30-year cross-sectional trends in waist-to-height ratio in Australian school age children; 1985 to 2015

AIM

To report 30-year changes in the proportion of children with abdominal obesity measured by waist-to-height ratio (WHtR) ≥ 0.5.

METHODS

Secondary analysis of WHtR ≥ 0.5 data on Australian children age 7 to 15 years from five national cross-sectional population surveys conducted in 1985, 1995, 2007, 2012 and 2015. Changes in the proportions of children with a WHtR ≥ 0.5 across survey years, by age and sex were assessed using chi-squared tests.

RESULTS

Between 1985 and 2012, the proportion of children with WHtR ≥ 0.5 increased from 8.6% [95%CI: 8.0, 9.2] to 25.1% [95%CI: 23.5, 26.7]. An increase of ~5% each decade was observed between 1985 and 2007, and a 6.6% increase was observed between 2007 and 2012. Overall, there was a non-significant decrease in the proportion of children with WHtR ≥ 0.5 between 2012 (25.1% [95%CI: 23.5, 26.7] and 2015 (23.3% [95%CI: 21.6, 25.2].

CONCLUSION

Abdominal obesity has increased over the last 30 years in Australian children. In 2015, one in five children had WHtR ≥ 0.5, a marker of cardiometabolic risk in children. Our finding highlights the importance of including WHtR as a routine measurement in primary health care and population health surveys. This information is needed to guide policy and practice to manage long-term cardiovascular risk in children.

Australasian nutrition research for prevention and management of child obesity: innovation and progress in the last decade

BACKGROUND/OBJECTIVE

The Food and Nutrition stream of Australasian Child and Adolescent Obesity Research Network (ACAORN) aims to improve the quality of dietary methodologies and the reporting of dietary intake within Australasian child obesity research (http://www.acaorn.org.au/streams/nutrition/).

METHODS/RESULTS

With 2012 marking ACAORN's 10th anniversary, this commentary profiles a selection of child obesity nutrition research published over the last decade by Food and Nutrition Stream members. In addition, stream activities have included the development of an online selection guide to assist researchers in their selection of appropriate dietary intake methodologies (http://www.acaorn.org.au/streams/nutrition/dietary-intake/index.php).

CONCLUSIONS

The quantity and quality of research to guide effective child obesity prevention and treatment has increased substantially over the last decade. ACAORN provides a successful case study of how research networks can provide a collegial atmosphere to foster and coordinate research efforts in an otherwise competitive environment.

Waist-to-height ratio and cardiometabolic risk factors in adolescence: findings from a prospective birth cohort

OBJECTIVE

To examine the associations between body mass index (BMI) and waist-to-height ratio (WHtR) measured in childhood and adolescence and cardiometabolic risk factors in adolescence.

METHODS

Secondary data analysis of the Avon Longitudinal Study of Parents and Children, a population based cohort. Data from 2858 adolescents aged 15.5 (standard deviation 0.4) years and 2710 of these participants as children aged 7-9 years were used in this analysis. Outcome measures were cardiometabolic risk factors, including triglycerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol, insulin, glucose and blood pressure at 15 years of age.

RESULTS

Both BMI and WHtR measured at ages 7-9 years and at age 15 years were associated with cardiometabolic risk factors in adolescents. A WHtR ≥0.5 at 7-9 years increased the odds by 4.6 [95% confidence interval 2.6 to 8.1] for males and 1.6 [0.7 to 3.9] for females of having three or more cardiometabolic risk factors in adolescence. Cross-sectional analysis indicated that adolescents who had a WHtR ≥0.5, the odds ratio of having three or more cardiometabolic risk factors was 6.8 [4.4 to 10.6] for males and 3.8 [2.3 to 6.3] for females. The WHtR cut-point was highly specific in identifying cardiometabolic risk co-occurrence in male children and adolescents as well as female children (90 to 95%), but had poor sensitivity (17 to 53%). Similar associations were observed when BMI was used to define excess adiposity.

CONCLUSIONS

WHtR is a simple alternative to age and sex adjusted BMI for assessing cardiometabolic risk in adolescents.

