorous intensity physical activity (MVPA) were compared.

RESULTS

Obese children (n=116) spent on average 80.4% of their monitored time in sedentary behaviour and 2.5% of their monitored time in MVPA. Total activity (mean c.p.m.) was significantly higher in the non-obese group (n=53) than the obese group (n=53), 729 vs 648 c.p.m.; 95% confidence interval (CI) 7, 155. Time spent in sedentary behaviour averaged 80.9% (s.d. 6.6) in the obese group and 79.3% (s.d. 6.2) in the non-obese group, with no significant between-group difference (95% CI -3.9, 0.6). Light intensity activity was similar in the obese and non-obese groups (15.9 vs 17.3%; 95% CI -0.3, 3.0). Participation in MVPA was significantly higher in the non-obese vs obese group (3.9 vs 2.4%; 95% CI 0.6, 2.0).

CONCLUSION

This study supports the hypothesis that a clinical sample of obese children is less physically active than non-obese children, although the difference in total activity and MVPA between the groups was small.

Childhood obesity and the metabolic syndrome

The current epidemic of obesity reflects environmental changes that have an impact on a genetically susceptible population. The scope of obesity and its associated comorbidities warrants its position among the most crucial global public health problems faced today. Society has gained better appreciation for the significance of this problem yet still has much to learn regarding how best to address the obesity crisis. Although strategies for treating individuals who have weight problems successfully continue to evolve, the most profound impacts ultimately will arise from societal changes dictating that all individuals strive to adopt a healthy lifestyle.

Quelle méthode alternative à l'absorptiométrie biphotonique (DEXA) utiliser pour évaluer la composition corporelle des adolescents en surpoids ou obèses ?

CONTEXT

Professionals in charge of overweight and obese children and adolescents need a simple, reliable and precise method for assessing body composition.

OBJECTIVES

To compare body composition as assessed by dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA) and the skinfold thickness (SFT) method in overweight and obese adolescents, and to establish and validate new predictive equations of body composition from BIA measurements using DXA as standard method.

SUBJECTS AND METHODS

Body composition was assessed in 143 obese adolescents (Z-score = 3.2 +/- 1.4) aged 12 to 17 years by DXA, BIA (RJL System, Analycor and Analycor XF models) and SFT (Siri and Slaughter's equations). New prediction equations of fat mass (FM) as assessed by DXA were computed from BIA measurements in a calibration group, and validated in an homologous group of subjects. Results. - The Bland-Altman test showed that compared to DXA, BIA underestimated FM by 2.8 +/- 2.0 kg and 2.3 +/- 2.1 kg using the RJL System and Analycor impedancemeter, respectively (P < 0.001). With the Analycor XF model, FM was underestimated by 3.3 +/-2.6 kg in boys, and over-valued by 0.6 +/- 2.4 kg in girls. On the contrary, the predictive equation of Wabitsch et al. overvalued FM by 6.2 +/- 2.9 kg. The SFT method overvalued FM by 2.1 +/- 5.0 kg in boys and underestimated FM by 2.3 +/- 3.5 kg in girls using Slaughter et al. equation, while Siri's equation underestimated FM by 4.0 +/- 2.9 kg (P < 0.001). The alternative to the DXA method to assess FM was BIA with new prediction equations including gender, body weight, height(2)/resistance and reactance.

CONCLUSION

DXA, BIA and the SFT method were not directly interchangeable. The SFT method was inadequate to assess body composition in overweight and obese adolescents. BIA and new prediction equations could be an alternative to the DXA method in overweight and obese adolescents.

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.

[Knowledge and gaps on the role of nutrition and physical activity on the onset of childhood obesity]

Childhood and adolescent obesity has increased at alarming rates over the last few years, due to the concurrence of a variety of genetic and environmental factors. The aim of this study was to conduct a review of published studies in the past ten years evaluating the development of childhood obesity in relation to energy and macronutrients intake, their distribution throughout the day and physical activity patterns. 31 articles dealing with this subject were selected. Results obtained appear to indicate that reducing dietary fat and increasing dietary carbohydrate intakes along with consuming an adequate breakfast and carrying out leisure time physical activity on a regular basis act as determining factors to prevent childhood and adolescent obesity, even though the strength of the evidence from these studies is low. It should be a priority to conduct follow-up studies with comparable methodologies in Mediterranean countries, in order to establish parameters for the prevention and control of childhood and adolescent obesity.

