Associations of body adiposity index, body mass index, waist circumference, and percentage of body fat in young female Emirati adults.

Body Adiposity Index (BAI), which relies on an individual's hip circumference and height, was proposed as an alternative anthropometric measurement to Body Mass Index (BMI). Although this measure has been validated across different populations, its accuracy in predicting percent body fat (%BF) in the United Arab Emirates has not yet been assessed. The objective of this study was to examine the association between BAI, BMI, Waist Circumference (WC), and %BF in young female Emirati adults and determine the relative accuracy of BAI when predicting %BF. A retrospective cross-sectional study was conducted among 95 Emirati women between the ages of 17 and 27. The %BF was measured using the dual-energy X-ray absorption (DXA) scanner. Anthropometric measurements were collected, and BMI and BAI were calculated. BMI and %BF (r = 0.823, p <0.001) showed a greater association than that between BAI and %BF (r = 0.702, p <0.001). A linear regression analysis revealed that BMI was the single best predictor of %BF in the sample (r2 = 0.678, p<0.001). The variation around the regression line for BAI comparisons with %BF (standard error of estimate = 4.879) was greater than BMI comparisons (standard error of estimate = 3.889). BAI was found to significantly underestimate %BF at higher adiposity levels (mean difference = 8.7%). The ROC curve analysis demonstrated that BMI had a higher discriminatory capacity (AUC = 0.891) over WC and BAI. The results demonstrated that BMI was a better predictor of %BF in the sample than BAI and WC. Thus, BMI may be more useful in assessing adiposity in young female Emirati adults than BAI. However, the potential of BAI as an alternative measure of adiposity should continue to be examined.

Validity of self-reported weight and height among female young adults in the United Arab Emirates.

Self-reported weight and height serve as important metrics in estimating overweight and obesity prevalence within epidemiological studies, primarily due to their cost and time efficiency. However, the accuracy and reliability of these self-reported measures remain controversial, with conflicting reports emerging from different regions. This study aims to compare self-reported weight and height with measured values among young female adults in the United Arab Emirates. A cross-sectional study of 131 female university students aged 17-27 reported their weight and height on a self-administered questionnaire and on the same day had their height and weight measured. Body Mass Index (BMI) values of both self-reported and measured weight and height were calculated and categorized according to the World Health Organization's cut-off points. Overall, 87% of students had a resultant self-reported BMI value within their actual BMI category. The mean differences between self-reported and measured weight and height in the present study were -0.92 kg and 0.38 cm, respectively. Results indicated strong agreement between self-reported and direct measurements, as demonstrated by weighted Kappa statistics (kappa = 0.87). Bland & Altman plots illustrated that the majority of values fell within the limits of agreement (2 SD), with no systemic bias detected. BMI calculated from self-reported data demonstrates high sensitivity and specificity. Linear regression analyses revealed that self-reported weight (r2 = 0.973; p<0.001), height (r2 = 0.902; p<0.001), and BMI (r2 = 0.964; p<0.001) accurately predicted measured weight, height, and BMI. The study's results highlight the ability of female university students in the UAE to accurately provide self-reports of their weight and height. This finding provides further support for the utilization of self-reported data on height and weight as a valid method for collecting anthropometric information.

Prevalence of Bullying Behaviors Among Students From a National University in the United Arab Emirates: A Cross-Sectional Study.

