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

Clarifying main nutritional aspects and resting energy expenditure in children with Smith-Magenis syndrome

Our study aims to define resting energy expenditure (REE) and describe the main nutritional patterns in a single-center cohort of children with Smith-Magenis syndrome (SMS). REE was calculated using indirect calorimetry. Patients' metabolic status was assessed by comparing measured REE (mREE) with predictive REE (pREE). Patients also underwent multidisciplinary evaluation, anthropometric measurements and an assessment of average energy intake, using a 3-day food diary, which was reviewed by a specialized dietitian. Twenty-four patients (13 M) were included, the median age was 9 years (IC 95%, 6-14 years), 84% had 17p11.2 deletion, and 16% had RAI1 variants. REE was not reduced in SMS pediatric patients, and the mREE did not differ from the pREE. In patients with RAI1 variants (16%, n = 3/24), obesity was more prevalent than those with 17p11.2 deletion (100% vs 38%). Lower proteins intake and higher total energy intake were reported in obese and overweight patients, compared to healthy weight children. No significant difference was found between males and females in energy or macronutrient intake.

CONCLUSIONS

In SMS, the onset of obesity is not explained by REE abnormalities, but dietary factors seem to be crucial. Greater concern should be addressed to patients with RAI1 variants. A better understanding of the molecular mechanisms causing obesity in SMS patients could set the basis for possible future targeted therapies.

WHAT IS KNOWN

• More than 90% of SMS patients after the age of 10 are overweight or obese.

WHAT IS NEW

• Onset of overweight and obesity in SMS pediatric patients is not explained by abnormal resting energy expenditure. • The development of syndrome-specific dietary guidelines for SMS patients should be of utmost relevance and are highly needed.

Total energy expenditure measured by doubly labeled water method in children and adolescents: a systematic review

Total energy expenditure (TEE) is essential for understanding the growth, development, and physical activity of children and adolescents. This study aimed to summarize the existing evidence on TEE measured using the doubly labeled water (DLW) technique in children and adolescents aged 1-18 years. Furthermore, this review compared TEE between obese and normal-weight participants. This systematic review used the PubMed, ScienceDirect, Web of Science, and EBSCO databases. These studies were limited to those published in English between January 2000 and December 2021. Articles presenting objectively measured data on the TEE of children and adolescents aged 1-18 years measured using the DLW method were included. Physical activity level (PAL; TEE/basal metabolic rate [BMR]) and BMR data were also obtained. The search strategy identified 2,351 articles, of which 63 (n=4,283 children and adolescents; 45.4% male) met the selection criteria. The participants in the 10 studies were overweight or obese (n=413). In our study, TEE increased in male and female participants aged 1-18 years. PAL increased with age in males (y=0.0272x+1.3887, r2=0.511) and females (y=0.0199x+1.401, r2=0.335), and the slope of PAL with age did not differ between males and females. The TEE of obese and overweight participants was higher than that of normal-weight participants, but the slope of TEE did not differ between normal-weight (y=132.99x+702.24, r2=0.877) and obese individuals (y=136.18x+1,037.9, r2=0.842). In conclusion, this review provides convincing evidence that daily TEE progressively increases with growth in males and females aged 1-18 years.

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.

Differences in Fitness and Academic Attainment between Obese, and Non Obese School-Age Adolescent Handball Players: An Explorative, Cross-Sectional Study

This study investigated differences in physical fitness and academic attainment in obese and non-obese adolescent handball players. A total of 31 males (age: 15.5 ± 1.2 years; body mass: 77.8 ± 17.7 kg; height: 1.71 ± 0.10 m; body mass index (BMI): 26.8 ± 6.9 kg/m2; body fat: 26.4 ± 6.34%) from the Qatar handball first division participated and were divided into two body fat percentage (%BF) groups (i.e., obese or non-obese). Anthropometrics (height, mass, BMI, and %BF) and physical performance testing ability (T-half test for change-of-direction (COD); squat jump (SJ), countermovement jump (CMJ), and 10 and 15 m sprints; medicine ball throw (MBT), and aerobic capacity (Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1)) were determined. Academic attainment was determined through grade point averages (GPA). Non-obese participants had superior performances in mathematics (p < 0.001) and science (p = 0.013), agility T-half test (p = 0.001), CMJ (p < 0.001), and 15 m sprint (p = 0.019). Correlations were found between T-half test and mathematics (r = 0.500) and science (r = 0.484). To conclude, obese school-age handball players have poorer fitness and academic performances than normal body weight adolescents.

