Longitudinal assessment of body composition in healthy Swedish children from 1 week until 4 years of age

Prediction of fat-free mass in young children using bioelectrical impedance spectroscopy

BACKGROUND

Bioimpedance devices are practical for measuring body composition in preschool children, but their application is limited by the lack of validated equations.

OBJECTIVES

To develop and validate fat-free mass (FFM) bioimpedance prediction equations among New Zealand 3.5-year olds, with dual-energy X-ray absorptiometry (DXA) as the reference method.

METHODS

Bioelectrical impedance spectroscopy (SFB7, ImpediMed) and DXA (iDXA, GE Lunar) measurements were conducted on 65 children. An equation incorporating weight, sex, ethnicity, and impedance was developed and validated. Performance was compared with published equations and mixture theory prediction.

RESULTS

The equation developed in ~70% (n = 45) of the population (FFM [kg] = 1.39 + 0.30 weight [kg] + 0.39 length2/resistance at 50 kHz [cm2/Ω] + 0.30 sex [M = 1/F = 0] + 0.28 ethnicity [1 = Asian/0 = non-Asian]) explained 88% of the variance in FFM and predicted FFM with a root mean squared error of 0.39 kg (3.4% of mean FFM). When internally validated (n = 20), bias was small (40 g, 0.3% of mean FFM), with limits of agreement (LOA) ±7.6% of mean FFM (95% LOA: -0.82, 0.90 kg). Published equations evaluated had similar LOA, but with marked bias (>12.5% of mean FFM) when validated in our cohort, likely due to DXA differences. Of mixture theory methods assessed, the SFB7 inbuilt equation with personalized body geometry values performed best. However, bias and LOA were larger than with the empirical equations (-0.43 kg [95% LOA: -1.65, 0.79], p < 0.001).

CONCLUSIONS

We developed and validated a bioimpedance equation that can accurately predict FFM. Further external validation of the equation is required.

Body composition reference charts for infants from birth to 24 months: Multicenter Infant Body Composition Reference Study

BACKGROUND

Body composition assessment in the first 2 y of life provides important insights into child nutrition and health. The application and interpretation of body composition data in infants and young children have been challenged by a lack of global reference data.

OBJECTIVES

We aimed to develop body composition reference charts of infants aged 0-6 mo based on air displacement plethysmography (ADP) and those aged 3-24 mo based on total body water (TBW) by deuterium dilution (DD).

METHODS

Body composition was assessed by ADP in infants aged 0-6 mo from Australia, India, and South Africa. TBW using DD was assessed for infants aged 3-24 mo from Brazil, Pakistan, South Africa, and Sri Lanka. Reference charts and centiles were constructed for body composition using the lambda-mu-sigma method.

RESULTS

Sex-specific reference charts were produced for FM index (FMI), FFM index (FFMI), and percent FM (%FM) for infants aged 0-6 mo (n = 470 infants; 1899 observations) and 3-24 mo (n = 1026 infants; 3690 observations). When compared with other available references, there were observable differences but similar patterns in the trajectories of FMI, FFMI, and %FM.

CONCLUSIONS

These reference charts will strengthen the interpretation and understanding of body composition in infants across the first 24 mo of life.

Body composition from birth to 2 years in term healthy Indian infants measured by deuterium dilution: Effect of being born small for gestational age and early catch-up growth

OBJECTIVES

South Asian body composition is characterized by higher body fat at any given BMI. While this does not occur during fetal growth, it is important to understand if inappropriate fat accretion then begins in the first 2 years in Indian infants.

METHODS

The fat mass (FM) and fat-free mass (FFM) of healthy term newborns was evaluated at 12 days, 3.5 months, 1 year, and 2 years, by deuterium oxide (D₂O) dilution. The effect of being born small versus appropriate for gestational age (SGA vs. AGA), and accelerated early growth pattern on FM and FFM accretion was also investigated.