Background: This study aims to investigate bullying behaviors among college students at one of the national universities in UAE, and also to examine the psychological characteristics of those who were exposed to, or have experienced bullying. Methods: A cross-sectional study was conducted on 839 undergraduate students at one of the national universities in the UAE. Students from all colleges participated in this study and were selected by using stratified random sampling. Participants completed a bullying survey designed for the study, in addition to three psychological measures [i.e., Aggression Questionnaire, Buss and Perry, 1992; The Primary Care Anxiety and Depression, El-Rufaie et al., 1997; and the Post Traumatic Stress Disorder (PTSD) for Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (PCL-5), Weathers et al., 2013]. Results: The prevalence rate of students being exposed to or engaged in bullying was 26.3% (221 out of 839). Of those, 72 students (8.7%) reported being bullied, 29 (3.6%) reported bullying others, and 185 (22.8%) reported witnessing friends being bullied. The most common types of bullying reported were traditional bullying (e.g., face-to-face bullying, verbal, and physical). Cyberbullying was not very common. More females reported being bullied in comparison to males and most of the aggressors were peer students. Overall, moderate level of aggressive personality traits and low levels of symptoms of depression, anxiety, and PTSD were reported for the total sample. T-tests revealed significant differences in the three psychological measures between those who did not experience bullying and those who did. The mean scores on the Aggression Questionnaire for those who bullied others were significantly higher than those who did not experience bullying. Conclusion: Experiences of bullying seem to impact college students' mental health in the UAE. Therefore, efforts need to focus on developing preventive programs to increase students' awareness of bullying and its negative impact on campus environment. Offering psychological help for those who were exposed to bullying would help them to deal effectively with this trauma.

The Mineral Composition of Date Palm Fruits (Phoenix dactylifera L.) under Low to High Salinity Irrigation.

Adaptability to salinity varies between different varieties of date palm trees. This research aims to explore the long-term impact of different salinity irrigation levels on the mineral content of 13 date palm varieties grown in the United Arab Emirates (UAE). Date varieties were grown using three irrigation water salinity levels of 5, 10 and 15 dS m-1. The mineral composition (B, Ca, Cu, Fe, K, Mg, Na, P and Zn) of date palm fruits was determined using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). High salinity levels showed no effect on the mineral content of Ajwat AlMadinah, Naghal, Barhi, Shagri, Abu Maan, Jabri, Sukkari and Rothan varieties. All date varieties remained good sources of dietary potassium, magnesium, manganese and boron even at high salinity levels. Increased salinity had no effect on the percent Daily Value (%DV) categories of most of the analyzed minerals. While no genotypes showed a general adaptation to different saline environments, Barhi, Ajwat Al Madinah, Khinizi, Maktoumi and Shagri varieties were more stable towards salinity variation. In the UAE, the genotype x saline-environment interaction was found to be high which makes it impossible to attribute the variation in mineral content to a single varietal or salinity effect.

Urinary minerals excretion among primary schoolchildren in Dubai-United Arab Emirates.

INTRODUCTION: Urinary excretion of calcium (Ca), magnesium (Mg), phosphorus (P), iodine and fluoride is used to assess their statuses and/or the existence of metabolic abnormalities. In the United Arab Emirates (UAE), the urinary concentration of these minerals among children have not been documented. MATERIALS AND METHODS: A cross-sectional study, including 593 subjects (232 boys and 361 girls), was conducted among healthy 6 to 11-year-old Emirati children living in Dubai. Non-fasting morning urine samples and anthropometrical measurements were collected and analyzed. Results were expressed as per mg of creatinine (Cr). RESULTS: On average, estimated Cr excretion was 17.88±3.12 mg/kg/d. Mean urinary Ca/Cr, Mg/Cr and P/Cr excretions were 0.08±0.07 mg/mg, 0.09±0.04 mg/mg, and 0.57±0.26 mg/mg respectively. Urinary excretion of Ca, Mg and P were found to decrease as age increased. Urinary excretion and predicted intake of fluoride were lower than 0.05 mg/kg body weight per day. Surprisingly, more than 50% of the children were found to have urinary iodine excretion level above adequate. CONCLUSION: The Emirati schoolchildren had comparable levels of urinary Ca, Mg and P excretion to other countries. The 95% percentile allows the use of the current data as a reference value for the detection of mineral abnormalities. Fluoride excretion implies that Emirati children are at low risk of fluorosis. The level of urinary iodine excretion is slightly higher than recommended and requires close monitoring of the process of salt iodization to avoid the harmful impact of iodine overconsumption.

Maternal investment, life-history trajectory of the off-spring and cardiovascular disease risk in Emirati females in the United Arab Emirates.

