Markers of insulin resistance are associated with fatness and fitness in school-aged children: the European Youth Heart Study

Association between Cluster of Lifestyle Behaviors and HOMA-IR among Adolescents: ABCD Growth Study

Objective: To analyze the association of potential risk factors to health with body fatness and insulin resistance. Baseline measures of the ongoing longitudinal Analysis of Behaviors of Children During (ABCD) Growth Study. Materials and Methods: The sample was composed of 280 adolescents of both sexes (198 boys and 82 girls) aged from 10 to 18 years. Four risk factors were considered, as follows: no sports practice, skipping breakfast, poor sleep quality, and TV viewing. The outcomes considered were insulin resistance (HOMA-IR) and body fatness (densitometer scanner). Age, sex, maturity offset, and ethnicity were treated as covariates. Results: No sports practice and skipping breakfast were associated with higher body fatness (Sports practice: Wald: 8.786; p = 0.003. Breakfast: Wald: 9.364; p = 0.002). Poor sleep quality was related to a greater HOMA-IR index (Wald: 6.013; p = 0.014). Adolescents with ≥3 risk factors presented a higher risk of high HOMA-IR (OR = 4.89 (95%CI: 1.61 to 14.84)) than their counterparts with no risk factors. Conclusion: Lifestyle risk factors seem relevant to affect obesity and insulin resistance, while the aggregation of these risk factors affects insulin resistance, independent of adiposity.

Association between Cluster of Lifestyle Behaviors and HOMA-IR among Adolescents: ABCD Growth Study

Objective: To analyze the association of potential risk factors to health with body fatness and insulin resistance. Baseline measures of the ongoing longitudinal Analysis of Behaviors of Children During (ABCD) Growth Study. Materials and Methods: The sample was composed of 280 adolescents of both sexes (198 boys and 82 girls) aged from 10 to 18 years. Four risk factors were considered, as follows: no sports practice, skipping breakfast, poor sleep quality, and TV viewing. The outcomes considered were insulin resistance (HOMA-IR) and body fatness (densitometer scanner). Age, sex, maturity offset, and ethnicity were treated as covariates. Results: No sports practice and skipping breakfast were associated with higher body fatness (Sports practice: Wald: 8.786; p = 0.003. Breakfast: Wald: 9.364; p = 0.002). Poor sleep quality was related to a greater HOMA-IR index (Wald: 6.013; p = 0.014). Adolescents with ≥3 risk factors presented a higher risk of high HOMA-IR (OR = 4.89 (95%CI: 1.61 to 14.84)) than their counterparts with no risk factors. Conclusion: Lifestyle risk factors seem relevant to affect obesity and insulin resistance, while the aggregation of these risk factors affects insulin resistance, independent of adiposity.

Association between Cluster of Lifestyle Behaviors and HOMA-IR among Adolescents: ABCD Growth Study

Objective: To analyze the association of potential risk factors to health with body fatness and insulin resistance. Baseline measures of the ongoing longitudinal Analysis of Behaviors of Children During (ABCD) Growth Study. Materials and Methods: The sample was composed of 280 adolescents of both sexes (198 boys and 82 girls) aged from 10 to 18 years. Four risk factors were considered, as follows: no sports practice, skipping breakfast, poor sleep quality, and TV viewing. The outcomes considered were insulin resistance (HOMA-IR) and body fatness (densitometer scanner). Age, sex, maturity offset, and ethnicity were treated as covariates. Results: No sports practice and skipping breakfast were associated with higher body fatness (Sports practice: Wald: 8.786; p = 0.003. Breakfast: Wald: 9.364; p = 0.002). Poor sleep quality was related to a greater HOMA-IR index (Wald: 6.013; p = 0.014). Adolescents with ≥3 risk factors presented a higher risk of high HOMA-IR (OR = 4.89 (95%CI: 1.61 to 14.84)) than their counterparts with no risk factors. Conclusion: Lifestyle risk factors seem relevant to affect obesity and insulin resistance, while the aggregation of these risk factors affects insulin resistance, independent of adiposity.

Longitudinal associations of android and gynoid fat mass on cardiovascular disease risk factors in normal weight and overweight boys during puberty

OBJECTIVES

The aim of this longitudinal study was to assess associations between android and gynoid fat distribution and different cardiovascular disease risk factors in normal weight as well as overweight/obese boys during the pubertal period.

METHODS

In total, 146 boys (baseline age 11.9 ±0.6 years) were recruited for a 2-year longitudinal study. Total body fat percentage and android-gynoid fat distribution were measured using DXA. In addition, waist and hip circumference was measured and body mass index (BMI) was calculated. Total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, insulin and glucose were measured, and homeostatic model assessment-insulin resistance (HOMA-IR) was calculated. Tanner stage and physical activity were assessed as covariates.

RESULTS

Overweight subjects had worse values for most of the measured blood parameters (P <0.05). Higher android, gynoid fat mass (FM), and android/gynoid FM ratio were longitudinally associated with higher insulin and HOMA-IR values in both normal weight and overweight boys (P <0.05). In addition, higher android FM and gynoid FM were associated with worse values in HDL cholesterol, LDL cholesterol, and triglycerides in overweight boys (P <0.05).

CONCLUSIONS

Our results suggest that higher android as well as gynoid fat have a strong impact on cardiovascular disease risk factors in both normal weight and overweight boys during the pubertal period. It can be suggested that measurement of fat distribution as android and gynoid fat is important for the assessment of the development or burden of metabolic diseases in boys with different weight statuses.

Physical fitness characteristics of Omani primary school children according to body mass index

BACKGROUND

There is evidence that children with high cardiorespiratory fitness and normal body mass index (BMI) have less risk of non-communicable diseases (NCDs), however limited research was undertaken in Omani children. Therefore the aims of the present study were to describe body composition and physical fitness of a large cohort of Omani school children of both genders, and to investigate the effects of weight status on physical fitness.

METHODS

Three hundred and fourteen Omani school children aged 9 to 10 years old took part in anthropometric assessments, body composition and fitness tests, including handgrip strength, the basketball chest pass, broad jump, 20-m sprint, four 10-m shuttle agility, 30-s sit-up, and multistage fitness test (MSFT).

RESULTS

Obese boys and girls performed worse than normal-weight children in sprint, agility and endurance. In addition, fitness measures in the overweight group and underweight groups were not significantly different from other groups, except a better handgrip strength and poorer MSFT in overweight compared to normal weight girls, and poorer agility performance in underweight girls compared to the three other groups.

CONCLUSIONS

Most fitness measures are lower in obese Omani children, which suggests that they will be more at risk of developing NCDs later in life.

Fatness and Fitness With Cardiometabolic Risk Factors in Adolescents

CONTEXT

The relative importance of fitness and fatness with cardiometabolic risk factors is uncertain during the crucial developmental stage of late adolescence.

OBJECTIVE

We aimed to compare the concurrent influences of cardiorespiratory fitness and fatness in relationship to cardiometabolic risk factors in adolescents from the Western Australian Pregnancy Cohort Study.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional analysis was performed on 1128 participants with complete blood pressure (BP) data and 963 participants with complete blood biochemistry at 17 years of age. Fatness (waist circumference) and cardiorespiratory fitness (physical work capacity 170) were assessed as continuous measures to avoid the use of arbitrary cut points. Analyses used linear regression models adjusted for sex and potential lifestyle confounders.

MAIN OUTCOME MEASURE

Cardiometabolic risk factors.