Energetic cost of physical activity in cystic fibrosis children during Pseudomonas aeruginosa pulmonary exacerbation

Chronic pulmonary infection by Pseudomonas aeruginosa is observed in 50% of patients with cystic fibrosis and requires the use of recurrent intravenous therapy. A decrease of resting energy expenditure (REE) and an increase of physical activity (PA) after intravenous anti-P. aeruginosa therapy (IVAT) is observed while total energy expenditure (TEE) does not change. A decrease in the energetic cost of physical activity (ECPA) could be hypothesized but has never been studied. Our aim was to assess the evolution of ECPA after home IVAT in both standardized condition at hospital and in free-living condition twice before and after IVAT. Sixteen CF patients (nine boys, seven girls) chronically colonized by P. aeruginosa with a mean age of 12.1+/-2.3 years (range 7.1-14.6) were studied before and after IVAT. Each patient passed throughout a visit in hospital: weight, height and fat-free mass were measured. Then, energy expenditure (EE) measured by indirect calorimetry and heart rate (HR) were simultaneously recorded at different levels of PA: REE, and at different intensity of physical activities on a cycloergometer using an incremental increase of the power brake force. Physical activity energy expenditure (PAEE) was computed in laboratory condition using PAEE=EE-BEE (basal energy expenditure). Linear regression between PAEE and power brake force was fitted for each patient before and after IVAT. ECPA in standardized conditions was compared at different range of power brake force using area under the curve (AUC). After coming back at home, 24 h TEE using the heart rate monitoring technique and PA by triaxial accelerometry were simultaneously measured in free-living condition for 24 h during a school day. ECPA in free-living conditions was compared by the ratio PAEE:PA where PAEE=DEE-REE (DEE=daily energy expenditure). After IVAT, median AUC between 60 and 90 W in standardized condition decreased significantly by -15.4% (median 14.9, range 8.8-30.3 vs. median 12.6, range 8.5-17.6; P<0.05, Wilcoxon rank test) while the decrease for lower range of power work load did not reach significance. Spearman correlation was significant between variations of forced expiratory volume in 1 s and variation of AUC at 30-60 W before and after IVAT in standardized condition. In free-living conditions, ratio PAEE/PA did not vary significantly (median 3.4, range 1.6-6.4 vs. median 2.8, range 1.4-4.8; NS). Our data demonstrate a decrease of ECPA after IVAT in standardized conditions for moderate level of PA (60-90 W), but not in free-living conditions. The decrease of ECPA was probably due to a decrease in the energetic cost of breathing after IVAT, that is particularly relevant to promote PA in CF patients.

Overweight and obesity in children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Epidemiological studies suggest that adiposity in children may be associated with a reduced level of physical activity. Children with Attention-Deficit/Hyperactivity Disorder (ADHD) are physically hyperactive as of early childhood and have been shown to exhibit higher levels of motor activity than normal. The aim of our study was to assess if the prevalence of overweight and obesity is lower in a population of boys with ADHD in comparison with the German healthy male reference population of the same age.

DESIGN

Patients were investigated from 1999 until 2001 upon referral to the inpatient and outpatient unit of the Department of Child and Adolescent Psychiatry of the University of Aachen.

SUBJECTS

A total of 97 male patients (mean age 10+/-2 y) with a diagnosis of ADHD according the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), who were free of potentially orexigenic medication and who had no further comorbid diagnosis apart from conduct disorder.

MEASUREMENTS

BMI standard deviation scores (BMI-SDS) were calculated and compared to age-adapted reference value of the German population.

RESULTS

Patients' mean BMI-SDS was significantly higher than the age-adapted reference values of the German population (P=0.038). Our sample included significantly more subjects than expected with a BMI > or =90th percentile (19.6%, P<0.001) and > or =97th percentile (7.2%, P=0.007).

CONCLUSION

Surprisingly, being 'hyperactive' in the sense of the DSM-IV diagnosis of ADHD does not prevent the development or persistence of overweight and obesity in children. The examination of these children might be a helpful approach in the investigation of the relationship between obesity and its contributing psychological and behavioural factors.