BACKGROUND: Variations in cardiovascular disease risk (CVD) are suggested to be partly influenced by factors that affect prenatal growth patterns and outcomes, namely degree of maternal investment (proxied by birth weight and gestational age). Using the life history trajectory model, this study investigates whether maternal investment in early prenatal life associates with menarcheal age and whether maternal investment affects CVD risk in adulthood and predicts adult size and adiposity levels. METHODS: A cross-sectional study was conducted among 94 healthy Emirati females. Birth weight, gestational age and menarcheal age were obtained. Anthropometrical measurements, body composition analysis, and blood pressure values were collected. Regression analyses were conducted to establish associations. RESULTS: There was no association between birth weight standard deviation score (SDS) and age at menarche. When investigating the associations of birth weight SDS and age at menarche with growth indices, it was found that only birth weight was positively and significantly associated with both height (ß = 1.342 cm, 95% CI (0.12, 2.57), p = 0.032) and leg length (ß = 0.968 cm, 95% CI (0.08, 1.86), p = 0.034). Menarcheal age was significantly and inversely associated with fat mass index (FMI) (ß = - 0.080 cm, 95% CI (- 0.13, - 0.03), p = 0.002), but not with waist circumference and fat free mass index (FFMI) (p > 0.05). Birth weight SDS was positively and significantly associated with waist circumference (ß = 0.035 cm, 95% CI (0.01, 0.06), p = 0.009), FMI (ß = 0.087 cm, 95% CI (0.01, 0.16), p = 0.027), and FFMI (ß = 0.485 cm, 95% CI (0.17, 0.80), p = 0.003). Birth weight SDS was not significantly associated with either systolic blood pressure (SBP) or diastolic blood pressure (DBP) (p > 0.05). However, FMI, waist circumference, and FFMI were positively and significantly associated with SBP. Regarding DBP, the relationship was negatively and significantly associated with only FFMI (ß = - 1.6111 kg/m2, 95% CI (- 2.63, - 0.60), p = 0.002). CONCLUSION: Although the results do not fully support that Emirati females fast-life history is associated with increased chronic disease risk, the data does suggest a link between restricted fetal growth in response to low maternal investment and metabolic and reproductive health.

Development and validation of a prediction model for fat mass in children and adolescents: meta-analysis using individual participant data.

OBJECTIVES: To develop and validate a prediction model for fat mass in children aged 4-15 years using routinely available risk factors of height, weight, and demographic information without the need for more complex forms of assessment. DESIGN: Individual participant data meta-analysis. SETTING: Four population based cross sectional studies and a fifth study for external validation, United Kingdom. PARTICIPANTS: A pooled derivation dataset (four studies) of 2375 children and an external validation dataset of 176 children with complete data on anthropometric measurements and deuterium dilution assessments of fat mass. MAIN OUTCOME MEASURE: Multivariable linear regression analysis, using backwards selection for inclusion of predictor variables and allowing non-linear relations, was used to develop a prediction model for fat-free mass (and subsequently fat mass by subtracting resulting estimates from weight) based on the four studies. Internal validation and then internal-external cross validation were used to examine overfitting and generalisability of the model's predictive performance within the four development studies; external validation followed using the fifth dataset. RESULTS: Model derivation was based on a multi-ethnic population of 2375 children (47.8% boys, n=1136) aged 4-15 years. The final model containing predictor variables of height, weight, age, sex, and ethnicity had extremely high predictive ability (optimism adjusted R2: 94.8%, 95% confidence interval 94.4% to 95.2%) with excellent calibration of observed and predicted values. The internal validation showed minimal overfitting and good model generalisability, with excellent calibration and predictive performance. External validation in 176 children aged 11-12 years showed promising generalisability of the model (R2: 90.0%, 95% confidence interval 87.2% to 92.8%) with good calibration of observed and predicted fat mass (slope: 1.02, 95% confidence interval 0.97 to 1.07). The mean difference between observed and predicted fat mass was -1.29 kg (95% confidence interval -1.62 to -0.96 kg). CONCLUSION: The developed model accurately predicted levels of fat mass in children aged 4-15 years. The prediction model is based on simple anthropometric measures without the need for more complex forms of assessment and could improve the accuracy of assessments for body fatness in children (compared with those provided by body mass index) for effective surveillance, prevention, and management of clinical and public health obesity.

Metabolic syndrome among adolescents in Dubai, United Arab Emirates, is attributable to the high prevalence of low HDL levels: a cross-sectional study.

