Characterizing extreme values of body mass index-for-age by using the 2000 Centers for Disease Control and Prevention growth charts
ABSTRACT The 2000 Centers for Disease Control and Prevention (CDC) growth charts included lambda-mu-sigma (LMS) parameters intended to calculate smoothed percentiles from only the 3rd to the 97th percentile.
The objective was to evaluate different approaches to describing more extreme values of body mass index (BMI)-for-age by using simple functions of the CDC growth charts.
Empirical data for the 99th and the 1st percentiles of BMI-for-age were calculated from the data set used to construct the growth charts and were compared with estimates extrapolated from the CDC-supplied LMS parameters and to various functions of other smoothed percentiles. A set of reestimated LMS parameters that incorporated a smoothed 99th percentile were also evaluated.
Extreme percentiles extrapolated from the CDC-supplied LMS parameters did not match well to the empirical data for the 99th percentile. A better fit to the empirical data was obtained by using 120% of the smoothed 95th percentile. The empirical first percentile was reasonably well approximated by extrapolations from the LMS values. The reestimated LMS parameters had several drawbacks and no clear advantages.
Several approximations can be used to describe extreme high values of BMI-for-age with the use of the CDC growth charts. Extrapolation from the CDC-supplied LMS parameters does not provide a good fit to the empirical 99th percentile values. Simple approximations to high values as percentages of the existing smoothed percentiles have some practical advantages over imputation of very high percentiles. The expression of high BMI values as a percentage of the 95th percentile can provide a flexible approach to describing and tracking heavier children.
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ABSTRACT: The epidemic of overweight and obesity presents a major challenge to chronic disease prevention and health across the life course around the world. Fueled by economic growth, industrialization, mechanized transport, urbanization, an increasingly sedentary lifestyle, and a nutritional transition to processed foods and high-calorie diets over the last 30 years, many countries have witnessed the prevalence of obesity in its citizens double and even quadruple. A rising prevalence of childhood obesity, in particular, forebodes a staggering burden of disease in individuals and healthcare systems in the decades to come. A complex, multifactorial disease, with genetic, behavioral, socioeconomic, and environmental origins, obesity raises the risk of debilitating morbidity and mortality. Relying primarily on epidemiologic evidence published within the last decade, this non-exhaustive review discusses the extent of the obesity epidemic, its risk factors-known and novel-, sequelae, and economic impact across the globe.PharmacoEconomics 12/2014; DOI:10.1007/s40273-014-0243-x · 3.34 Impact Factor
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ABSTRACT: BackgroundA higher protein to carbohydrate ratio in the diet may potentiate weight loss, improve body composition and cardiometabolic risk, including glucose homeostasis in adults. The aim of this randomised control trial was to determine the efficacy of two structured lifestyle interventions, differing in dietary macronutrient content, on insulin sensitivity and body composition in adolescents. We hypothesised that a moderate-carbohydrate (40-45% of energy), increased-protein (25-30%) diet would be more effective than a high-carbohydrate diet (55-60%), moderate-protein (15%) diet in improving outcomes in obese, insulin resistant adolescents.Methods Obese 10¿17 year olds with either pre-diabetes and/or clinical features of insulin resistance were recruited at two hospitals in Sydney, Australia. At baseline adolescents were prescribed metformin and randomised to one of two energy restricted diets. The intervention included regular contact with the dietician and a supervised physical activity program. Outcomes included insulin sensitivity index measured by an oral glucose tolerance test and body composition measured by dual-energy x-ray absorptiometry at 12 months.ResultsOf the 111 adolescents recruited, 85 (77%) completed the intervention. BMI expressed as a percentage of the 95th percentile decreased by 6.8% [95%CI: ¿8.8 to ¿4.9], ISI increased by 0.2 [95%CI: 0.06 to 0.39] and percent body fat decreased by 2.4% [95%CI: ¿3.4 to ¿1.3]. There were no significant differences in outcomes between diet groups at any time.Conclusion When treated with metformin and an exercise program, a structured, reduced energy diet, which is either high-carbohydrate or moderate-carbohydrate with increased-protein, can achieve clinically significant improvements in obese adolescents at risk of type 2 diabetes.Trial registrationAustralian New Zealand Clinical Trail Registry ACTRN12608000416392. Registered 25 August 2008.BMC Pediatrics 11/2014; 14(1):289. DOI:10.1186/s12887-014-0289-0 · 1.92 Impact Factor
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ABSTRACT: Objectives Recent cross-sectional data indicate the rates of childhood obesity are plateauing. Few large-scale longitudinal data sets exist, particularly in low-income and minority youth. The purpose of this study was to describe longitudinal changes in relative weight among a large sample of low-income, minority youth over 1 year.Methods Participants were students from 56 schools in urban, low-income environments. There were 17,727 first- to sixth-graders (64% African–American, 52% male) assessed at baseline, and 13,305 youth (75.1%) were reassessed 1 year later at follow-up. Measured height and weight were used to assess categorical (overweight, obesity, severe obesity) and continuous (BMI, percentile, z-score) measures of relative weight.ResultsLongitudinal data showed that over 1 year, BMI percentile (95% CI.64-–0.32, P < 0.001) and BMI z-score (95% CI: –0.02-–0.01, P < 0.001) were significantly lower compared to baseline. The prevalence of overweight and obesity was stable over 1 year. Most (86.0%) youth remained in the same weight category as baseline, 6.8% improved weight category, and 7.2% worsened weight category over 1 year.Conclusions These longitudinal data indicate that the relative weight of low-income, urban youth is showing signs of a small improvement over a 1-year follow-up period. The rates of childhood obesity, however, remain remarkably high and require continued, creative public health efforts.Obesity 10/2014; DOI:10.1002/oby.20928 · 4.39 Impact Factor