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.

Mechanical Efficiency at Different Exercise Intensities Among Adolescent Boys With Different Body Fat Levels

This study investigated the mechanical efficiency (ME) and associated factors in obese, overweight, and normal-weight adolescent boys during incremental cycle exercise test to exhaustion. Forty-five sedentary adolescent boys (13–14 years old) were separated in three groups according to the percentage of fat mass as follows: 15 normal-weight (NW) (body fat: 16.0 ± 1.9%), 15 overweight (OW) (body fat: 24.0 ± 1.6%), and 15 obese (OB) (body fat: 31.0 ± 3.0%). All groups completed an incremental cycle exercise to exhaustion in which energy consumption (E, W), ME (%), lipid oxidation rate (LO, %), plasma epinephrine and norepinephrine concentrations were determined consecutively at rest and at three intensity levels corresponding to 50 and 75% of each participant’s maximal heart rate (50%HRmax and 75%HRmax) and peak oxygen consumption (V˙O_2peak). During the incremental cycle exercise test, plasma epinephrine, and norepinephrine responses as well as ME determined at 50%HRmax, 75%HRmax, and at VO_2peak stages were significantly lower in OB compared to NW and OW individuals (ps < 0.01). Multiple linear regressions showed that body weight (ß = -0.64, p < 0.001), energy consumption (ß = -0.24, p < 0.05) and lipid oxidation (ß = 0.69, p < 0.01) were significant predictors of ME at 50%HRmax. However, at 75%HRmax and V˙O_2peak, significant predictors of ME were epinephrine (ß = 0.34, ß = 0.49, respectively, ps = 0.01), norepinephrine (ß = 0.26, ß = 0.60, respectively, ps < 0.05) and power output (ß = 0.62, ß = 0.71, respectively, ps < 0.01). These findings suggest that excess in body weight exerts a negative effect on ME at a low intensity by increasing energy consumption for obese and overweight adolescent boys, while at higher intensities (75%HRmax and VO_2peak) the lower ME could be better explained by the lower power output and catecholamine responses that were attenuated among obese and overweight adolescent boys.

Plasma ω-3 and ω-6 fatty acids in thyroid diseases

The incidences of nodular goiter (NG), thyroid adenoma (TA), and thyroid cancer (TC) are increasing rapidly; however, the etiologies of these diseases remain unclear. The present study aimed to evaluate the differences in plasma fatty acids among these three thyroid diseases to facilitate etiological research. Four ω-3 and seven ω-6 polyunsaturated fatty acids were measured from 97 TC, 14 TA and 11 NG patient plasma samples with gas chromatography-flame ionization detector. Fatty acids levels were expressed as the percentage of each fatty acid out of the total fatty acids evaluated. The present study identified that the level of 22:6n-3 [median, interquartile range (IQR)] was significantly increased in TA (5.2%, 4.3-6.4%) compared with NG (3.6%, 3.1-4.6%) and TC patients (4.2%, 3.2-4.8%). Though not statistically significant, the levels of 20:5n-3 and 22:5n-3 demonstrated a similar pattern. The level of 22:4n-6 expressed (median, IQR) was significantly increased in NG patients (0.21%, 0.18-0.26%) compared with TA (0.16%, 0.15-0.18%) and TC (0.17%, 0.14-0.22%) patients. Furthermore the fatty acids 18:3n-6, 20:2n-6, 20:3n-6, 20:4:6, and 22:5n-6 demonstrated a similar but statistically insignificant pattern. This suggests that different fatty acids exhibit various etiological roles in NG, TA and TC and warrant further study.