BACKGROUND: Metabolic syndrome (MetS) describes a combination of risk factors that increase the risk of developing chronic diseases. The prevalences of MetS and its risk factors are increasing, especially in the Arab region. A cross-sectional study was carried out to assess the prevalences of MetS and its associated risk factors among adolescents in the United Arab Emirates (UAE). METHODS: A total of 596 students (308 boys and 288 girls) aged 10 to 15.9 years old were recruited from 14 public secondary schools in Dubai, UAE. Anthropometric and biochemical data were measured. RESULTS: According to the International Diabetes Federation (IDF) criteria, the prevalence of MetS was 3.7%, and it was more common among boys than girls (12 boys versus 10 girls). MetS was also more likely to be found in students who were obese or overweight than those with normal weight. The most prevalent and significant MetS risk factor was low high-density lipoprotein (HDL) cholesterol levels. CONCLUSIONS: This study indicates the importance of carrying out further investigations about the constituents of HDL and their atherogenic effects. Additionally, these results strongly recommend setting a consensus for HDL measurement, since small variations in methodologies may lead to substantial deviations in results.

Assessing Knowledge of, and Attitudes to, HIV/AIDS among University Students in the United Arab Emirates.

BACKGROUND: The Middle East and North Africa (MENA) region is among the top two regions in the world with the fastest growing HIV epidemic. In this context, risks and vulnerability are high as the epidemic is on the rise with evidence indicating significantly increasing HIV prevalence, new HIV infections and AIDS-related deaths. OBJECTIVE: The aim of the survey was to assess HIV/AIDS knowledge and attitudes related to HIV/AIDS among a wide group of university students in the United Arab Emirates (UAE). METHODS: In a cross-sectional survey, a total sample of 2,294 students (406 male; 1,888 female) from four universities in three different Emirates in the UAE were approached to take part in the study. Students self-completed a questionnaire that was designed to measure their knowledge and attitudes to HIV/AIDS. RESULTS: The overall average knowledge score of HIV.AIDS was 61%. Non-Emirati and postgraduates demonstrated higher levels of knowledge compared to Emirati and undergraduate students respectively. No significant differences between males and females; and marital status were found. Eighty-five percent of students expressed negative attitudes towards people living with HIV, with Emirati and single students significantly holding more negative attitudes compared to non-Emiratis and those that are married respectively. CONCLUSIONS: The findings provide strong evidence that there is a need to advocate for appropriate National HIV/AIDS awareness raising campaigns in universities to reduce the gaps in knowledge and decrease stigmatizing attitudes towards people living with HIV/AIDS.

Body-composition reference data for simple and reference techniques and a 4-component model: a new UK reference child.

BACKGROUND: A routine pediatric clinical assessment of body composition is increasingly recommended but has long been hampered by the following 2 factors: a lack of appropriate techniques and a lack of reference data with which to interpret individual measurements. Several techniques have become available, but reference data are needed. OBJECTIVE: We aimed to provide body-composition reference data for use in clinical practice and research. DESIGN: Body composition was measured by using a gold standard 4-component model, along with various widely used reference and bedside methods, in a large, representative sample of British children aged from 4 to ≥20 y. Measurements were made of anthropometric variables (weight, height, 4 skinfold thicknesses, and waist girth), dual-energy X-ray absorptiometry, body density, bioelectrical impedance, and total body water, and 4-component fat and fat-free masses were calculated. Reference charts and SD scores (SDSs) were constructed for each outcome by using the lambda-mu-sigma method. The same outcomes were generated for the fat-free mass index and fat mass index. RESULTS: Body-composition growth charts and SDSs for 5-20 y were based on a final sample of 533 individuals. Correlations between SDSs by using different techniques were ≥0.68 for adiposity outcomes and ≥0.80 for fat-free mass outcomes. CONCLUSIONS: These comprehensive reference data for pediatric body composition can be used across a variety of techniques. Together with advances in measurement technologies, the data should greatly enhance the ability of clinicians to assess and monitor body composition in routine clinical practice and should facilitate the use of body-composition measurements in research studies.

Nutrient-based standards for school lunches complement food-based standards and improve pupils' nutrient intake profile.