RESULTS

Fatness was positively associated with systolic BP (coefficient, 0.19; P < 0.001; β coefficient, 0.20), triglycerides (log coefficient, 0.009; P < 0.001; β coefficient, 0.24), low-density lipoprotein cholesterol (coefficient, 0.005; P = 0.007; β coefficient, 0.10), and high-sensitivity C-reactive protein (log coefficient, 0.05; P < 0.001; β coefficient, 0.35). There were no significant effects of fitness on any of these measures. A positive association between homeostasis model of assessment for insulin resistance and fatness (log coefficient, 0.02; P < 0.001; β coefficient, 0.33) was attenuated by fitness (log coefficient, -0.0.18; P < 0.001; β coefficient, -0.18). Fatness was inversely associated with high-density lipoprotein cholesterol (HDL-C) in both sexes (coefficient, -0.006; P < 0.001; β coefficient, -0.23), whereas fitness was positively associated with HDL-C only in females (coefficient, 0.08; P = 0.03; β coefficient, 0.15).

CONCLUSIONS

The adverse effects of central adiposity seen across a broad range of cardiometabolic risk factors were only partially ameliorated by fitness in this adolescent population.

Cardiovascular fitness, physical activity, and metabolic syndrome risk factors among adolescent estonian boys: A longitudinal study

OBJECTIVES

The aim was to examine the changes in metabolic syndrome risk factors over a 2-year period, and to investigate the independent influence of baseline physical activity (PA) and cardiovascular fitness (CVF) on these changes.

METHODS

120 Estonian boys (age at baseline 11.9 ± 0.1 years) were grouped according to baseline PA or CVF/kg (VO_2max/kg ) and CVF/_LBM (VO_2max/LBM ). PA was assessed by 7-day accelerometry. Total cholesterol (TC), high-density lipoprotein (HDL), triglycerides (TRG), insulin and glucose were measured and assessment for insulin resistance (HOMA-IR) and TC/HDL ratio were calculated.

RESULTS

In both CVF/_kg and CVF/_LBM , the low CVF groups had significantly higher values of HOMA-IR (P < 0.009) over time. In TRG and TC/HDL ratio values the only significant difference over time emerged between CVF/_kg groups (P < 0.001). Participants in high metabolic risk CVF/_kg group were 5.9 times more likely to have high HOMA-IR values, 2.9 times more likely to have high triglyceride values, and 3.5 times more likely to have high TC/HDL ratio values (P ≤ 0.045) in the second year follow-up compared to those who were in the low metabolic risk CVF/_kg group. In moderate-to-vigorous PA groups there were no significant differences between HOMA-IR, TRG, and TC/HDL ratio values over time.

CONCLUSIONS

The results of the study indicate that CVF has a stronger longitudinal prediction value compared to moderate to vigorous physical activity in terms of metabolic risk factors in adolescent boys. Fitness remained a significant predictor if the influence of body fatness was removed from the analysis. Am. J. Hum. Biol. 28:782-788, 2016. © 2016Wiley Periodicals, Inc.

Obesity and Insulin Resistance Screening Tools in American Adolescents: National Health and Nutrition Examination Survey (NHANES) 1999 to 2010

OBJECTIVE

To identify which feasible obesity and insulin resistance (IR) screening tools are most strongly associated in adolescents by using a nationally representative sample.

METHODS

Adolescents aged 12.0 to 18.9 years who were participating in the National Health and Nutrition Examination Survey (NHANES) (n=3584) and who were measured for height, weight, waist circumference (WC), triceps and subscapular skinfold thickness, glycated hemoglobin, fasting glucose (FG) and fasting insulin (FI) level were included. Adolescents were split by gender and grouped by body mass index (BMI) percentile. Age- and gender-specific classifications were constructed for each obesity screening tool measure to account for growth and maturation. General linear models were used to establish groups objectively for analysis based on when IR began to increase. Additional general linear models were used to identify when IR significantly increased for each IR measure as obesity group increased and to identify the variance accounted for among each obesity-IR screening tool relationship.

RESULTS

As the obesity group increased, homeostasis model assessment-insulin resistance (HOMA-IR) and FI significantly increased, while FG increased only (above the referent) in groups with BMI percentiles ≥95.0, and glycated hemoglobin level did not vary across obesity groups. The most strongly associated screening tools were WC and FI in boys (R(2)=0.253) and girls (R(2)=0.257). FI had the strongest association with all of the obesity measures. BMI associations were slightly weaker than WC in each in relation to IR.

CONCLUSIONS

Our findings show that WC and FI are the most strongly associated obesity and IR screening tool measures in adolescents. These feasible screening tools should be utilized in screening practices for at-risk adolescents.

Influence of physical fitness on cardio-metabolic risk factors in European children. The IDEFICS study

OBJECTIVE

The aim of the study was to assess the associations of individual and combined physical fitness components with single and clustering of cardio-metabolic risk factors in children.

SUBJECTS/METHODS

This 2-year longitudinal study included a total of 1635 European children aged 6-11 years. The test battery included cardio-respiratory fitness (20-m shuttle run test), upper-limb strength (handgrip test), lower-limb strength (standing long jump test), balance (flamingo test), flexibility (back-saver sit-and-reach) and speed (40-m sprint test). Metabolic risk was assessed through z-score standardization using four components: waist circumference, blood pressure (systolic and diastolic), blood lipids (triglycerides and high-density lipoprotein) and insulin resistance (homeostasis model assessment). Mixed model regression analyses were adjusted for sex, age, parental education, sugar and fat intake, and body mass index.

RESULTS

Physical fitness was inversely associated with clustered metabolic risk (P<0.001). All coefficients showed a higher clustered metabolic risk with lower physical fitness, except for upper-limb strength (β=0.057; P=0.002) where the opposite association was found. Cardio-respiratory fitness (β=-0.124; P<0.001) and lower-limb strength (β=-0.076; P=0.002) were the most important longitudinal determinants. The effects of cardio-respiratory fitness were even independent of the amount of vigorous-to-moderate activity (β=-0.059; P=0.029). Among all the metabolic risk components, blood pressure seemed not well predicted by physical fitness, while waist circumference, blood lipids and insulin resistance all seemed significantly predicted by physical fitness.

CONCLUSION

Poor physical fitness in children is associated with the development of cardio-metabolic risk factors. Based on our results, this risk might be modified by improving mainly cardio-respiratory fitness and lower-limb muscular strength.

Cardiorespiratory fitness is positively associated with a healthy dietary pattern in New Zealand adolescents

OBJECTIVE

To examine the association between cardiorespiratory fitness and dietary patterns in adolescents.

DESIGN

Food choice was assessed using the validated New Zealand Adolescent FFQ. Principal components analysis was used to determine dietary patterns. Trained research assistants measured participants' height and body mass. Cardiorespiratory fitness was assessed in a subset of participants using the multistage 20 m shuttle run. The level and stage were recorded, and the corresponding VO2max was calculated. Differences in mean VO2max according to sex and BMI were assessed using t tests, while associations between cardiorespiratory fitness and dietary patterns were examined using linear regression analyses adjusted for age, sex, school attended, socio-economic deprivation and BMI.

SETTING

Secondary schools in Otago, New Zealand.

SUBJECTS

Students (n 279) aged 14-18 years who completed an online lifestyle survey during a class period.

RESULTS

Principal components analysis produced three dietary patterns: 'Treat Foods', 'Fruits and Vegetables' and 'Basic Foods'. The 279 participants who provided questionnaire data and completed cardiorespiratory fitness testing had a mean age of 15·7 (sd 0·9) years. Mean VO2max was 45·8 (sd 6·9) ml/kg per min. The 'Fruits and Vegetables' pattern was positively associated with VO2max in the total sample (β=0·04; 95%CI 0·02, 0·07), girls (β=0·06; 95% CI 0·03, 0·10) and boys (β=0·03; 95% CI 0·01, 0·05).

CONCLUSIONS

These results indicate that increase in cardiorespiratory fitness was associated with a healthier dietary pattern, suggesting both should be targeted as part of a global lifestyle approach. Longitudinal studies are needed to confirm this association in relation to health outcomes in New Zealand adolescents.

