Body composition measured by dual-energy X-ray absorptiometry half-body scans in obese children

Aim: To perform a methods comparison of a left or right half‐body scan versus whole‐body scan for measuring body composition in a sample of obese children. Methods: A group of obese children (n = 58; ≥95th BMI percentile; 8–18 years) were required to undergo a dual‐energy X‐ray absorptiometry (DXA) body composition measurement as part of an ongoing cohort study; 34 fit within the imaging field of the DXA scanner and were eligible for inclusion in the present analysis. Percent fat, total mass, fat mass, lean mass and bone mineral content (BMC) were estimated from half‐body scans and compared with the whole‐body results. Assessment was completed using GE enCORE 11.40 software. Results: In comparing left‐ and right‐side scans to whole‐body scans, there was significant correlation for all body composition variables (p ≤ 0.005, R² = 0.996–1.0). Bland Altman analyses also showed high levels of agreement between half‐body estimates and whole‐body measurements. Conclusion: This study supports using a half‐body scan methodology for percent fat, total mass, fat mass, lean mass, and BMC as a valid alternative to full‐body analysis in obese children and youth.     

Human body composition as related to surface area

There is a linear relationship between extracellular fluid and body surface area in man. During growth the body cell mass, fat-free solids, and body fat proportions of body weight increase while the extracellular fluid fraction decreases. Growth stops in men as soon as the body cell mass reaches 22.5 kg/m² body surface area and in women when it reaches 16.9 kg/m². The non-muscle cell mass and the muscle cell mass reach a 1:4 ratio in men whereas in women a 1:3.5 proportion—which is more favorable for pregnancy and lactation—is reached. The body composition of the newborn and the infant have fetal characteristics with a low body fat: surface area ratio and a low non-muscle cell mass: surface area ratio. The basal metabolic rate depends on the amount of non-muscle cell mass present, and the total energy change depends on body cell mass.This has been established by measurements of total body potassium, thiosulfate space, total body sodium, 24 h urine creatinine values and basal metabolic rate.Abbreviations BCM body cell mass (kg) - BF depot fat (kg) - Cr creatinine in urine (g/day) - ECF extracellular fluid (kg) - EFFS extracellular fatfree solids (kg) - H height (cm) - ICF intracellular fluid (kg) - L length (cm) - LBM lean body mass (kg) - n number of cases investigated - MCM muscle cell mass (kg) - nMCM non-muscle cell mass (kg) - SA surface area (m²) - TBK total body potassium (mmol) - TBNa total body sodium (mmol) - TBW total body water (kg) - W body weight (kg) Dedicated to Prof. Dr. H. R. Wiedemann on occasion of his 65th birthday     

Daily physical activity related to body fat in children aged 8-11 years

OBJECTIVE: To evaluate the association between objectively measured daily physical activity and body fat. STUDY DESIGN: Cross-sectional, observational, study of 248 children aged 7.9 to 11.1 years. Abdominal fat mass and total body fat mass were measured by dual-energy X-ray absorptiometry. Daily physical activity was assessed by accelerometers for 4 days. RESULTS: Total body fat expressed as a percentage of body mass was inversely related to minutes of vigorous physical activity per day, for all children r = -0.38 (P < .05). Children, both boys and girls, in the highest quartile of body fat performed on average 12 minutes less vigorous activity per day compared with their counterparts in the lowest quartile. Multiple regression analysis revealed that independent factors for body fat were number of minutes of vigorous activity per day and sex. CONCLUSION: Low physical activity can be a contributing factor in childhood obesity. Only longitudinal studies, however, can give more definitive information about the relation between daily physical activity and obesity.     

北京地区儿童性别年龄别身体组成成分检测的意义

目的应用电阻抗法了解北京地区正常儿童性别年龄别身体组成成分。方法选择北京市西城区中、小学6~14岁、相对体质量在正常范围(80%~120%)内的健康儿童587名,排除慢性疾病。用电阻抗法测量和计算体脂肪(BF)率、体脂肪量、除脂肪量。结果除脂肪量和脂肪量在男、女童两组均随着年龄的增加而增加。男童组各年龄段除脂肪量高于女童组,体脂肪率低于女童组。当体质量指数(BMI)<20 kg/m2时,男、女童BF率显示一个高值状态。结论我国儿童体BF率比BMI预计的要高。     

Percent body fat,skinfold thickness or body mass index for defining obesity or overweight,as a risk factor for asthma in schoolchildren: which one to use in epidemiological studies?