The prevalence of increased central adiposity in Australian school children 1985 to 2007

The epidemic of obesity as measured by body mass index (BMI) maybe plateauing. However, studies using skin-fold and waist circumference measurements suggest that BMI may underestimate changes in fatness in children. In this study we examine changes in waist circumference and waist-to-height ratio (WHtR) in Australian children between 1985 and 2007, by undertaking secondary data analysis of three national data sets. The mean waist circumference z-score for boys increased from -0.02 (95% CI -0.05 to 0.01) in 1985, to 0.33 (0.26 to 0.40) in 1995 and 0.41 (0.35 to 0.47) in 2007 and was greater (P<0.001) than the increase in BMI z-score. The increase in mean waist circumference z-score for girls was greater (P<0.001) than boys and increased from -0.02 (0.05 to 0.01) in 1985, to 0.33 (0.26 to 0.41) in 1995 and to 0.57 (0.51 to 0.63) in 2007. The number of children with a WHtR ≥ 0.5 increased from 8.6% in 1985, to 13.6% in 1995 and 18.3% in 2007. Between 1985 and 2007 central adiposity increased at a faster rate than total adiposity, particularly in girls. The secular increase in waist circumference and WHtR is concerning as measures of central adiposity are associated with metabolic and cardiovascular risk.

Treatment of clinical insulin resistance in children: a systematic review

The objective of this study was to evaluate the effectiveness of interventions aimed at improving clinical insulin resistance and/or pre-diabetes in children. This study is a systematic review and meta-analysis. Five electronic databases were searched for randomized controlled trials of at least 2-months' duration. The outcomes were fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), body mass index (BMI) and adverse outcomes. Four randomized controlled trials were identified. All compared the effect of 6 months of metformin plus or minus lifestyle intervention with placebo plus or minus lifestyle intervention. After pooling results from three trials, the mean difference after 6 months favoured the intervention with a statistically significant mean decrease in fasting insulin, HOMA-IR and BMI of 9.6 µU mL(-1) (95% confidence interval [CI]: 6.3, 13.0 µU mL(-1) ; I(2) = 76%), 2.7 (95% CI: 1.7, 3.6; I(2) = 74%) and 1.7 kg m(-2) (95% CI: 1.1, 2.3 kg m(-2) ; I(2) = 75) respectively. Mild gastrointestinal symptoms were reported in 19% (2-29%; median and range) of participants taking metformin. Metformin improves markers of insulin sensitivity and reduces BMI in children and adolescents with clinical insulin resistance or pre-diabetes. Stronger evidence from high-quality studies of longer duration and larger sample size are required before clinical conclusions about the optimal treatment protocol in this population can be drawn.

Waist-to-height ratio: a simple option for determining excess central adiposity in young people

Waist circumference is recommended as a means of identifying people at risk of morbidity associated with central adiposity. Yet, there are no universally agreed cut-points to determine when a waist circumference is too large in young people. In this study we examined the relation between sex- and age-specific waist circumference cut-points, the waist-to-height ratio (WHtR) cut-point of <0.5 and cardiovascular disease (CVD) risk clustering in 164 young people, mean age 14.9+/-0.2 years (mean+/-s.d.). In total 19 (11.6%) of the sample were identified as having CVD risk clustering. These young people were significantly (P<0.001) heavier and had higher body mass index (BMI) and waist circumference z-scores compared to those without CVD risk clustering. The WHtR cut-point of 0.5 estimated CVD risk clustering to a similar extent to sex- and age-adjusted cut-points for waist circumference and BMI. Young people with excess central adiposity (WHtR> or =0.5) were 11 times (OR 11.4, P<0.001), more likely to have CVD risk clustering compared to those who did not have excess central adiposity. The WHtR has several advantages; it is easy to calculate, does not require sex- and age-specific centiles and as has been previously suggested, it is a simple message, easily understood by clinicians and families, to 'keep your waist circumference to less than half your height'.