Targeting skeletal muscle mitochondria to prevent type 2 diabetes in youth

The prevalence of type 2 diabetes (T2D) has increased dramatically over the past two decades, not only among adults but also among adolescents. T2D is a systemic disorder affecting every organ system and is especially damaging to the cardiovascular system, predisposing individuals to severe cardiac and vascular complications. The precise mechanisms that cause T2D are an area of active research. Most current theories suggest that the process begins with peripheral insulin resistance that precedes failure of the pancreatic β-cells to secrete sufficient insulin to maintain normoglycemia. A growing body of literature has highlighted multiple aspects of mitochondrial function, including oxidative phosphorylation, lipid homeostasis, and mitochondrial quality control in the regulation of peripheral insulin sensitivity. Whether the cellular mechanisms of insulin resistance in adults are comparable to that in adolescents remains unclear. This review will summarize both clinical and basic studies that shed light on how alterations in skeletal muscle mitochondrial function contribute to whole body insulin resistance and will discuss the evidence supporting high-intensity exercise training as a therapy to circumvent skeletal muscle mitochondrial dysfunction to restore insulin sensitivity in both adults and adolescents.

Fitness level and body composition indices: cross-sectional study among Malaysian adolescent

BACKGROUND

The importance of fitness level on the well-being of children and adolescent has long been recognised. The aim of this study was to investigate the fitness level of school-going Malaysian adolescent, and its association with body composition indices.

METHODS

1071 healthy secondary school students participated in the fitness assessment for the Malaysian Health and Adolescents Longitudinal Research Team (MyHEART) study. Body composition indices such as body mass index for age, waist circumference and waist height ratio were measured. Fitness level was assessed with Modified Harvard Step Test. Physical Fitness Score was calculated using total time of step test exercise and resting heart rates. Fitness levels were divided into 3 categories - unacceptable, marginally acceptable, and acceptable. Partial correlation analysis was used to determine the association between fitness score and body composition, by controlling age, gender, locality, ethnicity, smoking status and sexual maturation. Multiple regression analysis was conducted to determine which body composition was the strongest predictor for fitness.

RESULTS

43.3% of the participants were categorised into the unacceptable fitness group, 47.1% were considered marginally acceptable, and 9.6% were acceptable. There was a significant moderate inverse association (p < 0.001) between body composition with fitness score (r = -0.360, -0.413 and -0.403 for body mass index for age, waist circumference and waist height ratio, respectively). Waist circumference was the strongest and significant predictor for fitness (ß = -0.318, p = 0.002).

CONCLUSION

Only 9.6% of the students were fit. There was also an inverse association between body composition and fitness score among apparently healthy adolescents, with waist circumference indicated as the strongest predictor. The low fitness level among the Malaysian adolescent should necessitate the value of healthy lifestyle starting at a young age.

Leptin, vitamin D, and cardiorespiratory fitness as risk factors for insulin resistance in European adolescents: gender differences in the HELENA Study

The purpose of this study was to identify the relevance of a set of risk factors for insulin resistance in adolescents from Europe and to consider their possible gender-specific associations. The Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study (HELENA-CSS) was conducted in 1053 European adolescents (mean age, 14.9 years) in a school setting in 9 countries. Three anthropometric markers of body fat and a dietary index were calculated. Total energy intake was estimated from a questionnaire. C-reactive protein, leptin, and vitamin D were assessed, and physical activity, cardiorespiratory fitness, and muscular strength were measured. Center, socioeconomic status, pubertal status, and season were used as potential confounders. The main outcome was the homeostasis model assessment used as a marker of insulin resistance. Correlations, analyses of covariance, and logistic regression models were used. In males, leptin was the only risk factor for insulin resistance after adjusting for confounders including markers of body fat (odds ratios (ORs) from 1.49 to 1.60). In females, leptin, vitamin D, and fitness were the remaining independent risk factors for insulin resistance after adjustments (OR 2.11; 95% confidential interval (CI) 1.29-3.45; OR 0.50, 95% CI 0.31-0.80; and OR 0.54, 95% CI 0.33-0.87, respectively). Our observations suggest a gender dimorphism in the identification of risk factors for high insulin resistance. Preventive strategies should focus on improving modifiable factors such as cardiorespiratory fitness and on ensuring vitamin D sufficiency. Randomized controlled trials focusing on these strategies are necessary to test their efficacy.

Evaluation of Body Mass Index (BMI) Percentile cut-off Levels with Reference to Insulin Resistance: A Comparative Study on South Indian Obese and Non-Obese Adolescents

OBJECTIVES

To investigate the relationship of Body Mass Index (BMI) percentile cut off with Homeostasis Model Assessment-Insulin Resistance (HOMA-IR), a surrogate marker for insulin resistance in obese, overweight and non-obese adolescents.

STUDY DESIGN

A cross-sectional analysis of 120 adolescents (divided into sixty overweight/obese and an equal number of non-obese) was performed on nondiabetic, nonpregnant (11 to 18 year old school going) adolescents in south Indian (Puducherry) population. The main outcome measure of insulin resistance was calculated as HOMA-IR (greater than 3.16). Obesity was defined as per the BMI criteria, BMI greater than or equal to 95(th) percentile,overweight greater than or equal to 85(th) percentile and non-obese less than 84.9(th) percentile. All adolescents were subjected to analysis of anthropometric parameters that included weight, height and BMI (body mass index). Biochemical parameters, namely venous plasma glucose (fasting) and venous plasma insulin (fasting) were included for insulin resistance calculation by HOMA-IR.

RESULTS

Having a BMI of greater than or equal to 85(th) percentilewas associated with high HOMA-IR levels. As the BMI percentile increased, HOMA-IR levels also increased. Prevalence of insulin resistance for a BMI percentile of less than 84.9 was nil. Prevalence of insulin resistance for a BMI percentile of 85-94.9 was 26%.Prevalence of insulin resistance for BMI of greater than or equal to 95(th) percentile was 64%.

CONCLUSION

Insulin resistance is highly prevalent in obese and overweight adolescents as compared to that in non-obese adolescents. The onset of Impaired Fasting Glucose (IFG) is associated with the development of severe hyper-insulinaemia in obese adolescents and early primordial and primary prevention can thus alleviate the burden of future cardiometabolic disorders.

Restrictive pulmonary deficit is associated with inflammation in sub-optimally controlled obese diabetics

Caribbean data linking inflammation, pulmonary dysfunction and diabetes is unavailable. Spirometry, acanthosis nigricans, hs-CRP were assessed in 109 type 2 diabetics (43% males) mean age=55.6 years, BMI=29.29 kg/m(2), waist circumference=103.86 cm. Residual FEV1/FVC increased with age (P=0.005), BMI (P=0.011) and waist circumference (P=0.003). Residual FVC related inversely to hs-CRP (-0.178), P<0.06) systolic (-0.028, P<0.031), diastolic (-0.247, P<0.010) pressure and weight (-0.25, P<0.009). Residual FEV1 related inversely to diastolic pressure (-0.219, P<0.023), hs-CRP (-0.234, P<0.015), acanthosis nigricans (-0.029, P<0.029). HbA1C and residual FEV1 predict high hs-CRP (P=0.011, P=0.046). Low FVC with inflammation presents in poorly controlled obese diabetics.

