Season, Terrestrial Ultraviolet Radiation, and Markers of Glucose Metabolism in Children Living in Perth, Western Australia.

Seasonality in glucose metabolism has been observed in adult populations; however, little is known of the associations between season and glucose metabolism in children. In this study, we examined whether markers of glucose metabolism (fasting glucose, insulin and HbA1c) varied by season in a paediatric population (6-13 years of age) located in Perth (Western Australia, n = 262) with data categorised by weight. Linear regression was used to analyse the nature of the relationships between mean daily levels of terrestrial ultraviolet radiation (UVR) (prior to the day of the blood test) and measures of glucose metabolism. Fasting blood glucose was significantly lower in autumn compared to spring, for children in combined, normal and obese weight categories. Fasting insulin was significantly lower in autumn and summer compared to winter for individuals of normal weight. HbA1c was significantly higher in summer (compared with winter and spring) in overweight children, which was in the opposite direction to other published findings in adults. In children with obesity, a strong inverse relationship (r = -0.67, p = 0.002) was observed for fasting glucose, and daily terrestrial UVR levels measured in the previous 6 months. Increased safe sun exposure in winter therefore represents a plausible means of reducing fasting blood sugar in children with obesity. However, further studies, using larger paediatric cohorts are required to confirm these relationships.

Body mass index and waist circumference: relationship to cardiometabolic risk factors in children--Busselton Health Study 2005-2007.

AIM: This study aims to analyse the continuous relationship of each cardiometabolic risk factor with body mass index (BMI) and waist circumference percentiles in a population-based sample of children. METHODS: A cross-sectional sample of 996 school children aged 6-16.9 years in Busselton, Western Australia, (2005-2007) had anthropometry and fasting blood tests for total cholesterol, high density lipoprotein, low density lipoprotein, triglycerides, glucose, insulin, high-sensitive C-reactive protein, liver function tests and adiponectin. Age- and menarche (for girls)-adjusted means of each risk factor were related to BMI and waist circumference centiles across the full normal-overweight-obese range. RESULTS: The correlations between BMI and waist circumference (boys 0.91 and girls 0.91) and between BMI z-score and waist z-score (boys 0.80 and girls 0.82) were high. An increase in insulin across all centile groups (for BMI and waist circumference) was found in both sexes. An increase was found for diastolic blood pressure and systolic blood pressure z-score, high density lipoprotein, high-sensitive C-reactive protein, alanine transaminase and gamma-glutamyltransferase in only the centile groups >85% for BMI and waist circumference for both sexes. Mixed and sex-discordant results were found for triglycerides, adiponectin and glucose. CONCLUSION: There are important differences in the relationships between increasing BMI/adiposity, and each comorbidity and these relationships can differ between boys and girls. This information has implications for screening and management of adiposity-related cardiometabolic risk factors in children and for public health initiatives to reduce future burden of cardiovascular disease.

Lipids in Australian children: cause for concern? 2005-2007 Busselton Health Study.

AIM: To report the current lipid status of Australian school children from a population-based sample and compare this to international and Australian data. METHODS: A cross section of school children aged 6 to 16.9 years in Busselton, Western Australia (WA) between 2005 and 2007 had fasting lipids tested. The first analysis compares the Busselton sample to data recommended by the American Academy of Paediatrics (AAP) 2008. The second analysis compares the Busselton sample to data from the Schools Physical Activity and Nutrition Survey (SPANS) study, New South Wales (NSW), Australia, 2004 and the 1985 Australian Health and Fitness Survey (AHFS). The third analysis applies laboratory-reported cut-points in WA to report percentages over 'healthy desirable norms'. RESULTS: Analysis 1: higher levels of total cholesterol and triglycerides in Busselton children compared to AAP data source. Boys had higher low-density lipoprotein (LDL) levels. Analysis 2: comparable rates of dyslipidaemia to SPANS 2004 but lower rates compared to the AHFS, 1985. Analysis 3: total and LDL-cholesterol above recommended range in 32.7% and 19.4% of boys and 38.2% and 24.6% of girls. CONCLUSION: In a large population-based sample of Australian school children, we found a higher frequency of abnormal lipid profiles when compared to American data. In addition, many children have levels outside reported healthy norms for Australian children. Research tracking lipid profiles of Australian children into adulthood is needed to understand the association of these levels with future cardiovascular risk.