Soft drink consumption and excess weight gain in Australian school students: results from the Nepean study

We studied the relation between soft drink/cordial (a sweet, flavoured, concentrated syrup that is mixed with water to taste), fruit juice/drink and milk consumption in mid-childhood, and body mass index (BMI) status in early adolescence in a contemporary Australian cohort. In 1996/7, 268 children (136 males) were recruited from western Sydney at baseline (mean+/-s.d.: 7.7+/-0.6 years), and at follow-up 5 years later (13.0+/-0.2 years). Height and weight were measured at both time periods and overweight and obesity defined using the International Obesity TaskForce criteria. Beverage consumption was calculated from a 3-day food record at baseline. Median carbohydrate intake from soft drink/cordial was 10 g higher (P=0.002) per day in children who were overweight/obese at follow-up compared to those who had an acceptable BMI at both baseline and follow-up. Intakes of soft drink/cordial in mid-childhood, but not fruit juice/fruit drink and milk, were associated with excess weight gain in early adolescence.

Increasing central adiposity: the Nepean longitudinal study of young people aged 7–8 to 12–13 y

BACKGROUND

Estimates of the prevalence of overweight and obesity in young people are typically based on body mass index (BMI). However, BMI may not indicate the level of central adiposity. Waist circumference has therefore been recommended to identify young people at risk of morbidity associated with central adiposity.

OBJECTIVE

To investigate (a) change in total and central adiposity between 7-8 and 12-13 y (b) agreement between classifying young people as overweight or obese based on total adiposity and central adiposity, and (c) risk factors associated with the development of total and central adiposity.

DESIGN

Anthropometric measurements were taken on 342 children in 1996/97 and 5 y later. Risk factors examined included birth weight, physical activity, TV viewing, pubertal status, parental adiposity, diet and socio-economic status.

RESULTS

Between 7-8 and 12-13 y indices of central adiposity increased more than total adiposity; waist circumference z-score increased by (mean+/-s.d.) 0.74+/-0.92 and BMI z-score increased by 0.18+/-0.67. At 12-13 y there was moderate agreement between the two measures of adiposity (weighted kappa=0.64). However, waist circumference identified a greater number of young people as overweight or obese compared to BMI (41.2 vs 29.3%, P<0.001). Adiposity status at 7-8 y, maternal obesity, and pubertal stage were the strongest predictors of BMI status at 12-13 y. Risk factors associated with increased central adiposity were similar.

CONCLUSIONS

Overweight and obesity, as measured by waist circumference, is a bigger problem than is currently assessed by BMI. Targeting known risk factors for total adiposity may be an appropriate strategy for preventing increased central adiposity.

Features of the metabolic syndrome after childhood craniopharyngioma

Obesity and multiple pituitary hormone deficiency are common complications after surgery for childhood craniopharyngioma. We hypothesized that post craniopharyngioma surgery, children are at high risk for the metabolic syndrome, including insulin resistance due to excess weight gain and GH deficiency. This study characterized body composition (anthropometry and dual energy x-ray absorptiometry) and metabolic outcomes in 15 children (10 males and 5 females; age, 12.2 yr; range, 7.2-18.5 yr) after surgical removal of craniopharyngioma. In 9 subjects, outcomes were compared with those of healthy age-, sex-, body mass index-, and pubertal stage-matched controls. Insulin sensitivity was measured by 40-min iv glucose tolerance test. Seventy-three percent of subjects were overweight or obese. Sixty-six percent had normal growth velocity without GH treatment. Subjects had increased abdominal adiposity (P = 0.008) compared with controls. However, there was no significant difference in total body fat. Subjects had higher fasting triglycerides (P = 0.02) and lower high density lipoprotein cholesterol to total cholesterol ratio (P = 0.015). Insulin sensitivity was equally reduced for subjects and controls (P = 0.86). After craniopharyngioma removal, patients had more features of the metabolic syndrome compared with controls. This could be a result of hypothalamic damage causing obesity and GH deficiency. Further studies exploring predictors of the metabolic syndrome after craniopharyngioma surgery are required.

Abdominal fat and birth size in healthy prepubertal children

BACKGROUND

Studies examining the foetal origins hypothesis suggest that small birth size may be a marker of foetal adaptations that programme future propensity to adult disease. We explore the hypothesis that birth size may relate to fat distribution in childhood and that fat distribution may be a link between birth size and adult disease.

OBJECTIVE

To investigate the relationship between birth size and abdominal fat, blood pressure, lipids, insulin and insulin:glucose ratio in prepubertal children.

DESIGN

Cross-sectional study, based on a birth cohort of consecutive full-term births.