Functional data analysis of sleeping energy expenditure

Adequate sleep is crucial during childhood for metabolic health, and physical and cognitive development. Inadequate sleep can disrupt metabolic homeostasis and alter sleeping energy expenditure (SEE). Functional data analysis methods were applied to SEE data to elucidate the population structure of SEE and to discriminate SEE between obese and non-obese children. Minute-by-minute SEE in 109 children, ages 5-18, was measured in room respiration calorimeters. A smoothing spline method was applied to the calorimetric data to extract the true smoothing function for each subject. Functional principal component analysis was used to capture the important modes of variation of the functional data and to identify differences in SEE patterns. Combinations of functional principal component analysis and classifier algorithm were used to classify SEE. Smoothing effectively removed instrumentation noise inherent in the room calorimeter data, providing more accurate data for analysis of the dynamics of SEE. SEE exhibited declining but subtly undulating patterns throughout the night. Mean SEE was markedly higher in obese than non-obese children, as expected due to their greater body mass. SEE was higher among the obese than non-obese children (p<0.01); however, the weight-adjusted mean SEE was not statistically different (p>0.1, after post hoc testing). Functional principal component scores for the first two components explained 77.8% of the variance in SEE and also differed between groups (p = 0.037). Logistic regression, support vector machine or random forest classification methods were able to distinguish weight-adjusted SEE between obese and non-obese participants with good classification rates (62-64%). Our results implicate other factors, yet to be uncovered, that affect the weight-adjusted SEE of obese and non-obese children. Functional data analysis revealed differences in the structure of SEE between obese and non-obese children that may contribute to disruption of metabolic homeostasis.

Mechanical efficiency in children with different body weight: a longitudinal assessment of the quality cohort

Net mechanical efficiency (MEnet), which reflects the body's ability to transfer energy above resting levels in external work, is similar in young children regardless of their body weights. However, it is unclear whether MEnet remains stable during growth and maturation. We sought to determine whether net mechanical efficiency (MEnet) changes over a period of 3 years in children and to identify the factors associated with possible changes. A total of 169 children participating in the QUALITY (Quebec Adipose and Lifestyle InvesTigation in Youth) cohort completed an incremental cycling test, resulting in the same maximal power output during both visits. For MEnet, resting energy consumption was subtracted from total energy consumption at each exercise stage. Physical activity was measured using an accelerometer worn for 7 days. Participants were measured at year one and again two years later. MEnet did not differ across the visits at the 25, 50 and 75 watt stages. However, the participants exhibited lower MEnet values at follow-up for the 100 and 125 W stages (23(3) vs. 20(1)%; 25(4) vs. 20(2)%; p<0.01). Declines in MEnet correlated positively with declines in moderate-to-vigorous physical activity levels (r=0.78, p<0.05). The declines in moderate-to-vigorous physical activity levels across the visits were identified as significant predictors of MEnet changes at 100 and 125 W over 3 years, accounting for 22% of the relationship. In children, MEnet, determined at high exercise intensity, decreases within a period of three years, and the decrement appeared to be related to moderate-to-vigorous physical activity.

High energy expenditure is not protective against increased adiposity in children

BACKGROUND

Low levels of energy expenditure (TEE) may contribute to excess weight during childhood, but limited longitudinal data exist.

OBJECTIVES

This is to test whether low TEE during the first 6 years of life could predict excess weight status at 8 years.

METHODS

Total energy expenditure from doubly labelled water, weight, stature, waist circumference and fat mass and fat-free mass (FFM) in children at 0.25, 2, 4 and 6 years of age. This cohort includes individuals at high (n = 27) and low risk (n = 26) for childhood obesity, based upon whether pre-pregnant maternal obesity. A linear mixed effects model was fit to TEE. Individual variation was accounted for as a random effect. Residual TEE was calculated for age and individually averaged across time.

RESULTS

Fat-free mass (kg) was highly correlated (R²  = 0.91) with TEE (kcal/day), and waist circumference and sex were also significant predictors of TEE. TEE residual tracked within individuals. TEE residuals did not correlate with either BMI or %fat at age 8 years.

CONCLUSION

Using the residual TEE approach to identify high and low TEE during the first 6 years of life did not explain excess weight at 8 years of life in this cohort of children at high and low risk of obesity based upon maternal obesity status.

Global metabolomic profiling targeting childhood obesity in the Hispanic population

BACKGROUND

Metabolomics may unravel important biological pathways involved in the pathophysiology of childhood obesity.