Managing cardiovascular risk in overweight children and adolescents

The scientific, medical, and lay communities are currently confronted with a serious medical and public health problem related to the marked non-remitting worldwide epidemic of obesity. This ever-increasing prevalence of obesity is accompanied by a host of inherently associated co-morbidities. As a result, obesity is fast becoming the major cause of premature death in the developed world. As pediatric and adult cardiologists, we have seen a dramatic increase in office referrals of overweight and obese children and adolescents, who already have obesity-related degenerative disease processes such as hypertension, dyslipidemia, the metabolic syndrome, and type 2 diabetes mellitus, as well as manifestations of early preclinical atherosclerotic cardiovascular disease, not previously observed in this age group. This article presents a review of the literature and recent scientific statements and recommendations issued by the American Heart Association (AHA) and the American Academy of Pediatrics (AAP) regarding the metabolic abnormalities associated with obesity, including newer identification and treatment strategies for obesity, dyslipidemia, and early subclinical coronary artery disease seen in high-risk children and adolescents.

Does Regular Exercise without Weight Loss Reduce Insulin Resistance in Children and Adolescents?

Despite considerable efforts to tackle childhood obesity, it is recognized as one of the biggest health problems globally. Childhood obesity is a leading cause of many comorbid conditions such as metabolic syndrome and insulin resistance as well as type 2 diabetes. A strong body of evidence suggests that regular exercise without calorie restriction or weight loss is associated with reduced insulin resistance as well as improved insulin sensitivity in overweight and obese adults. However, despite the well-known benefits associated with regular exercise alone, the independent role of exercise training without calorie restriction on insulin resistance is still uncertain in youth. Some studies observed that both the aerobic and resistance type of exercise training without calorie restriction resulted in meaningful changes in insulin sensitivity, suggesting that exercise alone is an effective therapeutic strategy for reducing insulin resistance in overweight and obese youth. However, only few studies are available on the optimal dose of exercise training without calorie restriction or preferred exercise modality for reducing insulin resistance, which warrants further investigations in the pediatric population.

Physical activity is related to insulin sensitivity in children and adolescents, independent of adiposity: a review of the literature

In adults, there is evidence that physical activity effectively improves insulin sensitivity regardless of adiposity. Whether this is also the case in children and adolescents is less clear. Clarifying this matter may help to identify the best outcomes to target in exercise programs for these age groups, where changes in adiposity may not always be desirable or realistic. A review of the literature was conducted on studies that examined the relationships of physical activity, cardiorespiratory fitness and strength with insulin sensitivity independent of adiposity in children and adolescents. Experimental (intervention) and correlational (longitudinal and cross-sectional) studies on participants ages 18 years and younger were identified. A total of 42 studies were included in this review. Sample sizes in the studies ranged from 14 to 4955 participants, with individual ages ranging from 5 to 19 years. A significant relationship with insulin sensitivity existed in 78% of studies on physical activity, 69% of studies on cardiorespiratory fitness and 66% of studies on strength. In studies that examined both physical activity and cardiorespiratory fitness concurrently, evidence suggests that they are both correlated with insulin sensitivity independent of adiposity, especially when physical activity is at higher intensities. However, the strength of this relationship might be influenced by study design, measurement techniques and participant characteristics. This is the first review of its type to take research design into account and to examine study outcomes according to participant ethnicity, gender, age, pubertal status and weight status.

How are physical activity, fitness, and sedentary behavior associated with insulin sensitivity in children?

OBJECTIVE

To describe the associations among moderate-to-vigorous physical activity (MVPA), fitness, sedentary behavior (SB), and insulin sensitivity (IS).

RESEARCH DESIGN AND METHODS

Data were drawn from the baseline assessment of the QUALITY cohort, which included 630 white youth (aged 8-10 years at recruitment), with at least one obese biological parent. IS was measured by two fasting indices (insulin, homeostasis model assessment of insulin resistance) and an oral glucose tolerance test (OGTT)-based index (Matsuda IS index [Matsuda-ISI]). Fitness was measured by Vo(2peak); percent fat mass (PFM) was measured by dual-energy X-ray absorptiometry; 7-day MVPA was measured with accelerometry. SB indicators included average hours daily of self-report screen time (SBst), and average minutes daily at <100 counts/min from accelerometry (SBacc). Multivariable linear regression models were adjusted for age, sex, season, and puberty.

RESULTS

MVPA and SBacc were independently associated with IS, but this was no longer statistically significant after accounting for PFM. SBst was negatively associated with IS in girls only, even after controlling for physical activity (PA), fitness, and adiposity; for each additional hour of SBst daily, IS decreased by 4.6-5.6% across all IS indices. Fitness was positively associated with IS (measured by Matsuda-ISI) after accounting for PA, SB, and PFM; for every 1 unit increase in Vo(2peak), Matsuda-ISI increased by approximately 1.0% (P < 0.05).

CONCLUSIONS

In children with an obese parent, PA and SBacc are associated with IS, but this association is mediated by adiposity. SBst is negatively associated with IS in girls, beyond its known impact on adiposity. Finally, fitness is independently associated with better IS measured by OGTT.

Physical activity, fitness, and serum leptin concentrations in adolescents

OBJECTIVE

To examine the association of physical activity and fitness with leptin concentrations in European adolescents, after taking into account several potential confounders including total body fat (TBF).

STUDY DESIGN

We conducted a cross-sectional study in a school setting for the Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study. This study included 902 (509 girls) adolescents aged 12.5-17.5 years. Weight, height, and TBF (sum of 6 skinfold thickness) were measured, and fat free mass and body mass index were calculated. Physical activity was assessed by accelerometry. Physical fitness was assessed by the handgrip, standing long jump, 4 × 10-m shuttle run, and 20-m shuttle run tests. Serum fasting leptin, insulin, and glucose concentrations were measured, and homeostasis model assessment was computed. Multiple linear regression models were used.

RESULTS

Vigorous physical activity and fitness tests (all P < .05) were negatively associated with leptin, independently of several confounders including TBF and homeostasis model assessment. These associations remained significant after further controlling for each other (physical activity and fitness).

CONCLUSION

These results suggest that vigorous physical activity and fitness moderate the levels of leptin concentrations, regardless of relevant confounders including TBF. Intervention programs addressed to increase high intensity physical activity and fitness as well as to assess its impact on leptin concentration are required.

Centile curves and normative values for the twenty metre shuttle-run test in English schoolchildren

The aim of this study was to provide normative data for performance on the 20 m shuttle-run test of cardiorespiratory fitness in English schoolchildren. A total of 7366 10-16 year olds completed the 20 m shuttle-run test. We expressed performance as the number of shuttles completed, test score (shuttles and levels) and estimated peak oxygen consumption (VO2peak). We calculated descriptive statistics for each age-sex group to construct percentile curves and tables. To assess the cardiorespiratory fitness of our sample, we calculated the number of participants who fell below proposed cut-offs for low cardiorespiratory fitness based on either completed shuttles or VdotO2peak. These cut-offs did not agree in terms of frequency of classification. The classification based on estimated VO2peak suggested low fitness was more prevalent in males and that the incidence of low fitness increased with age in both sexes. These are the first normative data for shuttle-run performance in English youth and can now be used to interpret data from this cardiorespiratory fitness test. The two cut-offs used for low fitness did not agree and future research should establish a cut-off for test performance which can predict present or future ill-health.

Pubertal muscle mass and diabetes markers in Chinese adolescents

OBJECTIVES

Diabetes is common in China despite a relatively nonobese population. We hypothesized that testosterone driven muscle mass acquisition at puberty may be relevant. We examined the associations of testosterone with muscle mass and of muscle mass with fasting glucose in Chinese adolescents.

METHODS

In 40 adolescents (20 boys and 20 girls, age 12.9 ± 0.1 years) from Hong Kong's "Children of 1997" birth cohort, we used multivariable linear regression to assess adjusted associations of testosterone and fasting glucose (from a morning blood sample) with muscle and fat mass from a dual-energy X-ray absorptiometry scan.

RESULTS

Testosterone was positively associated with muscle mass (0.05 kg, 95% confidence interval (CI) 0.01 to 0.09, per pg/ml testosterone). Muscle mass was associated with lower glucose (-0.04 mmol/l, 95% CI -0.08 to -0.01 per kg muscle mass) adjusted for sex and fat mass.