Following concerns about the nutritional content of school lunches and the increased prevalence of overweight and obesity in the UK, changes to the standards of school meals were made. From September 2008, all primary schools in England were required, by law, to be fully compliant with the new food-based standards (FBS) and nutrient-based standards (NBS) for school lunches. The aim of the present survey was to evaluate the introduction of the NBS for school lunches on the nutritional profile of food and drink items provided by schools and chosen by pupils at lunchtime. A nationally representative sample of 6696 pupils from 136 primary schools in England aged 3-12 years and having school lunches was recruited. Data were collected on lunchtime food and drink provision at each school and on pupil food and drink choices at lunchtime. Caterers also provided planned menus, recipes and other cooking information. Compliance with both the FBS and NBS was then assessed. Results show that even when the FBS was met, many schools did not provide a school lunch that met the NBS as well. The average school lunch eaten was significantly lower in fat, saturated fat and Na in schools that met both the FBS and NBS for school lunches compared with schools that met only the FBS. Change in school lunch policy has contributed to improvements in pupils' choices and the nutritional profile of foods selected at lunchtime.

Short communicationKey differences between school lunches and packed lunches in primary schools in England in 2009.

OBJECTIVE: To compare the key differences between school lunches and packed lunches as consumed in a nationally representative sample of primary schools, 6-8 months after the nutrient-based standards for school lunch became mandatory. DESIGN: Data on 6580 pupils' school lunches and 3422 pupils' packed lunches were collected between February and April 2009 from pupils attending primary schools in England. Fieldwork was conducted over five consecutive school days. Fieldworkers randomly selected ten pupils taking a school lunch and five pupils bringing a packed lunch each day at each school, and recorded and weighed all food and drink items consumed, as well as any leftovers. SETTING: A nationally representative sample of 136 state-maintained primary schools in England. SUBJECTS: A total of 10 002 pupils aged 4-12 years. RESULTS: Mean intakes of protein, fat, saturated fat and vitamin C from both types of lunch met the nutrient-based standards. Pupils taking school lunches on average consumed significantly more protein, NSP, vitamin A, folate and Zn and less fat, saturated fat, non-milk extrinsic sugars (NMES), Na, Ca, vitamin C and Fe than pupils taking packed lunches. Energy intakes were low in both groups. CONCLUSIONS: Packed lunches were less likely to accord with food-based or nutrient-based standards than school lunches. Higher levels of Na, NMES, fat and percentage energy from saturated fat emphasise the difficulties associated with optimising nutrient intakes from packed lunches.

The impact of the food-based and nutrient-based standards on lunchtime food and drink provision and consumption in primary schools in England.

OBJECTIVE: To assess lunchtime provision of food and drink in English primary schools and to assess both choices and consumption of food and drink by pupils having school lunches. These findings were compared with similar data collected in 2005. DESIGN: Cross-sectional data collected between February and April 2009. In each school, food and drink provision, including portion weights and number of portions of each item served at lunchtime, were recorded over five consecutive days. Caterers provided school lunchtime menus and recipes. SETTING: England. SUBJECTS: A random selection of 6696 pupils having school lunches in a nationally representative sample of 136 primary schools in England. RESULTS: Compared with 2005, schools in 2009 provided significantly more fruit, fruit-based desserts, vegetables and salad, water and fruit juice, and less ketchup, sauces and gravy, starchy foods cooked in fat, snacks and confectionery (P < 0·01). Pupils were also making healthier choices, choosing an average of 2·2 portions of fruit and vegetables from their 'five a day', but about one-third to two-fifths of these were wasted. CONCLUSIONS: Lunchtime food provision and consumption in primary schools have improved substantially since 2005, following the introduction of new standards for school food in 2008. However, improvements still need to be made to increase the Fe and Zn content and to decrease the Na content of recipes, and in encouraging pupils to eat more of the fruits and vegetables taken at lunchtime.

Pediatric reference data for lean tissue properties: density and hydration from age 5 to 20 y.