OBJECTIVES

We aimed to 1) identify metabolites that differ significantly between nonobese and obese Hispanic children; 2) collapse metabolites into principal components (PCs) associated with obesity and metabolic risk, specifically hyperinsulinemia, hypertriglyceridemia, hyperleptinemia, and hyperuricemia; and 3) identify metabolites associated with energy expenditure and fat oxidation.

DESIGN

This trial was a cross-sectional observational study of metabolomics by using gas chromatography-mass spectrometry and ultrahigh-performance liquid chromatography-tandem mass spectrometry analyses performed on fasting plasma samples from 353 nonobese and 450 obese Hispanic children.

RESULTS

Branched-chained amino acids (BCAAs) (Leu, Ile, and Val) and their catabolites, propionylcarnitine and butyrylcarnitine, were significantly elevated in obese children. Strikingly lower lysolipids and dicarboxylated fatty acids were seen in obese children. Steroid derivatives were markedly higher in obese children as were markers of inflammation and oxidative stress. PC6 (BCAAs and aromatic AAs) and PC10 (asparagine, glycine, and serine) made the largest contributions to body mass index, and PC10 and PC12 (acylcarnitines) made the largest contributions to adiposity. Metabolic risk factors and total energy expenditure were associated with PC6, PC9 (AA and tricarboxylic acid cycle metabolites), and PC10. Fat oxidation was inversely related to PC8 (lysolipids) and positively related to PC16 (acylcarnitines).

CONCLUSIONS

Global metabolomic profiling in nonobese and obese children replicates the increased BCAA and acylcarnitine catabolism and changes in nucleotides, lysolipids, and inflammation markers seen in obese adults; however, a strong signature of reduced fatty acid catabolism and increased steroid derivatives may be unique to obese children. Metabolic flexibility in fuel use observed in obese children may occur through the activation of alternative intermediary pathways. Insulin resistance, hyperleptinemia, hypertriglyceridemia, hyperuricemia, and oxidative stress and inflammation evident in obese children are associated with distinct metabolomic profiles.

Mathematical model for the contribution of individual organs to non-zero y-intercepts in single and multi-compartment linear models of whole-body energy expenditure

Mathematical models for the dependence of energy expenditure (EE) on body mass and composition are essential tools in metabolic phenotyping. EE scales over broad ranges of body mass as a non-linear allometric function. When considered within restricted ranges of body mass, however, allometric EE curves exhibit ‘local linearity.’ Indeed, modern EE analysis makes extensive use of linear models. Such models typically involve one or two body mass compartments (e.g., fat free mass and fat mass). Importantly, linear EE models typically involve a non-zero (usually positive) y-intercept term of uncertain origin, a recurring theme in discussions of EE analysis and a source of confounding in traditional ratio-based EE normalization. Emerging linear model approaches quantify whole-body resting EE (REE) in terms of individual organ masses (e.g., liver, kidneys, heart, brain). Proponents of individual organ REE modeling hypothesize that multi-organ linear models may eliminate non-zero y-intercepts. This could have advantages in adjusting REE for body mass and composition. Studies reveal that individual organ REE is an allometric function of total body mass. I exploit first-order Taylor linearization of individual organ REEs to model the manner in which individual organs contribute to whole-body REE and to the non-zero y-intercept in linear REE models. The model predicts that REE analysis at the individual organ-tissue level will not eliminate intercept terms. I demonstrate that the parameters of a linear EE equation can be transformed into the parameters of the underlying ‘latent’ allometric equation. This permits estimates of the allometric scaling of EE in a diverse variety of physiological states that are not represented in the allometric EE literature but are well represented by published linear EE analyses.

Metabolic cost, mechanical work, and efficiency during normal walking in obese and normal-weight children

PURPOSE

This study aimed to investigate the influence of childhood obesity on energetic cost during normal walking and to determine if obese children choose a walking strategy optimizing their gait pattern.

METHOD

Sixteen obese children with no functional abnormalities were matched by age and gender with 16 normal-weight children. All participants were asked to walk along a nearly circular track 30 m in length at a self-selected speed. Spatiotemporal data, kinematics, and ground reaction force were collected during walking using a three-dimensional motion analysis system. Metabolic cost was collected by a portable gas analyzer simultaneously.