CONCLUSIONS

Environmentally driven muscle mass acquisition at puberty could influence diabetes.

Cardiorespiratory fitness, metabolic risk, and inflammation in children

The aim of this study was to investigate the independent associations among cardiorespiratory fitness, metabolic syndrome (MetS), and C-reactive protein (CRP) in children. The sample consisted of 112 children (11.4  ±  0.4 years). Data was obtained for children's anthropometry, cardiorespiratory fitness, MetS components, and CRP levels. MetS was defined using criteria analogous to the Adult Treatment Panel III definition. A MetS risk score was also computed. Prevalence of the MetS was 5.4%, without gender differences. Subjects with low fitness showed significantly higher MetS risk (P < 0.001) and CRP (P < 0.007), compared to the high-fitness pupils. However, differences in MetS risk, and CRP between fitness groups decreased when adjusted for waist circumference. These data indicate that the mechanisms linking cardiorespiratory fitness, MetS risk and inflammation in children are extensively affected by obesity. Intervention strategies aiming at reducing obesity and improving cardiorespiratory fitness in childhood might contribute to the prevention of the MetS in adulthood.

Muscular strength and markers of insulin resistance in European adolescents: the HELENA Study

The aim of the study was to examine the association of muscular strength with markers of insulin resistance in European adolescents. The study comprised a total of 1,053 adolescents (499 males; 12.5-17.5 years) from ten European cities participating in the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) Cross-Sectional Study. Muscular strength was measured by the handgrip strength and standing long jump tests. Cardiorespiratory fitness was measured by the 20-m shuttle run test. Fasting insulin and glucose were measured and the homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) indices were calculated. Weight, height, waist circumference and skinfold thickness were measured, and body mass index (BMI) was calculated. In males, the handgrip strength and standing long jump tests were negatively associated with fasting insulin and HOMA (all P < 0.05) after controlling for pubertal status, country and BMI or waist circumference. When skinfold thickness was included in the model, the association became non-significant. In females, the standing long jump test was negatively associated with fasting insulin and HOMA (all P < 0.001) after controlling for pubertal status, country and surrogate markers of total or central body fat (BMI, waist circumference or skinfold thickness). Findings were retained in males, but not in females after controlling for cardiorespiratory fitness. The findings of the present study suggest that preventive strategies should focus not only on decreasing fatness and increasing cardiorespiratory fitness but also on enhancing muscular strength.

Comparison of cardiorespiratory fitness and body mass index between rural and urban youth: findings from the East of England Healthy Hearts Study

BACKGROUND

The aim of the present study was to determine if there were differences in cardiorespiratory fitness (CRF) and body mass index (BMI) in rural versus urban youth.

METHODS

We measured BMI in 6628 10.0-15.9-year-olds and classified them as normal weight, overweight or obese. CRF was assessed with a 20-m shuttle-run test and subjects were classified as unfit, fit or highly fit. Rural or urban dwelling was calculated from postcodes.

RESULTS

There were no differences in frequency of BMI categories or CRF between rural and urban children (<13 years) or adolescents (>13 years). Rural adolescents were less likely to be fit (OR = 0.80; 95%CI 0.67-0.96) or highly fit (OR = 0.69; 95%CI 0.55-0.86) independent of their age, sex, race or level of deprivation.

CONCLUSIONS

Whilst there were no differences evident in children <13 years, rural adolescents were significantly less likely to meet criterion-based cut-off points for CRF. Research to elucidate why such differences exist is warranted.

Development of youth percent body fat standards using receiver operating characteristic curves

BACKGROUND

Few studies have identified health-related criterion standards of percent body fat (%BF) in U.S. youth. Further, existing standards are static thresholds (e.g., 25%, 30%) and do not account for normal growth and maturation.

PURPOSE

The purpose of this study was to identify thresholds of %BF in youth linked to metabolic syndrome in a large sample of U.S. children and adolescents.

METHODS

Percent fat was derived from the skinfold thicknesses of those aged 12-18 years, from the National Health and Nutrition Examination Survey (NHANES [1999-2004, N=1966]). Metabolic syndrome was classified using previously published standards based on the National Cholesterol Education Program/Adult Treatment Panel III adult values at age 20 years. Using %BF z-scores as the test and metabolic syndrome as the criterion, receiver operating characteristic (ROC) curve analysis was used to identify %BF thresholds.

RESULTS

ROC analysis indicated that %BF can be used with moderate accuracy to identify metabolic syndrome in adolescents. %BF thresholds of 22.3% and 35.1% in boys and 31.4% and 38.6% in girls (at age 18 years) were found to be indicative of "low" and "high" metabolic syndrome risk.

CONCLUSIONS

Age- and gender-specific %BF thresholds for creating separate risk groups were identified in relation to metabolic syndrome status. The selected thresholds identify adolescents with unfavorable metabolic profiles. These values could be extrapolated to younger children using previously created %BF centiles, which potentially allows for earlier identification and intervention of at-risk youth if tracking of current %BF was maintained.

Percent body fat and chronic disease risk factors in U.S. children and youth

BACKGROUND

The dramatic increase in pediatric obesity has renewed interest in accurate methods and screening indexes for identifying at-risk children and youth. Whether age-specific standards are needed is a factor that remains uncertain.

PURPOSE

This study was designed to describe the age-specific fatness-risk factor relationship in boys and girls across a wide age range.

METHODS

Data were from 12,279 white, black, and Mexican-American children and adolescents from the National Health and Nutritional Examination Surveys (NHANES) III (1998-1994) and IV (1999-2004). Children were grouped based on percent fat, estimated from subscapular and triceps skinfolds, and the age-specific relationships between percent fat and chronic disease risk factors (e.g., blood pressure, lipids and lipoprotein levels, glucose, insulin, and circulating C-reactive protein levels) were described in boys and girls, aged 6-18 years.

RESULTS

Percent fat was significantly related to risk factor levels. At higher levels of percent fat, the prevalence of adverse cardiovascular disease risk factors was higher, particularly above 20% fat in boys and above 30% fat in girls. In boys and girls, the interaction term age by percent fat was a significant predictor of risk factors, whereas the percent fat by race interaction term was nonsignificant.

CONCLUSIONS

The results demonstrate a strong relationship between chronic disease risk factors and percent fat in children and youth that varies by age in boys and girls.

Lactase persistence and milk consumption are associated with body height in Swedish preadolescents and adolescents

BACKGROUND

Body height is a classic polygenic trait. About 80%-90% of height is inherited and 10%-20% owed to environmental factors, of which the most important ones are nutrition and diseases in preadolescents and adolescents.

OBJECTIVE

The aim of this study was to explore potential relations between the LCT (lactase) C>T-13910 polymorphism, milk consumption, and body height in a sample of Swedish preadolescents and adolescents.

DESIGN

In a cross-sectional study, using a random sample of preadolescents and adolescents (n = 597), dietary intakes were determined. Anthropometric measurements including sexual maturity (Tanner stage) and birth weight were assessed. Parental body height and socio-economic status (SES) were obtained by questionnaires. Genotyping for the LCT C>T-13910 polymorphism that renders individuals lactase persistent (LP) or lactase non-persistent (LNP) was performed by DNA sequencing. Stepwise backward multivariate linear regression was used.

RESULTS

Milk consumption was significantly and positively associated with body height (β = 0.45; 95% CI: 0.040, 0.87, p = 0.032). Adjustments were performed for sex, parental height, birth weight, body mass index (BMI), SES, and Tanner stage. This model explains 90% of the observed variance of body height (adjusted R(2) = 0.89). The presence of the -13910 T allele was positively associated with body height (β = 2.05; 95% CI: 0.18, 3.92, p = 0.032).