SUBJECTS

Two hundred and fifty-five (137 females) healthy, 7- and 8-y-old children.

MEASUREMENTS

Body composition and abdominal fat was measured by dual energy X-ray absorptiometry. Lipid, glucose and insulin profiles were measured after an overnight fast and an automated BP monitor was used for blood pressure measurements.

RESULTS

There was a negative association between abdominal fat and birth weight s.d. score across a range of normal birth weights (beta=-0.18; 95% CI=-0.31 to -0.04, P=0.009) and a positive association with weight s.d. score at 7/8 y (beta=0.35; 95% CI=0.24 to 0.46, P<0.001). Children who were born with the lowest weight s.d. score and had the greatest weight s.d. score at 7/8 y had significantly more (P<0.001) abdominal fat, as a percentage of total fat (6.53+/-1.3%) than those who had the highest birth weight s.d. score and the lowest weight s.d. score at 7/8 y (4.14+/-0.5%). Similar results were seen if head circumference, but not ponderal index, was used as an indicator of birth size. Increased abdominal fat was associated with higher total cholesterol:HDL cholesterol, higher triglyceride concentration and increased diastolic blood pressure.

CONCLUSIONS

Birth weight independently predicted abdominal fat. Children with the highest amount of abdominal fat were those who tended to be born lighter and gained weight centiles. Increased abdominal fat was associated with precursor risk factors for ischaemic heart disease.

Initial characterization of the GH-IGF axis and nutritional status of the Ati Negritos of the Philippines

BACKGROUND AND OBJECTIVE

The Ati Negritos are a Pygmy-like aboriginal population from the Philippines with physical characteristics of short stature, dark skin and woolly, kinked hair. Their final height, components of their GH-IGF axis and various nutritional markers are described. SUBJECTS, DESIGN AND MEASUREMENTS: Auxological data and sera for the components of the GH-IGF axis and nutritional parameters were collected from 9 adult Ati Negritos in their native environment and 10 Filipinos in Sydney.

RESULTS

The height SDS (- 3.66 +/- 1.1 vs. - 1.01 +/- 1.2), weight SDS (- 2.30 +/- 1.6 vs. 0.10 +/- 0.7), and BMI SDS (- 1.4 +/- 1.8 vs. - 0.2 +/- 0.5) between the two groups were significantly different (P < 0.01). The mean height of the 6 male Ati Negritos was 149 +/- 7 and 144 +/- 3 cm for the females and are comparable with the African Pygmies and the Mountain Ok people of Papua New Guinea. The Ati Negritos showed lower growth hormone binding protein (GHBP), insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 3 (IGFBP-3), acid labile subunit (ALS), zinc, albumin, ferritin, iron, iron saturation and much higher insulin-like growth factor binding protein 2 (IGFBP-2) and plasma transferrin concentrations. No differences were noted in random growth hormone (GH), plasma insulin-like growth factor II (IGF-II), nor in their plasma concentrations of prealbumin, thyroid stimulating hormone (TSH) and free thyroxine (T4).

CONCLUSION

Perturbations of both the GH-IGF-I axis and nutritional markers exist in the Ati Negritos. These findings may be determinants of their stature; however, the aetiology of these changes remains to be fully elucidated.

Nutrition in early life: somatic growth and serum lipids

This paper addresses the questions of whether early nutritional experience affects later somatic growth, the growth of the adipose tissue, or the levels of serum lipids among well-nourished children. The analyses are based on data from three prospective studies. Postnatal nutrition and growth: there were differences in growth between breast-fed and formula-fed children. There was no association between linear growth and differences in food energy or macronutrient intake. Birth size and postnatal growth: there was no association between ponderal index (PI) at birth and body mass index (BMI) in the second year. For boys, the PI at 3 and 6 months of age was significantly positively correlated with BMI at the ages of 8 and 15 years, but not for girls. Childhood growth and lipids: there was no association between lipids at the age of 8 years and either birth weight or length, but children who had had a low PI at birth had higher lipid levels at the age 8 years. A positive association was found between serum lipids and abdominal fat and BMI. We conclude that, although early diet may influence growth rate beyond infancy, the evidence for fat patterning resulting from differences in fetal or early postnatal nutrition is still open to question.