RESULTS

The mechanical energy expenditure (MEE) was 72.7% higher in obese children than in normal-weight children. The net metabolic cost was 65.7% higher in obese children. No difference was found in the metabolic rate (J x kg(-1) x m(-1)), normalized MEE (J x kg(-1) x m(-1)) and mechanical efficiency between the obese and normal-weight groups. The obese children walked with a 0.15 m/s slower walking speed, 10.0% shorter cadence, and 30.9% longer double-support phase compared with normal-weight children. In addition, no differences were found in the mediolateral and vertical body center of mass displacement.

CONCLUSION

Body mass played a dominant role in the total metabolic and mechanical cost per stride. Obese children may adopt a walking strategy to avoid an increase in the metabolic cost and the mechanical work required to move their excess body mass.

Mechanical efficiency during a cycling test is not lower in children with excess body weight and low aerobic fitness

OBJECTIVE

The aims of this study were to assess the association between (i) body weight status and mechanical efficiency (ME); and (ii) ME and aerobic fitness in children aged 8-10 years.

DESIGN AND METHODS

The sample included 464 prepubertal children (258 boys). A total of 288 were normal-weight (NW); 84 overweight (OW); and 92 obese (OB). Subjects performed an incremental maximal cycling test with indirect calorimetry. MEcrude (%) was calculated for the first five stages of the protocol (25, 50, 75, 100, and 125 W) as follows: work produced, in watts total energy consumption, in watts(-1) · 100(-1). For MEnet, resting energy consumption was subtracted from total energy consumption. Energy consumption was calculated as follows: (4.94 · respiratory exchange ratio + 16.04) · VO2, in ml · min(-1) · 60(-1).

RESULTS

MEcrude was significantly higher in NW compared to OW and OB children and in OW compared to OB children at 25, 50, 75, 100, and 125 W. In contrast, MEnet did not differ significantly among NW, OW, and OB children. No statistically significant association was found between crude or net ME and peak oxygen consumption (VO2 peak; in ml · kg(-1) · min(-1)); therefore, the ability to transfer chemical energy to mechanical work is maintained in children aged 8-10 years old regardless of body weight status and aerobic fitness. Moreover, higher values of MEcrude during exercise are explained by elevated oxygen consumption at rest and not by energy consumed during physical activity.

CONCLUSIONS

These results highlight that prepubertal children are equally efficient since they are able to perform a physical task such as cycling using the same proportion of energy regardless of their body weight status.

Practical utility and reliability of whole-room calorimetry in young children

The use of whole-room calorimetry (WRC) in young children can increase our understanding of children's energy balance. However, studies using WRC in young children are rare due to concerns about its feasibility. To assess the feasibility of WRC in young children, forty children, aged 4–6 years, were asked to follow a graded activity protocol while in a WRC. In addition, six children participated in two additional resting protocols to examine the effect of diet-induced thermogenesis on resting energy expenditure (REE) measures and the reliability of REE measurement. Refusals to participate and data loss were quantified as measures of practical utility, and REE measured after an overnight fast and after a 90-min fast were compared. In addition, both were compared to predicted BMR values using the Schofield equation. Our results showed that thirty (78·9 %) participants had acceptable data for all intensities of the activity protocol. The REE values measured after a 90-min fast (5·07 (sd 1·04) MJ/d) and an overnight fast (4·73 (sd 0·61) MJ/d) were not significantly different from each other (P= 0·472). However, both REE after an overnight fast and a 90-min fast were significantly higher than predicted BMR (3·96 (sd 0·18) MJ/d) using the Schofield equation (P= 0·024 and 0·042, respectively). We conclude that, with a developmentally sensitive approach, WRC is feasible and can be standardised adequately even in 4- to 6-year-old children. In addition, the effect of a small standardised breakfast, approximately 90 min before REE measurements, is likely to be small.