RESULTS

Newborns (262 total, 150 males) with mean birth weight of 2863 ± 418 g were enrolled. FM percentage (FM%) assessed by D₂O in 144, 166, 81, and 115 infants at 12 days, 3.5 months, 1 year, and 2 years respectively, was11.6 ± 6.8, 21.1 ± 7.0, 17.9 ± 8.2 and 22.4 ± 9.5%. Boys had higher FFM at all ages, but FM% was similar in both sexes. Children born SGA had similar FM index (FMI) but a lower FFM index (FFMI) at 2 years compared with those born AGA. Infants with catch-up growth between 0 and 2 years had higher FMI at 2 years compared to those without. Infants in the present study had a lower FM% and FMI till 1 year of age in comparison to previous studies from other countries, but had an increase in adiposity between 1 and 2 years, whereas in previous studies FM% remained stable or declined between 1 and 2 years of age.

CONCLUSION

There was an upward inflection in the curve of FM% and FMI between 1 and 2 years of age in the present study, which may represent an early adiposity rebound. Further longitudinal body composition data for Indian infants as well as those of other ethnicities but with low birth weight will clarify whether early accelerated growth pattern contributes to greater accrual of fat rather than lean mass during childhood.

Methods to Assess Fat Mass in Infants and Young Children: A Comparative Study Using Skinfold Thickness and Air-Displacement Plethysmography

Background: Traditionally, fat mass is estimated using anthropometric models. Air-displacement plethysmography (ADP) is a relatively new technique for determining fat mass. There is limited information on the agreement between these methods in infants and young children. Therefore we aimed to longitudinally compare fat mass percentage values predicted from skinfold thicknesses (SFTs) and ADP in healthy infants and young children. Methods: Anthropometry and body composition were determined at the ages of 1, 4, and 6 months and 2 years. We quantified the agreement between the two methods using the Bland–Altman procedure, linear mixed-model analysis, and intra-class correlation coefficients (ICC). Results: During the first 6 months of life, fat mass% predicted with SFT was significantly different from that measured with ADP in healthy, term-born infants (n = 245). ICCs ranged from 0.33 (at 2 years of age) and 0.47 (at 4 months of age). Although the mean difference (bias) between the methods was low, the Bland–Altman plots showed proportional differences at all ages with wide limits of agreement. Conclusions: There is poor agreement between ADP and SFTs for estimating fat mass in infancy or early childhood. The amount of body fat was found to influence the agreement between the methods.

Bioelectrical Impedance Analysis-An Easy Tool for Quantifying Body Composition in Infancy?

There has been increasing interest in understanding body composition in early life and factors that may influence its evolution. While several technologies exist to measure body composition in infancy, the equipment is typically large, and thus not readily portable, is expensive, and requires a qualified operator. Bioelectrical impedance analysis shows promise as an inexpensive, portable, and easy to use tool. Despite the technique being widely used to assess body composition for over 35 years, it has been seldom used in infancy. This may be related to the evolving nature of the fat-free mass compartment during this period. Nonetheless, a number of factors have been identified that may influence bioelectrical impedance measurements, which, when controlled for, may result in more accurate measurements. Despite this, questions remain in infants regarding the optimal size and placement of electrodes, the standardization of normal hydration, and the influence of body position on the distribution of water throughout the body. The technology requires further evaluation before being considered as a suitable tool to assess body composition in infancy.

Measuring growth and medium- and longer-term outcomes in malnourished children

Severe and moderate acute malnutrition are among the leading causes of mortality among children in low- and middle-income countries. There is strong evidence that growth assessed anthropometrically from conception to 2 years of age marks later risk of ill health. This is central to the concept of the developmental origins of adult disease and is presumed to be related to modification of developmental processes during critical "window(s)" of vulnerability. Interventions to treat acute malnutrition have resulted in dramatic increase in the number of affected children surviving. Ensuring that these children thrive to fulfil their full physical and cognitive potential is a new challenge. Integral to this challenge is the need to be able to measure how earlier insults relate to the ability to survive and thrive to productive adulthood. Despite its obvious value, routine anthropometry does not adequately indicate how earlier adverse exposures affect more refined aspects of growth. Anthropometry is inadequate for predicting how disruption of healthy growth might modulate risk of disease or any subsequent interventions that correct this risk. A clear characterisation of healthy child growth is needed for determining which component best predicts later outcomes. The extent to which postnatal acute malnutrition is a consequence of maternal factors acting preconception or in utero and their relationship to postnatal health and long-term risk of non-communicable diseases is not clear. Body-composition measurement has significant untapped potential allowing us to translate and better understand the relationship between early insults and interventions on early growth in the short-term and long-term health outcomes.