Willem-Jan M. Gerver

Physical activity levels in children and adolescents

BACKGROUND: Reference data for physical activity level (PAL) and activity-related energy expenditure (AEE) are needed for a better understanding of the effect of activity on childhood health, growth and developmentOBJECTIVE: Data from 17 studies measuring TDEE (TDEE) with doubly labelled water DLW were combined to construct a reference line for PAL and AEE as a function of age.DESIGN: A total of 17 studies from the literature were analyzed; 17 on girls and 16 on boys. Children were aged 3–16 y and of Caucasian origin. Weighted least-squares regression was used to obtain reference lines for PAL and AEE as a function of age and gender. The relative numbers of children per study were used as a weighting factor. Basal metabolic rate (BMR) or nonfasted (NF) resting metabolic rate and sex were included in the analysis.RESULTS: Although there was no difference in PAL between boys and girls, a significant difference in AEE was found between the two sexes. PAL: 0.025 × age+1.40. AEE (MJ/day): boys 0.30 × age+0.025; girls 0.21 × age+0.33. If BMR is measured under NF conditions, the obtained value has to be reduced by 0.21 for PAL and 0.75 MJ/day for AEE. No relation was found between AEE/kg and age.CONCLUSIONS: PAL and AEE were found to increase with age, showing the importance of age-dependent recommendations. Recommendations for AEE need to be differentiated for sex. To compare PAL and AEE between studies, the measurement conditions of BMR have to be taken into account. The increase in PAL and AEE values can be attributed to an increase in weight, because there was no relation between AEE/kg and age.

Activity related energy expenditure in children and adolescents with Prader-Willi syndrome

OBJECTIVE: To measure activity related energy expenditure in Prader–Willi syndrome (PWS) corrected for body size.SUBJECTS: 17 PWS subjects (10 females, seven males, age 7.5–19.8 y) and 17 obese controls, matched for gender and bone age.MEAUREMENTS: Basal metabolic rate (BMR) was measured by ventilated hood and average daily metabolic rate (ADMR) was measured with doubly labelled water. Activity induced energy expenditure (AEE) was calculated as 0.9ADMR −BMR. Activity related energy expenditure was corrected for body size using the following measures: AEE per kg body weight (AEE/kg), ADMR/BMR (PAL), and the residual of the regression of ADMR on BMR (rADMR). Group differences were analyzed by analysis of covariance adjusting for bone age, fat mass (FM) and gender.RESULTS: ADMR, AEE and PAL were lower (P<0.01) in the PWS group compared with the control group (7.14±1.72, 1.07±0.69 and 1.33±0.15 MJ/day compared with 9.94±2.64, 2.56±1.03 and 1.55±0.12 MJ/day respectively). The variance of AEE/kg and PAL was significantly explained by gender and PWS, while AEE was additionally explained by FM. The variance of rADMR was explained by PWS and not by FM or gender.CONCLUSION: Activity related energy expenditure is decreased in PWS compared with controls adjusted for bone age, FM and gender.

Body proportions during 6 years of GH treatment in children with short stature born small for gestational age participating in a randomised, double‐blind, dose–response trial*

The aim of this study was to assess body proportions in children with short stature born small for gestational age (SGA) before and during 6 years of growth hormone (GH) treatment.

Body composition in children based on anthropometric data - A presentation of normal values

Knowledge of the body composition in terms of fat and fatfree mass is used in paediatrics to estimate a childs nutritional status. To obtain the fat content or protein content sophisticated techniques exist. These techniques are often difficult to apply in daily practice. An anthropometric approach is therefore relevant because of its simplicity. In this study skinfold thicknesses and midupperarm circumference are presented as reference values and used to derive the fat-free mass fraction of the body and the arm muscle area.

Endothelial vasodilatation in newborns is related to body size and maternal hypertension.

Objective The fetal response to an adverse intrauterine environment – reflected in low birth weight – is thought to cause an increased risk for adult hypertension. A possible mechanism by which fetal adaptive responses contribute to hypertension is an adverse effect on endothelial function. Identifying individuals with endothelial dysfunction as early as possible may assist in understanding the inverse association between birth weight and hypertension. The present study aimed to identify determinants of endothelial vasodilatation in the first week of life. Methods One hundred and four term newborns were studied in the first week after birth with regard to maximum vasodilatation in response to acetylcholine (endothelium-dependent) and nitroprusside (endothelium-independent) in the vasculature of the forearm skin, by use of a laser-Doppler device and iontophoresis. Bivariable and multivariable linear regression with various familial, gestational and neonatal potential covariates were used for the analysis. Results In the bivariable analysis, maximum perfusion after administration of acetylcholine was positively associated with birth weight, length, head circumference and maternal education level, but negatively associated with maternal hypertension during pregnancy. In the multivariable analysis, head circumference [b = 11.9 perfusion units/z-score, P = 0.02] and hypertension during pregnancy (b = −25.3 perfusion units from nonhypertensive to hypertensive, P = 0.02) remained significantly associated. Maximum perfusion after administration of nitroprusside was not related to any of the anthropometric measures; it was, however, related to gestational age (b = −11.1 perfusion units/week, P = 0.009). Conclusion This study showed that body size, head circumference in particular, is positively associated with endothelial vasodilatation in newborns, whereas hypertension during pregnancy is inversely associated with endothelial vasodilatation.