Energy prediction equations are inadequate for obese Hispanic youth

Assessing energy requirements is a fundamental activity in clinical dietetics practice. A study was designed to determine whether published linear regression equations were accurate for predicting resting energy expenditure (REE) in fasted Hispanic children with obesity (aged 7 to 15 years). REE was measured using indirect calorimetry; body composition was estimated with whole-body air displacement plethysmography. REE was predicted using four equations: Institute of Medicine for healthy-weight children (IOM-HW), IOM for overweight and obese children (IOM-OS), Harris-Benedict, and Schofield. Accuracy of the prediction was calculated as the absolute value of the difference between the measured and predicted REE divided by the measured REE, expressed as a percentage. Predicted values within 85% to 115% of measured were defined as accurate. Participants (n=58; 53% boys) were mean age 11.8±2.1 years, had 43.5%±5.1% body fat, and had a body mass index of 31.5±5.8 (98.6±1.1 body mass index percentile). Measured REE was 2,339±680 kcal/day; predicted REE was 1,815±401 kcal/day (IOM-HW), 1,794±311 kcal/day (IOM-OS), 1,151±300 kcal/day (Harris-Benedict), and, 1,771±316 kcal/day (Schofield). Measured REE adjusted for body weight averaged 32.0±8.4 kcal/kg/day (95% confidence interval 29.8 to 34.2). Published equations predicted REE within 15% accuracy for only 36% to 40% of 58 participants, except for Harris-Benedict, which did not achieve accuracy for any participant. The most frequently accurate values were obtained using IOM-HW, which predicted REE within 15% accuracy for 55% (17/31) of boys. Published equations did not accurately predict REE for youth in the study sample. Further studies are warranted to formulate accurate energy prediction equations for this population.

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.

Recognition of physical activities in overweight Hispanic youth using KNOWME Networks

BACKGROUND

KNOWME Networks is a wireless body area network with 2 triaxial accelerometers, a heart rate monitor, and mobile phone that acts as the data collection hub. One function of KNOWME Networks is to detect physical activity (PA) in overweight Hispanic youth. The purpose of this study was to evaluate the in-laboratory recognition accuracy of KNOWME.

METHODS

Twenty overweight Hispanic participants (10 males; age 14.6 ± 1.8 years), underwent 4 data collection sessions consisting of 9 activities/session: lying down, sitting, sitting fidgeting, standing, standing fidgeting, standing playing an active video game, slow walking, brisk walking, and running. Data were used to train activity recognition models. The accuracy of personalized and generalized models is reported.

RESULTS

Overall accuracy for personalized models was 84%. The most accurately detected activity was running (96%). The models had difficulty distinguishing between the static and fidgeting categories of sitting and standing. When static and fidgeting activity categories were collapsed, the overall accuracy improved to 94%. Personalized models demonstrated higher accuracy than generalized models.

CONCLUSIONS

KNOWME Networks can accurately detect a range of activities. KNOWME has the ability to collect and process data in real-time, building the foundation for tailored, real-time interventions to increase PA or decrease sedentary time.

Physical activity and obesity: biomechanical and physiological key concepts

Overweight (OW) and obesity (OB) are often associated with low levels of physical activity. Physical activity is recommended to reduce excess body weight, prevent body weight regain, and decrease the subsequent risks of developing metabolic and orthopedic conditions. However, the impact of OW and OB on motor function and daily living activities must be taken into account. OW and OB are associated with musculoskeletal structure changes, decreased mobility, modification of the gait pattern, and changes in the absolute and relative energy expenditures for a given activity. While changes in the gait pattern have been reported at the ankle, knee, and hip, modifications at the knee level might be the most challenging for articular integrity. This review of the literature combines concepts and aims to provide insights into the prescription of physical activity for this population. Topics covered include the repercussions of OW and OB on biomechanical and physiological responses associated with the musculoskeletal system and daily physical activity. Special attention is given to the effect of OW and OB in youth during postural (standing) and various locomotor (walking, running, and cycling) activities.

Twelve weeks of moderate aerobic exercise without dietary intervention or weight loss does not affect 24-h energy expenditure in lean and obese adolescents

BACKGROUND

Exercise might have a persistent effect on energy expenditure and fat oxidation, resulting in increased fat loss. However, even without weight loss, exercise results in positive metabolic effects. The effect of an aerobic exercise program on 24-h total energy expenditure (TEE) and its components-basal (BEE), sleep (SEE), and awake sedentary (SEDEE) energy expenditure and substrate oxidation-has not been studied in lean and obese adolescents.

OBJECTIVE

The objective was to test the hypothesis that 24-h energy expenditure and fat oxidation increase in lean and obese adolescents after 12 wk of moderate aerobic exercise without dietary intervention and weight loss.