None of the epidemiological studies indicating that obesity is a risk factor for asthma in schoolchildren have used the percent body fat (PBF) to define obesity. The present study compares the definition of obesity using body mass index (BMI), PBF and the raw sum of the thickness of four skinfolds (SFT) to evaluate this condition as a risk factor for asthma. All classes of children of the target ages of 6-8 years of all schools in four municipalities of Murcia (Spain) were surveyed. Participation rate was 70.2% and the number of children included in the study was 931. Height, weight and SFT (biceps, triceps, subscapular and suprailiac) were measured according to standard procedures. Current active asthma was defined from several questions of the International Study of Asthma and Allergies in Childhood questionnaire. Obesity was defined using two standard cut-off points for BMI and PBF, and the 85th percentile for BMI, PBF and SFT. The highest quartile of each type of measurement was also compared with the lowest. A multiple logistic regression analysis was made for the various obesity definitions, adjusting for age, asthma in the mother and father and gender. The adjusted odds ratios of having asthma among obese children were different for boys and girls and varied across the different obesity definitions. For the standard cut-off points of BMI they were 1.19 [95% confidence interval (CI) 0.41-3.43] for girls and 2.00 (95% CI 0.97-4.10) for boys; however, for PBF (boys 25%, girls 30%) the corresponding figures were 1.54 (95% CI 0.63-3.73) and 1.20 (95% CI 0.66-2.21). BMI, PBF and SFT showed more consistency between each other when using the other cut-off points. BMI, PBF (except standard cut-off points) and SFT produce relatively comparable results when analysing the interaction between obesity and asthma.     

Smoking and metabolic control in adolescents with type 1 diabetes

OBJECTIVE: To relate self-reported smoking frequency to metabolic control and other cardiovascular risk factors in adolescents with type 1 diabetes. STUDY DESIGN: In the multicenter Diabetes Patienten Verlaufsdokumentationssystem database from Germany and Austria, anonymized records on 27 561 patients < 20 years of age with documented smoking status were available for analysis. RESULTS: Self-reported smoking was negligible in patients younger than 11 years (0.1%), increasing to 5% in 11- to 15-year-old patients, and 28.4% in the 15- to 20-year-old age group. Multivariate analysis with adjustment for age, diabetes duration, sex, insulin therapy, and center differences, revealed that smokers had higher HbA1c-levels compared with non-smokers (9.1% vs 8.0%, P < .0001). Diastolic blood pressure was higher (68.2 vs 67.6 mm Hg, P < .0001), and the lipid profile was unfavorable in patients who smoke: Triglycerides and total cholesterol were higher and high-density lipoprotein-cholesterol was lower (all P < .0001). CONCLUSIONS: Smokers display significantly worse metabolic control and a higher cardiovascular risk profile. Although not attested in trials, we state that education about smoking, smoking prevention, and psychological help for smoking cessation should be an integral part of comprehensive pediatric care for adolescent patients with type 1 diabetes.     

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.     

Television viewing in early childhood predicts adult body mass index

OBJECTIVES: To examine the effects of duration, timing and type of television (TV) viewing at age 5 years on body mass index (BMI) in adult life. STUDY DESIGN AND METHODS: 1970 British Birth Cohort, followed up at 5 (N=13,135), 10 (N=14,875), and 30 years (N=11,261). OUTCOME MEASURES: Weekday and weekend TV viewing at 5 years, type of programs, and maternal attitudes toward TV at age 5 years. BMI z-score at 10 and 30 years. RESULTS: Mean daily hours of TV viewed at weekends predicted higher BMI z-score at 30 years (coefficient=0.03, 95% CI: 0.01, 0.05, P=.01) when adjusted for TV viewing and activity level at 10 years, sex, socioeconomic status, parental BMIs, and birth weight. Each additional hour of TV watched on weekends at 5 years increased risk of adult obesity (BMI > or =30 kg/m2) by 7% (OR=1.07, 95% CI 1.01, 1.13, P=.02). Weekday viewing, type of program and maternal attitudes to TV at 5 years were not independently associated with adult BMI z-score. CONCLUSIONS: Weekend TV viewing in early childhood continues to influence BMI in adulthood. Interventions to influence obesity by reducing sedentary behaviors must begin in early childhood. Interventions focusing on weekend TV viewing may be particularly effective.     

Use of skin-fold thickness in Sri Lankan children: Comparison of several prediction equations

Objective  There are many prediction equations available in the literature for the assessment of body composition from skinfold thickness (SFT). This study aims to cross validate some of those prediction equations to determine the suitability of their use on Sri Lankan children. Methods  Height, weight and SFT of 5 different sites were measured. Total body water was assessed using the isotope dilution method (D₂O). Percentage Fat mass (%FM) was estimated from SFT using prediction equations described by five authors in the literature. Results  Five to 15 year old healthy, 282 Sri Lankan children were studied. The equation of Brook gave Ihe lowest bias but limits of agreement were high. Equations described by Deurenberg et al gave slightly higher bias but limits of agreement were narrowest and bias was not influence by extremes of body fat. Although prediction equations did not estimate %FM adequately, the association between %FM and SFT measures, were quite satisfactory. Conclusion  We conclude that SFT can be used effectively in the assessment of body composition in children. However, for the assessment of body composition using SFT, either prediction equations should be derived to suit the local populations or existing equations should be cross-validated to determine the suitability before its application.     

Age- and sex-specific body composition of Chinese children

We examined age- and sex-specific body compositions of Chinese children by the bioelectrical impedance method. The subjects were a total of 587 children aged 6-14 y who had normal relative weight. In all ages, boys had larger fat-free mass and lower percent body fat (%BF) than girls did. Even in the subjects with BMI <20 kg/m2, more than one quarter of them had high %BF. CONCLUSION: Chinese children may have higher %BF than that predicted by BMI.