CONCLUSIONS

Milk consumption is positively associated with body height in preadolescents and adolescents. We show for the first time that a nutrigenetic variant might be able to explain in part phenotypic variation of body height in preadolescents and adolescents. Due to the small sample size further studies are needed.

Insulin sensitivity at childhood predicts changes in total and central adiposity over a 6-year period

OBJECTIVE

To examine the associations of insulin resistance at childhood with adiposity changes over a 6-year period (from 9 to 15 years) in a sample of 659 Swedish and Estonian children (52.7% girls) participating in the European Youth Heart Study.

RESEARCH, DESIGN AND METHODS

We measured weight, height, waist circumference, biceps, triceps, subscapular, suprailiac, and medial calf skinfolds, and we calculated body mass index (BMI), sum of five skinfolds, and body fat percentage. Fasting plasma glucose and insulin were measured and homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Changes in puberty stage, sex, centre and the corresponding baseline adiposity values were used as confounders in all analysis.

RESULTS

HOMA-IR at childhood was significantly and positively associated with changes in BMI (β=0.265; P=0.024), sum of five skinfolds (β=0.3445; P=0.003), body fat percentage (β=1.042; P=0.016) and waist circumference (β=0.806; P=0.002) from childhood to adolescence. These relationships persisted when overweight children were excluded from the analysis. BMI, sum of five skinfolds, body fat percentage and waist circumference at childhood were not significantly associated with changes in HOMA-IR (P for all >0.1).

CONCLUSIONS

These results give further support to the concept that lower insulin sensitivity at childhood may predict subsequent total and central adiposity gain at adolescence. These findings enhance the role of insulin sensitivity as a target of obesity prevention already from the first decades of life.

The effect of family-based multidisciplinary cognitive behavioral treatment in children with obesity: study protocol for a randomized controlled trial

BACKGROUND

The prevalence of childhood obesity has increased rapidly during the last three decades in the Netherlands. It is assumed that mainly environmental factors have contributed to this trend. Parental overweight and low social economic status are risk factors for childhood obesity. Childhood obesity affects self-esteem and has negative consequences on cognitive and social development. Obese children tend to become obese adults, which increases the risk for developing cardiovascular complications, type 2 diabetes mellitus, and psychosocial problems. Additionally, the secretion of several gastrointestinal hormones, responsible for appetite and food intake, is impaired in obese subjects. Weight reduction through lifestyle changes in order to change health risks is, until now, suggested as the preferred treatment for childhood obesity.The objective of this study is the effect evaluation of a family-based cognitive behavioral multidisciplinary lifestyle treatment. The intervention aims to establish long-term weight reduction and stabilization, reduction of obesity-related health consequences and improvement of self-image by change of lifestyle and learning cognitive behavioral techniques.

STUDY DESIGN/METHODS

In this randomized clinical trial newly presented children with obesity (8-17 years old) are divided, by randomization, in an intervention and control group, both consisting of 40 obese children. The intervention is carried out in groups of 8-11 children, and consists of respectively 7 and 5 separate group meetings for the children and their parents and 1 joint group meeting of 2 ½ hours. Main topics are education on nutrition, self-control techniques, social skills, physical activity and improvement of self-esteem. The control group is given advice on physical activity and nutrition. For normal data comparison, data were collected of 40 normal-weight children, 8-17 years old.

DISCUSSION

Because of the increasing prevalence of childhood obesity and the impact on the individual as well as on society, prevention and treatment of obesity in children is of great importance. For evaluation of short- and long-term effects of the treatment, measurements are taken before and after 3 months of treatment, and after 12 and 24 months follow-up. During these visits clinical and biochemical data are determined, cardiovascular fitness tests are performed and quality of life questionnaires are completed.

TRIAL REGISTRATION

International Standard Randomised Controlled Trial Number Register ISRCTN36146436

Changes in cardiorespiratory fitness predict changes in body composition from childhood to adolescence: findings from the European Youth Heart Study

BACKGROUND

Several variables, such as waist circumference (WC) and trunk skinfolds (TS), are indicators of body fat. There is interest in evaluating the effect of cardiorespiratory fitness (CRF) measures on changes in these markers from childhood to adolescence.

PURPOSE

To examine CRF as a potential predictor of changes in body fat over an 8-year follow-up period in a pediatric population.

METHODS

A cohort study of 86 children (44 girls, 42 boys) with a mean age of 9.8 ± 0.3 years who participated in the Portuguese arm of the European Youth Heart Study in 2000 completed a follow-up evaluation in 2008 at a mean age of 17.0 ± 0.4 years. Cardiorespiratory fitness, expressed as maximal oxygen consumption (VO2 max) (mL·kg(-1)·min(-1)), was assessed during an incremental multistage bicycle test to exhaustion. Physical activity (PA) was objectively measured by accelerometry at both periods of evaluation. Fat mass (FM) was assessed using anthropometric models, sum of TS, and WC. Changes were expressed as a percentage of the baseline value. Comparison of means and linear regression analysis were used for data analysis.

RESULTS

While CRF significantly increased among boys (P < 0.05) and decreased in girls (P < 0.01), the percentage of body fat decreased over time in boys (P < 0.01) and increased among girls. Alone, CRF explained 39%, 26%, and 25% of the total variance in WC, FM, and TS, respectively (P < 0.01). Adjusting for PA, sex, and maturation changes, CRF remained a significant predictor of WC (β = -0.335; P < 0.01), FM (β = -2.084; P < 0.01), and TS (β = -1.500; P < 0.01).

CONCLUSION

Changes in CRF are a significant predictor of changes in body fat percentage from childhood to adolescence. School-based PA interventions are encouraged to maintain or improve CRF from childhood and throughout adolescence to prevent increased percentages of body fat, particularly in the abdominal region.

[Cost-effectiveness of an intervention to reduce overweight and obesity in 9-10-year-olds. The Cuenca study]

OBJECTIVE

To assess the cost-effectiveness a school-based intervention designed to reduce overweight/obesity and other cardiovascular risk factors in children.

METHODS

Standard cost effectiveness analysis methods and two perspectives (societal and institutional) were used. A cluster-randomized controlled trial with 10 intervention schools (691 children) and 10 control schools (718 children) was performed. Net costs were calculated by subtracting the usual after-school care cost from intervention costs. The effectiveness of the intervention was measured as the reduction in health outcomes compared with the control group.

RESULTS

The intervention costs totaled 125,469.75€, representing 269.83 €/year/child. The usual after-school care was estimated at 844,56 €/year/child. Intervention children showed a decrease in triceps skinfold thickness (-1.25mm, 95% CI: -1.82 to -0.67; P<.001). Intervention children with body mass index (BMI) between the percentiles 25 and 75 showed a decrease in the percentage of body fat (-0.59%; 95% CI: -1.03 to -0.67; P<.001), and those with a BMI>P75 showed a decrease in triceps skinfold thickness (-1.87mm; 95%CI: -3.43 to -0.32; P<.001), and percentage of body fat (-0.67%; 95%CI: -1.32 to -0.01; P<.05).

CONCLUSIONS

This type of after-school program for recreational physical activity to prevent obesity are likely to be a cost-effective use of public funds and warrant careful consideration by policy makers and program planners.