DESIGN

Twenty-eight postpubertal Hispanic adolescents (13 lean [mean +/- SE: age, 15.3 +/- 0.3 y; body mass index (BMI; in kg/m(2)), 20.2 +/- 0.7; body fat, 18.7 +/- 1.6%] and 15 obese [age, 15.6 +/- 0.3 y; BMI, 33.1 +/- 0.9; body fat, 38.1 +/- 1.4%]) completed a 12-wk aerobic exercise program (4 x 30 min/wk at > or =70% of VO(2 peak)) without weight loss. Energy expenditure and substrate oxidation were quantified by 24-h room calorimetry at baseline and postexercise.

RESULTS

This aerobic exercise program did not affect 24-h TEE, BEE, SEE, or SEDEE in lean or obese participants. In obese adolescents, respiratory quotient (RQ) and substrate oxidation also did not change. In lean adolescents, 24-h RQ and RQ during SEE decreased (both P < 0.01) and fat oxidation increased (P < 0.01).

CONCLUSIONS

A 12-wk aerobic exercise program did not increase TEE, BEE, SEE, or SEDEE in either lean or obese sedentary adolescents. Furthermore, 24-h fat oxidation did not change in the obese adolescents, whereas it increased in the lean adolescents.

Evidence that multiple genetic variants of MC4R play a functional role in the regulation of energy expenditure and appetite in Hispanic children

BACKGROUND

Melanocortin-4-receptor (MC4R) haploinsufficiency is the most common form of monogenic obesity; however, the frequency of MC4R variants and their functional effects in general populations remain uncertain.

OBJECTIVE

The aim was to identify and characterize the effects of MC4R variants in Hispanic children.

DESIGN

MC4R was resequenced in 376 parents, and the identified single nucleotide polymorphisms (SNPs) were genotyped in 613 parents and 1016 children from the Viva la Familia cohort. Measured genotype analysis (MGA) tested associations between SNPs and phenotypes. Bayesian quantitative trait nucleotide (BQTN) analysis was used to infer the most likely functional polymorphisms influencing obesity-related traits.

RESULTS

Seven rare SNPs in coding and 18 SNPs in flanking regions of MC4R were identified. MGA showed suggestive associations between MC4R variants and body size, adiposity, glucose, insulin, leptin, ghrelin, energy expenditure, physical activity, and food intake. BQTN analysis identified SNP 1704 in a predicted micro-RNA target sequence in the downstream flanking region of MC4R as a strong, probable functional variant influencing total, sedentary, and moderate activities with posterior probabilities of 1.0. SNP 2132 was identified as a variant with a high probability (1.0) of exerting a functional effect on total energy expenditure and sleeping metabolic rate. SNP rs34114122 was selected as having likely functional effects on the appetite hormone ghrelin, with a posterior probability of 0.81.

CONCLUSION

This comprehensive investigation provides strong evidence that MC4R genetic variants are likely to play a functional role in the regulation of weight, not only through energy intake but through energy expenditure.

Nutrient adequacy and diet quality in non-overweight and overweight Hispanic children of low socioeconomic status: the Viva la Familia Study

OBJECTIVE

The role of diet quality and nutrient adequacy in the etiology of childhood obesity is poorly understood. The specific aims of these analyses were to assess overall diet quality and nutrient adequacy, and test for association between weight status and diet in children from low socioeconomic status (SES) Hispanic families at high risk for obesity.

DESIGN

A cross-sectional study design was used to assess dietary intake in low-SES Hispanic children with and without overweight who were enrolled in the Viva la Familia Study. Multiple-pass 24-hour dietary recalls were recorded on two random, weekday occasions. Diet quality was evaluated according to the Dietary Guidelines for Americans. Nutrient adequacy was assessed using z scores based on estimated average requirement or adequate intake.

SUBJECTS/SETTING

The study included 1,030 Hispanic children and adolescents, aged 4 to 19 years, in Houston, TX, who participated between November 2000 and August 2004.

STATISTICAL ANALYSIS

STATA software (version 9.1, 2006, STATA Corp, College Station, TX) was used for generalized estimating equations and random effects regression.