High incidence of obesity co-morbidities in young children: a cross-sectional study.

AIM: The prevalence of overweight and obesity in children is a public health problem because of future morbidity. However, the prevalence of medical complications in overweight and obese primary school children in Australia is not well documented. As part of the larger, prospective cohort Growth and Development Study, this report aimed to identify the medical complications of obesity in a population-based community sample of primary school-aged children. METHODS: Two groups of primary school children were studied: a random community sample of overweight/obese children (not seeking treatment) and a matched community sample of normal weight children. Demographics, medical history, family history and symptoms of complications of overweight were collected. Children had a physical examination, oral glucose tolerance tests with insulins, fasting lipid profiles and liver function tests. RESULTS: Data from 283 children are presented (6.1-13.4 years, mean 9.8 years). There were no differences in birth data, family composition, parental age or socio-economic status between groups. Overweight and obese children were more likely to complain of musculoskeletal pain, depression, anxiety and bullying, and had more adverse examination findings than control children. They also had more abnormal investigations: overweight children: impaired glucose tolerance (IGT) 1.3%, hyperinsulinism 19.5%, dyslipidaemia 63.8%, raised alanine transaminase (ALT) 9.0%; obese children: IGT 5.3%, hyperinsulinism 38.9%, dyslipidaemia 73.7%, raised ALT 31.6%. CONCLUSION: Overweight and obese primary school-aged children have significant medical complications of their weight status. Overweight children, in addition to obese children, should be screened for complications. A secondary finding is a high proportion of normal weight children with lipid levels outside desirable healthy ranges.

Waist circumference predicts cardiovascular risk in young Australian children.

AIM: It has been shown that compared with healthyweight children, overweight and obese primary school-aged children have a higher incidence of hyperinsulinism, dyslipidaemia and hypertension. It is therefore important to investigate clinically relevant markers of cardiovascular risk in children. Waist circumference is a simple, non-invasive anthropometric measure, but its association with cardiovascular risk profile in young Australian children is not clear. METHODS: This study presents cross-sectional data from the Growth and Development Study. The sample included 70 healthy weight children, 50 overweight children and 28 obese children (n = 148, 9.6 +/- 1.9 years). All children had a medical assessment which included a physical examination (waist circumference, blood pressure), and investigations including glycated haemoglobin, total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, insulin, glucose and total homocysteine levels. An oral glucose tolerance test was performed in a subgroup of children (n = 119). Body mass index (BMI) was determined and BMI Z-scores calculated. RESULTS: In a multilevel model, waist circumference was the only significant anthropometric predictor of lipid profile (high-density lipoprotein beta = -0.01, P < 0.05; triglycerides beta = 0.01, P < 0.005), systolic blood pressure (beta = 0.29, P < 0.05), fasting insulin (beta = 0.16, P < 0.005), insulin concentrations throughout the oral glucose tolerance (60 min beta = 1.07, P < 0.005; 120 min beta = 1.42, P < 0.001) and insulin resistance (homeostasis model assessment (HOMA-IR): beta = 0.03, P < 0.05), with increasing waist circumference associated with increasing cardiovascular risk. In contrast, BMI Z-score was only predictive of 120-min glucose concentrations during the OGTT (beta = 0.34, P < 0.05). CONCLUSIONS: Waist circumference is a better anthropometric indicator than BMI Z-score of cardiovascular risk in Australian primary school-aged children. Even in young children, measurement of waist circumference represents a simple, non-invasive screening tool to identify children with an increased cardiovascular risk profile.

Exercise alone reduces insulin resistance in obese children independently of changes in body composition.