Preliminary data on the association between waist circumference and insulin resistance in children without a previous diagnosis

The aim of the present work was to study the association between different anthropometric parameters and insulin resistance (IR) in Spanish schoolchildren without a previous diagnosis. A total of 443 Spanish schoolchildren (9-11 years of age) were studied in this cross-sectional study. The anthropometric measurements collected were weight, height, body circumferences and skinfolds. Body mass index (BMI), waist/hip ratio, percentage body fat and fat-free body mass were determined. Overnight-fasted blood lipids, insulin and glucose levels were analysed, and estimation of IR, taking into account the homeostasis model assessment (HOMA), was calculated. The children with IR had higher serum triglycerides and insulin levels, were heavier and taller, and had a higher BMI, a larger waist circumference, a larger hip circumference, a larger waist/hip ratio and thicker bicipital and tricipital skinfolds than those who did not have IR. Age, sex, BMI and waist circumference explained 32.0% of the variance in the HOMA values; only sex, triglycerides and waist circumference independently influenced this variable. A 1-cm increase in waist circumference was associated with approximately a 3.8% increase in the mean HOMA value. The children with a waist circumference of over the p90 for their age and sex were at greater risk of showing IR as measured by the HOMA: odds ratio = 6.94 (2.01-23.91; P < 0.001). In conclusion, according to these results, waist circumference is the best anthropometric parameter associated with IR in children, and those with a waist circumference of over the p90 for their age and sex would appear to be at particular risk.

Glucose metabolism and body composition in young adults treated with TBI during childhood

After SCT in childhood, survivors may develop disorders of glucose metabolism. The role of obesity is controversial. We measured insulin sensitivity using the homeostasis model assessment (HOMA) and the frequently sampled i.v. glucose tolerance test (FSIVGTT), as well as body composition using dual-energy X-ray absorptiometry in 18 young adults median 18.2 years after SCT and compared them with matched controls. We also measured growth hormone (GH) secretion, and levels of leptin and adiponectin. HOMA showed insulin resistance in eight patients (44%), as opposed to none of the controls (P=0.008) and FSIVGTT showed a decreased sensitivity index in the patients (2.98 vs 4.54 mU/L/min, P=0.042). Dual energy X-ray absorptiometry showed a higher percentage fat mass in the patients (34.9 vs 24.3%, P=0.011), which correlated inversely with the sensitivity index (r=-0.52, P=0.032). The patients had a lower peak value of GH (GH(max) 9 vs 20.7 mU/L, P=0.002). Time post SCT correlated with percentage fat mass and inversely with GH(max). The patients had higher levels of leptin and lower levels of adiponectin, even after adjustment for fat mass. We propose that the decreased insulin sensitivity may primarily be explained by the adverse body composition, which may owe to long-standing GH deficiency.

Adiposity, fitness and metabolic risk in children: a cross-sectional and longitudinal study

OBJECTIVE

To better understand the early development of cardiovascular disease, we examined the association of adiposity measures and cardiorespiratory fitness (CRF) with baseline values and changes in low-grade chronic inflammation and insulin resistance (IR) in school children.

METHODS

Eighty-three 1(st) and 5(th) grade children from a randomly selected control group of a physical activity intervention study (KISS) were prospectively studied during one academic year. Outcome variables included highly sensitive C-reactive protein (hs-CRP) and homeostasis assessment of IR (HOMA-IR). Adiposity measures included body mass index (BMI), waist circumference and the sum of skinfold thickness at four sites. CRF was assessed by the 20 m shuttle run test. All models were adjusted for age group, sex and pubertal group and included children who had a complete valid dataset for all variables.

RESULTS

Baseline metabolic markers correlated positively with measures of adiposity and inversely with CRF (all p ≤ 0.02). On average, longitudinal changes in hs-CRP concentration increased with high baseline BMI in boys and skinfold thickness in both genders (both p < 0.01). Increases in adiposity had an additional effect on these changes (adjusted R(2) of the models including baseline and change in adiposity 0.49-0.53, p < 0.001). On the other hand, longitudinal changes in HOMA-IR were positively related to changes in BMI and waist circumference (p ≤ 0.03). Increases in HOMA-IR, but not in hs-CRP concentrations, were associated with low baseline CRF (p = 0.01).

CONCLUSION

The relationship of baseline adiposity and CRF with increases in metabolic risk markers may have relevant implications for long-term cardiovascular risk. International Standard Randomised Controlled Trial Number (ISRCTN):

TRIAL REGISTRATION

isrctn.org 15360785.

Relationships of cardiorespiratory fitness with metabolic risk factors, inflammation, and liver transaminases in overweight youths

The aim of this study was to assess the relationships of fatness and fitness with metabolic risk factors, including liver transaminases and inflammation in obese youth, taking in account gender, age, and pubertal stage. 241 children were studied (135 girls), age 11.9 +/- 2.2 years (x +/- SD), Body Mass Index z score 5.4 +/- 2.7. For girls, VO(2max) was significantly associated with insulin (P = .001), Insulin resistance (HOMA-IR) (P = .005), and ALT (P = .012); a relationship was displayed between fibrinogen and age and % fat mass (FM) (P = .008); for boys, relationships were found between VO(2max) and diastolic blood pressure and triglycerides; independent associations were also found between age and insulin, HOMA-IR and HDL cholesterol; fibrinogen and sedimentation rate were related (P </= .004) with %FM. Their relationships are observed from young age and increase with the continuous increase of factors. This supports the need to treat overweight as soon as it is detected; improving CRF is one of the ways which could be used to prevent the complications of obesity.

Insulin resistance is a risk factor for high blood pressure regardless of body size and fat distribution in obese children

BACKGROUND AND AIM

The prevalence of children with hypertension is increasing, especially in obese children. This study was to assess the relationship between blood pressure, indexes of adiposity, body fat distribution and insulin resistance.

SAMPLE

1044 children (M/F: 484/560; aged 6-11 years). Anthropometry and blood pressure were measured and fasting blood samples were tested for triacylglycerol, total cholesterol, HDL cholesterol, glucose, insulin and ALT. The prevalence of high blood pressure in overweight males and females was 14.3 and 6.4%, respectively (chi(2)=16.73, p<0.001) and in obese it was 40.4 and 32.8%, respectively (chi(2)=5.56, p<0.001). High blood pressure increased progressively with BMI z-score categories (chi(2)=67.99, p<0.001) as well as with waist/height ratio (W/Hr) categories (chi(2)=23.51, p<0.001). Hypertensive subject had significantly higher insulin (15.6+/-9.8 vs 11.9+/-7.2, p<0.001 and 20.63+/-14.7 vs 15.26+/-9.8, p<0.001 in males and females respectively) and HOMA(IR) (3.23+/-2.1 vs 2.42+/-1.49, p<0.001 and 4.12+/-2.87 vs 3.07+/-1.98, p<0.001 in males and in females, respectively) than non-hypertensive ones. Among metabolic and cardiovascular risk factors, HOMA(IR) was the only variable able to predict high blood pressure in obese boys and girls, in addition to BMI or body fat distribution (waist, W/Hr). The highest HOMA(IR) category was the most important predicting factor of high blood pressure in overweight and obese children in addition to body size or body fat distribution.

CONCLUSIONS

Blood pressure is associated with the degree of overweight and the indices of body fat distribution. Insulin resistance is an independent additional risk factor for hypertension.

Fitness versus Fatness and Insulin Resistance in U.S. Adolescents

Background. The present study examined the relationship between insulin resistance and both waist circumference and cardiorespiratory fitness in U.S. adolescents. Methods. NHANES assessed a nationally representative sample of U.S. adolescents (12-18 yrs) between 1999-2002. Abdominal adiposity was estimated by waist circumference, overall adiposity by BMI, and cardiorespiratory fitness (maximal oxygen uptake (VO(2)max) from a treadmill exercise test). Insulin resistance was estimated from fasting insulin and glucose using the homeostatic model assessment method (i.e., HOMA) and was log-transformed. Results. 1078 adolescents were included in the study. Positive correlations existed between lnHOMA and waist circumference (r = 0.59; r = 0.54) for boys and girls, respectively. lnHOMA and VO(2)max were inversely related in boys (r = -0.29) but not girls (r = -0.06). Gender-specific analyses by BMI category showed that the significant inverse relationship in lnHOMA and VO(2)max was primarily present in obese boys. Conclusion. Among adolescents, important gender and BMI differences exist in the relationship between insulin resistance and fitness. While waist circumference and BMI are important predictors in all children, fitness appears especially important in obese boys. These findings may have important implications for gender-specific interventions to prevent adult obesity and diabetes mellitus.