RESULTS

Diet quality did not adhere to the Dietary Guidelines for Americans for fat, cholesterol, saturated fatty acids, fiber, added sugar, and sodium. Although energy intake was significantly higher in children with overweight, food sources, diet quality, macro- and micronutrient composition were similar between non-overweight and overweight children. Relative to estimated average requirements or adequate intake levels, mean nutrient intakes were adequate (70% to 98% probability) in the children without and with overweight, except for vitamins D and E, pantothenic acid, calcium, and potassium, for which z scores cannot be interpreted given the uncertainty of their adequate intake levels.

CONCLUSIONS

Whereas the diets of low-SES Hispanic children with and without overweight were adequate in most essential nutrients, other components of a healthful diet, which promote long-term health, were suboptimal. Knowledge of the diets of high-risk Hispanic children will inform nutritional interventions and policy.

Do mechanical gait parameters explain the higher metabolic cost of walking in obese adolescents?

Net metabolic cost of walking normalized by body mass ( CW·BM−1; in J·kg−1·m−1) is greater in obese than in normal-weight individuals, and biomechanical differences could be responsible for this greater net metabolic cost. We hypothesized that, in obese individuals, greater mediolateral body center of mass (COM) displacement and lower recovery of mechanical energy could induce an increase in the external mechanical work required to lift and accelerate the COM and thus in net CW·BM−1. Body composition and standing metabolic rate were measured in 23 obese and 10 normal-weight adolescents. Metabolic and mechanical energy costs were assessed while walking along an outdoor track at four speeds (0.75–1.50 m/s). Three-dimensional COM accelerations were measured by means of a tri-axial accelerometer and gyroscope and integrated twice to obtain COM velocities, displacements, and fluctuations in potential and kinetic energies. Last, external mechanical work (J·kg−1·m−1), mediolateral COM displacement, and the mechanical energy recovery of the inverted pendulum were calculated. Net CW·BM−1 was 25% higher in obese than in normal-weight subjects on average across speeds, and net CW·BM−67 (J·kg−0.67·m−1) was significantly related to percent body fat ( r2 = 0.46). However, recovery of mechanical energy and the external work performed (J·kg−1·m−1) were similar in the two groups. The mediolateral displacement was greater in obese subjects and significantly related to percent body fat ( r2 = 0.64). The mediolateral COM displacement, likely due to greater step width, was significantly related to net CW·BM−67 ( r2 = 0.49). In conclusion, we speculate that the greater net CW·BM−67 in obese subjects may be partially explained by the greater step-to-step transition costs associated with wide gait during walking.

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.

Energy gain and energy gap in normal-weight children: longitudinal data of the KOPS

Population-based prevention of overweight needs evidence-based goals consistent with our present knowledge about energy gap (i.e., daily imbalance between energy intake and energy expenditure resulting in overweight). Longitudinal data of normal-weight children (1,029 girls and 1,028 boys; Kiel Obesity Prevention Study, KOPS) were used to calculate energy gain (i.e., increase in fat mass (FM) and fat-free mass (FFM)) in normal-weight children staying normal weight (persistent children) or becoming overweight (incident children). Taking into account weight gain in proportion to height gain (normal development) energy gap was calculated from increases in FM and FFM exceeding normal development. Children were divided into two groups and were followed from age 6 to 10 (group A) and 10 to 14 years (group B). FM and FFM were measured. Medians of 4-year BMI- (kg/m(2))/weight changes (kg) were +1.8/+13.2 (A) and +3.0/+18.7 (B) in girls, and +1.6/+12.8 (A) and +2.6/21.7 (B) in boys. Corresponding data for FM/FFM (kg) were +3.1/+10.2 (A) and +5.1/12.7 (B) in girls, and +2.3/10.8 (A) and +3.0/18.6 (B) in boys. The 4-year-incidence of overweight (%) were 9.4 (A) and 5.4 (B) in girls, and 11.0 (A) and 3.8 (B) in boys, respectively. Mean energy gains (kcal/day) were 26.8 (A) and 46.4 (B) in girls, and 22.1 (A) and 32.5 (B) in boys. The 90th percentile of energy gap (kcal/day) in incident children were 58.1 (A) and 72.0 (B) in girls and 46.0 (A) and 53.2 (B) in boys. To prevent overweight in children energy gap should not exceed 46-72 kcal/day.