Determinants of infant growth in four age windows: a twin study

OBJECTIVE To identify determinants of growth during infancy. STUDY DESIGN The sample included 424 twin pairs from the East Flanders Prospective Twin Survey. Multilevel regression analysis was performed and intrapair growth correlations were calculated. The main outcome measure was growth, measured in g/kg/d (0-1 month) or in change in weight z-score (0-6, 6-12 and 12-24 months). RESULTS Growth during infancy was associated with birth weight and gestational age. One z-score increase in birth weight resulted in -1.77 g/kg/d less growth from 0-1 month (P < .0001). The effect size decreased with age until -0.02 (P = .70) z-scores less growth from 12 to 24 months. Corresponding numbers for one z-score increase in gestational age decreased from 0.78 (P = .001) to 0.06 (P = .40). From 12 to 24 months, paternal height had a significant positive effect. The difference in growth similarity within the twin pair between monozygotic and dizygotic twins increased from non-significant from 0 to 1 month (P = .49) to a monozygotic:dizygotic ratio approximating 2:1 from 12 to 24 months (P = .002). CONCLUSION From 0 to 1 month, environmental factors are most important for growth, whereas genetic factors become more important over time. This is a first step in identifying age windows for future counseling and interventions on the effects of accelerated growth.

Influence of Growth During Infancy on Endothelium-Dependent Vasodilatation at the Age of 6 Months

Low birth weight and accelerated infant growth are associated with cardiovascular disease in adulthood. Endothelial dysfunction is regarded as a precursor of atherosclerosis and is also related to infant growth. We aimed to examine whether an association between infant growth and endothelial function is already present during discrete periods of growth during the first 6 months of life in healthy term infants. A cohort of 104 newborns was studied in the first week after birth and reexamined at the age of 6 months. Maximum vasodilatation in response to acetylcholine (endothelium dependent) and nitroprusside (endothelium independent) was measured in the vasculature of the forearm skin, using laser Doppler flowmetry and iontophoresis. Growth was calculated as difference in Z scores for weight, length, weight-for-length, and head circumference. Multivariable multilevel linear regression was used for the analysis. Growth from 0 to 1 month (calculated as difference in weight) was the only window in the first 6 months of life that was significantly and inversely associated with endothelium-dependent vasodilatation at 6 months (b=−11.72 perfusion units per Z score, P=0.01 in multivariable analysis). Birth size was not important when considered simultaneously with infant growth. Maximum endothelium-independent vasodilatation was not associated with birth size or growth parameters. We conclude that growth in the first month of life is inversely associated with endothelium-dependent vasodilatation at the age of 6 months in healthy term infants, regardless of birth size.

Effects of Discontinuation of Growth Hormone Treatment on Body Composition and Metabolism

This study was directed to the investigation of two different aspects of growth hormone: What are the metabolic consequences following the discontinuation of treatment and are these metabolic effects correlated with the growth-promoting effects seen in the first year of treatment? The study was performed on 12 growth hormone-deficient (GHD) patients who reached their final height. Each patient was matched with a non-GHD person of the same sex and about the same age. Immediately after the discontinuation of treatment, and 6 weeks and 6 months later, the following anthropometric variables were assessed: height, weight, skinfold thicknesses (biceps, triceps, subscapular and suprailiacal), body volume (underwater weighing) and total body water (deuterium dilution). To describe energy metabolism, basal metabolic rate assessed by ventilated hood, and sleep metabolic rate assessed by respiration chamber, were studied. Body composition was calculated from weight, volume and total body water. Clear metabolic effects were found after the discontinuation of treatment in GHD children: there was a decrease in fat free mass and sleep metabolic rate. Also, a strong correlation between the above-mentioned effects and the growth-promoting effects of human growth hormone at the beginning of the treatment was observed. The fact that this correlation exists poses the interesting question of whether the results from a test treatment lasting some weeks could be used to predict the long-term effects of hGH.

Longitudinal Growth during the First Years of Life: What Is Normal?

The anthropometric data of a longitudinal growth study on healthy infants, followed from birth until the age of 4 years and performed during 1995–1999 in The Netherlands, were used to analyze the general growth patterns in terms of height, weight and head circumference, based on z-scores, during the first 4 years of life. The well-known phenomenon where each infant or child tends to decelerate or accelerate its growth velocity depending on its starting position on the reference curve is obvious in this study too. This phenomenon, known as the regression to the mean, is a strong phenomenon especially during the first year. Regression to the mean is calculated for the different age groups as factor. With the given α, it is possible to estimate the individual expectation of growth.

Association of TSH With Cardiovascular Disease Risk in Overweight and Obese Children During Lifestyle Intervention

Context Overweight and obese children have an increased risk to develop cardiovascular diseases (CVDs) in which thyroid-stimulating hormone (TSH) has been suggested as an intermediary factor. However, results of cross-sectional studies are inconclusive, and intervention studies investigating changes in TSH concentrations in association with changes in cardiovascular risk parameters in overweight and obese children are scarce. Objective To gain insight in associations of circulating TSH concentrations and cardiovascular risk parameters in overweight and obese children. Design Nonrandomized lifestyle intervention. Setting Centre for Overweight Adolescent and Childrens Healthcare. Patients Three hundred thirty euthyroid overweight and obese children. Intervention Long-term lifestyle intervention. Main Outcome Measures TSH concentrations, pituitary TSH release in response to thyrotropin-releasing hormone (TRH), and cardiovascular risk parameters. Results At baseline, serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triacylglycerol (TAG), and monocyte chemotactic protein 1 concentrations were significantly associated with serum TSH concentrations. TSH release by the pituitary in response to exogenous TRH was not associated with cardiovascular risk parameters. During lifestyle intervention, several cardiovascular risk parameters significantly improved. In children whose body mass index z score improved, changes in TSH concentrations were significantly associated with changes in TC, LDL-C, and TAG concentrations. Conclusions In euthyroid overweight and obese children, circulating TSH concentrations are positively associated with markers representing increased CVD risk. Changes in TSH concentrations are also associated with changes in lipid concentrations in children with successful weight loss, which is consistent with TSH being an intermediary factor in modulating lipid and lipoprotein metabolism.