BACKGROUND: Hydrometry and densitometry are widely used to assess pediatric body composition due to their ease of application. The accuracy of these techniques depends on the validity of age- and sex-specific constant values for lean tissue hydration or density. Empirical data on these constants, and their variability between individuals, are lacking. OBJECTIVES: The objectives were to measure lean tissue hydration and density in a large sample of children and adolescents and to derive prediction equations. DESIGN: Body composition was measured in 533 healthy individuals (91% white) aged 4-23 y by using the 4-component model. Age- and sex-specific median values for hydration and density were obtained by using the LMS (lambda, mu, sigma) method. Regression analysis was used to generate prediction equations on the basis of age, sex, and body mass index SD score (BMI SDS). Values were compared with those in previously published predictions. RESULTS: Age-associated changes in density and hydration differed between the sexes. Compared with our empirical values, use of published values resulted in a mean bias of 2.1% fat (P < 0.0001). Age, sex, and BMI SDS were all significant predictors of lean tissue hydration and density. With adjustment for age and sex, hydration was higher, and density lower, in higher-BMI SDS individuals. CONCLUSIONS: The chemical maturation of lean tissue is not a linear process and proceeds differently in males and females. Previously published reference values are inaccurate and induce clinically significant bias in percentage fat. New empirical reference values are provided for use in pediatric hydrometry and densitometry. Further research that extends to cover nonwhite ethnic groups is needed.

Validation of bioelectrical impedance analysis in adolescents across different ethnic groups.

Adolescent obesity is difficult to assess in multi-ethnic populations using BMI, due to variability in the BMI-fatness relationship. We aimed to describe body composition (BC), and to validate leg-leg bioelectrical impedance analysis (BIA), in adolescents from different ethnic groups using deuterium (D(2)O) as the reference method. Measurements were made of weight, height, total body water (TBW), and BIA (TANITA TBF-300) in 110 white, 170 Asian, and 102 black adolescents aged 11-15 years. TBW was converted to lean mass (LM) using assumed hydration of lean tissue. General linear models were used to compare BC by D(2)O between the ethnic groups. BC values from D(2)O were compared with TANITA values, and used to generate ethnic-specific prediction equations in the whole sample, and also in equation-generation (group 1) and cross-validation (group 2) subsamples. Ethnic variability in BMI did not reflect variability in adiposity. Asians had less LM than white and black adolescents, and less fat mass (FM) than white girls. TANITA in-built equations did not predict BC accurately across ethnic groups, with significant bias in white and Asian males, and Asian and black females. The new equation generated from the entire sample removes ethnic-specific mean biases. The group 1 equation showed no significant bias in any ethnic group when tested in group 2. We found significant variability in BC between ethnic groups that was not reflected by BMI. Manufacturers' equations are unsuitable for predicting BC in multi-ethnic populations, and our new equations are recommended.

Validation of BIA in obese children and adolescents and re-evaluation in a longitudinal study.

Decrease in fat mass (FM) is a one of the aims of pediatric obesity treatment; however, measurement techniques suitable for routine clinical assessment are lacking. The objective of this study was to validate whole-body bioelectrical impedance analysis (BIA; TANITA BC-418MA) against the three-component (3C) model of body composition in obese children and adolescents, and to test the accuracy of our new equations in an independent sample studied longitudinally. A total of 77 white obese subjects (30 males) aged 5-22 years, BMI-standard deviation score (SDS) 1.6-3.9, had measurements of weight, height (HT), body volume, total body water (TBW), and impedance (Z). FM and fat-free mass (FFM) were calculated using the 3C model or predicted from TANITA. FFM was predicted from HT(2)/Z. This equation was then evaluated in 17 other obese children (5 males) aged 9-13 years. Compared to the 3C model, TANITA manufacturer's equations overestimated FFM by 2.7 kg (P < 0.001). We derived a new equation: FFM = -2.211 + 1.115 (HT(2)/Z), with r(2) of 0.96, standard error of the estimate 2.3 kg. Use of this equation in the independent sample showed no significant bias in FM or FFM (mean bias 0.5 +/- 2.4 kg; P = 0.4), and no significant bias in change in FM or FFM (mean bias 0.2 +/- 1.8 kg; P = 0.7), accounting for 58% (P < 0.001) and 55% (P = 0.001) of the change in FM and FFM, respectively. Our derived BIA equation, shown to be reliable for longitudinal assessment in white obese children, will aid routine clinical monitoring of body composition in this population.