Oxygen uptakes adjusted for body composition in normal-weight and obese adolescents

OBJECTIVE

To test whether resting oxygen uptake (VO(2)), submaximal VO(2), and maximal VO(2) (VO(2max)) differs between obese adolescents (n = 18; BMI > 30) and a matched normal-weight control group after adjustment for differences in fat-free mass (FFM) and fat mass (FM).

RESEARCH METHODS AND PROCEDURES

FFM and FM were assessed by DXA. Resting VO(2), submaximal VO(2), and VO(2max) were measured by indirect calorimetry.

RESULTS

There was no difference in resting VO(2) between groups after adjusting for FFM and FM. Submaximal VO(2) did not differ between groups after adjusting for body weight. Percentage VO(2max) and NET VO(2) (VO(2max) - resting VO(2)) were significantly higher in the obese group during submaximal exercise, however not after adjusting for body weight. VO(2max) was not significantly different between groups after adjusting for FFM.

DISCUSSION

When body compositions are appropriately controlled for, resting VO(2), submaximal VO(2), and VO(2max) do not differ between obese and normal-weight adolescents. These data suggested that the higher relative VO(2) observed in obese adolescent subjects is due to their higher FM and not to an impaired VO(2max) even though they may be less physically active.

Energy cost of physical activities in 12-y-old girls: MET values and the influence of body weight

BACKGROUND

Few data exist on the energy cost of specific activities in children. The influence of body weight on the energy cost of activity when expressed as metabolic equivalents (METs) has not been vigorously explored.

OBJECTIVE

To provide MET data on five specific activities in 12-y-old girls and to test the hypothesis that measured MET values are independent of body weight.

SUBJECTS AND METHODS

In 17 12-y-old girls, resting metabolic rate (RMR) and the energy expended while sitting, standing, walking on a flat treadmill at 3.2 and at 4.8 km/h, and walking on a treadmill at a 10% incline at 4.8 km/h were measured using indirect calorimetry. MET values were calculated by dividing the energy expenditure of an activity by the subject's RMR. The influence of body weight was assessed using simple linear regression.

RESULTS

The observed METs were more consistent with published values for similar activities in adults than those offered for children. Body weight was a statistically significant predictor of the MET of all three walking activities, but not the MET of sitting or standing. Body weight explained 25% of the variance in the MET value for walking at 3.2 km/h, 39% for walking at 4.8 km/h, and 63% for walking at a 10% incline at 4.8 km/h.

CONCLUSION

METs for the three walking activities were not independent of body weight. The use of average MET values to estimate the energy cost of these three activities would result in an underestimation of their energy cost in heavier girls and an overestimation in lighter girls. These results suggest that the estimation of total energy expenditure from activity diary, recall, and direct observation data using average MET values may be biased by body weight.

Assessment of energy expenditure associated with physical activities in free-living obese and nonobese adolescents

BACKGROUND

Information on activity patterns and the energy cost of activities is critically missing.

OBJECTIVE

We measured the energy cost of and time devoted to various activities in obese and nonobese adolescents.

DESIGN

Daily energy expenditure (DEE) and its main components were determined in 27 obese and 50 nonobese adolescents aged 12-16 y by using whole-body calorimetry with the same activity program and the heart rate-recording method in free-living conditions.

RESULTS

In whole-body calorimetry, energy expenditures (EEs) during sleep and sedentary activities were 18.9% and 21.5%, respectively, higher in obese subjects than in nonobese subjects (P < 0.001), but not significantly different after adjustment for fat-free mass (FFM). EEs during walking and DEEs were significantly higher in obese than in nonobese subjects, both absolutely (71% and 33%, respectively) and after adjustment for body weight or FFM (16% and 11%, respectively). In free-living conditions, EEs associated with physical activities did not differ significantly between obese and nonobese subjects, but they were 51% lower in obese subjects after adjustment for body weight (P < 0.001). The obese adolescents spent more time in light physical activities but much less time in moderate activities and sports than did the nonobese subjects. The activity-related time equivalent corrected for sedentary EE (ARTE EE(2)) averaged 69 and 122 min/d in obese and nonobese subjects, respectively (P < 0.01).

CONCLUSION

Physical activity is low in obese subjects and can be assessed satisfactorily in both obese and nonobese adolescents by using ARTE EE(2) when DEE and the basal metabolic rate are known.