Criterion-related validity of the one-mile run/walk test in children aged 8-17 years

We assessed the criterion-related validity of Cureton's equation for estimating peak oxygen consumption (VO(2peak)) from the one-mile run/walk test in endurance-trained children aged 8-17 years. Altogether, 66 physically active white children and adolescents (32 girls, 34 boys) completed a graded exercise test to volitional exhaustion and the one-mile run/walk test. Cureton's equation was used to estimate VO(2peak), and was assessed using several error measures. Agreement between measured VO(2peak) and estimated VO(2peak) was analysed by the Bland and Altman method. The correlation coefficient between measured VO(2peak) and one-mile run/walk time was -0.59 (P < 0.001) and that between measured and estimated VO(2peak) was 0.70 (P < 0.001). The mean difference between measured and estimated VO(2peak) was 10 ml . kg(-1) . min(-1) (95% CI = 9.2-11.8; P < 0.001). The standard error of the estimate was 3 ml . kg(-1) . min(-1), and the percentage error was 32%. There was a positive association between the measured and estimated VO(2peak) difference and the measured and estimated VO(2peak) mean, which indicates that the higher the VO(2peak) the higher the error of the estimate. These findings did not change markedly when the analyses were performed by sex, age group or body mass status. These results suggest that Cureton's equation systematically underestimates VO(2peak) in endurance-trained children with high VO(2peak).

High prevalence of cardio-metabolic risk factors among adolescents with intellectual disability

Adults with intellectual disabilities (IDs) have poor lifestyle-related health compared with the general population. Our aim was to study whether such differences are present already in adolescents.

AIM

To compare the prevalence and severity of cardio-metabolic risk factors and cardio-vascular fitness in adolescents with and without IDs.

METHODS

Intellectual disability (ID) students (n = 66) and non-intellectual disability (non-ID) students from practical (non-ID-p) (n = 34) and theoretical (non-ID-t) (n = 56) programmes were recruited from three upper secondary schools. Anthropometric data, blood pressure, body composition, fasting-insulin, fasting-glucose, fasting-lipids and cardio-vascular fitness were measured.

RESULTS

Participants with and without ID differed significantly in the prevalence of cardio-metabolic risk factors with participants with ID having a higher percentage of total fat mass, wider waist circumferences (WCs), lower levels of fat-free mass (FFM), lower bone mineral density (BMD) and higher insulin and homeostasis model assessment of insulin resistance (HOMA) levels and poorer cardio-vascular fitness. The healthiest levels were found in the non-ID-t group compared to the group with ID and the group with non-ID-p in between.

CONCLUSION

The prevalence of cardio-metabolic risk factors and poor cardio-vascular fitness was found to be high in this young population with intellectual disabilities. Measures should be taken to improve the health messages directed towards children and adolescents with intellectual disabilities.

Truncal and abdominal fat as determinants of high triglycerides and low HDL-cholesterol in adolescents

We examined whether abdominal and truncal adiposity, assessed with simple anthropometric indices, determines serum triglycerides and high-density lipoprotein (HDL)-cholesterol levels independently of total adiposity amount in adolescents. A total of 547 Spanish adolescents (284 males and 263 females) aged 13-18.5 years were included in this study. Measures of truncal adiposity included subscapular to triceps ratio, and trunk-to-total skinfolds ratio (TTS%). Waist circumference was used as a surrogate of abdominal adiposity, and BMI was used as a measure of total adiposity. The results of the regression models indicated that levels of triglycerides were positively associated with waist circumference and TTS% after controlling for age and Tanner stage in both sexes. Once BMI was entered in the model, these associations remained significant for waist circumference in females. HDL-cholesterol levels were negatively associated with waist circumference in both sexes, and with subscapular to triceps ratio and TTS% in males, after controlling for age and Tanner stage. Once BMI was entered in the model, these associations remained significant for subscapular to triceps ratio and for TTS% in males. The results of this study suggest that in male adolescents, truncal adiposity is negatively associated with levels of HDL-cholesterol, whereas in females, abdominal adiposity is positively associated with levels of triglycerides independently of total adiposity. These findings highlight the deleterious effect of both truncal and abdominal fat depots on the lipid profile already from the first decades of life.

Insulin sensitivity is correlated with subcutaneous but not visceral body fat in overweight and obese prepubertal children

AIM

Our aim was to explore the relationship between insulin sensitivity, body fat distribution, ectopic (liver and skeletal muscle) fat deposition, adipokines (leptin and adiponectin), and inflammation markers (highly sensitive C-reactive protein, IL-6, IL-10, and TNF-alpha) in prepubertal children.

SUBJECTS AND METHODS

Thirty overweight and obese children (16 males and 14 females with body mass index z-score range of 1.1-3.2) were recruited. Body fat distribution and fat accumulation in liver and skeletal muscle were measured using magnetic resonance imaging. Insulin sensitivity was assessed by iv glucose tolerance test.

RESULTS

Insulin sensitivity was associated with sc abdominal adipose tissue (SAT) (r = -0.52; P < 0.01) and liver fat content (r = -0.44; P < 0.02) but not with visceral abdominal adipose tissue (VAT) (r = -0.193; P value not significant) and fat accumulation in skeletal muscle (r = -0.210; P value not significant). Adipokines, but not inflammation markers, were significantly correlated to insulin sensitivity. VAT correlated with C-reactive protein (r = 0.55; P < 0.01) as well as adiponectin (r = -0.53; P <0.01). Multiple regression analysis showed that only SAT and liver fat content were independently correlated to insulin sensitivity (P < 0.01; 20 and 16% of explained variance, respectively).

CONCLUSIONS

In overweight and moderately obese prepubertal children, insulin sensitivity was negatively correlated with SAT and liver fat content. Furthermore, contrary to adults, VAT and inflammation markers were not correlated with insulin sensitivity in children.

Associations between physical activity, body fat, and insulin resistance (homeostasis model assessment) in adolescents: the European Youth Heart Study

BACKGROUND

More and better data are needed to understand the action of physical activity (PA) on insulin resistance and the concomitant relation with body fat in adolescence.

OBJECTIVE

We examined the relation between total PA and intensity levels with insulin resistance under special consideration of waist circumference and skinfold thickness.

DESIGN

This was a cross-sectional study of 613 adolescents (352 girls, 261 boys) with a mean (+/-SD) age of 15.5 +/- 0.5 y from Sweden and Estonia. Total, low, moderate, and vigorous PA was measured by accelerometry. Body fat estimators included waist circumference and the sum of 5 skinfold thicknesses. Fasting insulin and glucose were measured, and insulin resistance was calculated according to the homeostasis model assessment (HOMA). Linear regression analysis and analysis of covariance were used to determine the association between PA and insulin resistance while considering body fat. All estimates were adjusted for sex, country, pubertal status, and indicators of body fat when applicable.

RESULTS

Total, moderate, and vigorous PA were inversely correlated with HOMA. Body fat estimators were positively correlated with HOMA. Significant contrasts in HOMA concentrations were seen when comparing the lower 2 tertiles with the upper tertile of PA indicators. Repeating the analysis with body fat estimators showed significant contrasts in HOMA concentrations when comparing the lower tertiles with the upper tertile.

CONCLUSION

In view of an increase in obesity in young people, the results accentuate the role of PA in sustaining metabolic balance in adolescence and the potential benefit of an increase of time spent at higher PA levels for youth with relatively elevated amounts of body fat.