Aggregate predictions improve accuracy when calculating metabolic variables used to guide treatment.

BACKGROUND: Many components of clinical management are tailored to metabolic variables, such as fat-free mass, fat mass, resting metabolic rate (RMR), and body surface area. However, these traits are difficult to measure in routine care and are typically predicted from simple anthropometric or bedside body-composition measurements. Many prediction equations have been published, but validation studies have shown that these equations tend to have limited accuracy in individuals and many have significant average bias. OBJECTIVE: We tested a mathematical approach that assumes that the aggregate of many independent predictions is more accurate than the best single prediction. DESIGN: Body composition was measured in 196 children aged 4-16 y by using the 4-component model. RMR was measured in 142 adult women. Data on weight, height, age, skinfold thickness, and body impedance were used in published equations to predict body composition (12 equations) or RMR (13 equations). The accuracy of individual compared with aggregate predictions, relative to the reference measurements, was compared by using the Bland and Altman method. RESULTS: For children's body composition and adult RMR, the aggregate predictions had lower mean biases and lower limits of agreement than did the individual predictions, and the aggregate predictions performed better than did any individual prediction. CONCLUSIONS: Aggregate predictions perform better than single predictions at predicting fat-free mass, fat mass, total body water, and RMR. Our findings indicate that the accuracy of calculating variables such as energy requirements and drug and dialysis dosages can be improved significantly with the use of our mathematical approach.

Assessment of obesity status in outpatients from three disease states.

AIM: To assess obesity status in patients with cystic fibrosis (CF), human immunodeficiency virus (HIV) and various metabolic disorders (MD), through comparison against a) UK reference data and b) contemporary healthy children. METHODS: Weight, height, waist circumference (WC), and triceps (TRI) and sub-scapular (SUBS) skinfold thickness were measured in a total of 57 healthy, 49 HIV, 68 MD and 49 CF children. Using published reference data, standard deviation scores (SDS) were calculated. RESULTS: CF patients had weight, height and BMI SDS significantly below zero. MD patients had height SDS significantly below, and BMI SDS significantly above, zero. Healthy children had BMI SDS significantly above zero. In all three patient groups and healthy children, TRI and WC SDS were significantly above zero. SUBS SDS was also significantly above zero in patients with MD and HIV. WC SDS was greater in patients than in healthy children, but only significantly so for the MD children. CONCLUSION: In all three patient groups, even those associated with reduced stature or reduced weight, indices of fatness were significantly increased relative to reference data. The tendency to central fatness was evident in healthy children, but was more extreme in patients, especially those with MD.

Evaluation of Lunar Prodigy dual-energy X-ray absorptiometry for assessing body composition in healthy persons and patients by comparison with the criterion 4-component model.

BACKGROUND: Dual-energy X-ray absorptiometry (DXA) is widely used to assess body composition in research and clinical practice. Several studies have evaluated its accuracy in healthy persons; however, little attention has been directed to the same issue in patients. OBJECTIVE: The objective was to compare the accuracy of the Lunar Prodigy DXA for body-composition analysis with that of the reference 4-component (4C) model in healthy subjects and in patients with 1 of 3 disease states. DESIGN: A total of 215 subjects aged 5.0-21.3 y (n = 122 healthy nonobese subjects, n = 55 obese patients, n = 26 cystic fibrosis patients, and n = 12 patients with glycogen storage disease). Fat mass (FM), fat-free mass (FFM), and weight were measured by DXA and the 4C model. RESULTS: The accuracy of DXA-measured body-composition outcomes differed significantly between groups. Factors independently predicting bias in weight, FM, FFM, and percentage body fat in multivariate models included age, sex, size, and disease state. Biases in FFM were not mirrored by equivalent opposite biases in FM because of confounding biases in weight. CONCLUSIONS: The bias of DXA varies according to the sex, size, fatness, and disease state of the subjects, which indicates that DXA is unreliable for patient case-control studies and for longitudinal studies of persons who undergo significant changes in nutritional status between measurements. A single correction factor cannot adjust for inconsistent biases.