CONTEXT: The number of obese children with insulin resistance and type 2 diabetes is increasing, but the best management strategy is not clear. OBJECTIVE: The objective of this study was to assess the effect of a structured 8-wk exercise training program on insulin resistance and changes in body composition in obese children. DESIGN: The study was 8 wk of structured supervised exercise intervention with outcome measures before and after the exercise period. SUBJECTS: Fourteen obese children (12.70 +/- 2.32 yr; eight male, six female) with high fasting insulin levels were enrolled into the study. INTERVENTION: INTERVENTION consisted of 8 wk of supervised circuit-based exercise training, composed of three fully supervised 1-h sessions per week. OUTCOME MEASURES: Outcome measures were assessed pretraining program and posttraining program and included insulin sensitivity (euglycemic-hyperinsulinemic clamp studies), fasting insulin and glucose levels, body composition using dual energy x-ray absorptiometry scan, lipid profile, and liver function tests. RESULTS: Insulin sensitivity improved significantly after 8 wk of training (M(lbm) 8.20 +/- 3.44 to 10.03 +/- 4.33 mg/kg.min, P < 0.05). Submaximal exercise heart rate responses were significantly lower following the training (P < 0.05), indicating an improvement in cardiorespiratory fitness. Dual energy x-ray absorptiometry scans revealed no differences in lean body mass or abdominal fat mass. CONCLUSION: An 8-wk exercise training program increases insulin sensitivity in obese children, and this improvement occurred in the presence of increased cardiorespiratory fitness but is independent of measurable changes in body composition.

Increasing body mass index z-score is continuously associated with complications of overweight in children, even in the healthy weight range.

CONTEXT: Overweight/obesity in children is increasing. Incidence data for medical complications use arbitrary cutoff values for categories of overweight and obesity. Continuous relationships are seldom reported. OBJECTIVES: The objective of this study is to report relationships of child body mass index (BMI) z-score as a continuous variable with the medical complications of overweight. DESIGN: This study is a part of the larger, prospective cohort Growth and Development Study. SETTING: Children were recruited from the community through randomly selected primary schools. Overweight children seeking treatment were recruited through tertiary centers. PARTICIPANTS: Children aged 6-13 yr were community-recruited normal weight (n = 73), community-recruited overweight (n = 53), and overweight treatment-seeking (n = 51). Medical history, family history, and symptoms of complications of overweight were collected by interview, and physical examination was performed. Investigations included oral glucose tolerance tests, fasting lipids, and liver function tests. MAIN OUTCOME MEASURE: Adjusted regression was used to model each complication of obesity with age- and sex-specific child BMI z-scores entered as a continuous dependent variable. RESULTS: Adjusted logistic regression showed the proportion of children with musculoskeletal pain, obstructive sleep apnea symptoms, headaches, depression, anxiety, bullying, and acanthosis nigricans increased with child BMI z-score. Adjusted linear regression showed BMI z-score was significantly related to systolic and diastolic blood pressure, insulin during oral glucose tolerance test, total cholesterol, high-density lipoprotein, triglycerides, and alanine aminotransferase. CONCLUSION: Child's BMI z-score is independently related to complications of overweight and obesity in a linear or curvilinear fashion. Children's risks of most complications increase across the entire range of BMI values and are not defined by thresholds.

Do skinfolds accurately assess changes in body fat in obese children and adolescents?

PURPOSE: Obesity is epidemic in Western societies, with rapid rates of increase in the young. Various methods exist for the assessment of body composition, but these have not been compared in obese children and adolescents. This study compared methods of body composition assessment in obese young people to determine whether changes in various measures of body composition as a result of exercise training were correlated. METHODS: Multiple anthropometric measures (weight, height, body mass index (BMI), skinfolds, waist and hip girths) and dual-energy x-ray absorptiometry (DEXA) were undertaken in 38 obese children and adolescents (12.7 +/- 2.1 yr) at baseline and following 8 wk of exercise training. RESULTS: At baseline, there were strong relationships (all P < 0.01) between DEXA total fat and weight (r = 0.83), BMI (r = 0.86), waist girth (r = 0.81), hip girth (r = 0.88), sum of six skinfolds (sum6, r = 0.79), and percent body fat (percent body fat) calculated using a four-skinfold equation (EQ4; r = 0.69). Similar relationships (all P < 0.001) existed between DEXA abdominal fat and weight (r = 0.79), waist girth (r = 0.83), hip girth (r = 0.69), and height (r = 0.71). Neither skinfold sums, nor percent body fat calculated from skinfold equations, were selected as independent predictors of DEXA total or abdominal fat by stepwise hierarchical linear regression. The reductions in DEXA total and abdominal fat following exercise were not predicted by changes in skinfolds or percent body fat calculated from skinfolds. CONCLUSION: These data suggest that body fat derived from skinfold measures is poorly predictive of abdominal and total fat derived from DEXA in obese children and adolescents. This finding highlights the limitations of skinfolds in obese subjects and questions the validity of their use to assess changes in body composition with interventions such as exercise training.