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Estimation of Hydration and Density of Fat-Free Mass in Indian Children Using a 4-Compartment Model: Implications for
Sulagna Bandyopadhyay1, Deepa Puttaswamy1, Mamatha Philip Gabriel1
1Division of Nutrition, St. John's Research Institute, St. John's National Academy of Health Sciences, Bengaluru, Karnataka, India.
Insights
Accurate body fat mass measurement in South Asian children is crucial. This study found that using ethnic-specific constants for fat-free mass hydration and density in 4-compartment models improves accuracy over standard 2-compartment models.
Area of Science:
- Human Physiology
- Nutritional Science
- Pediatrics
Background:
- Accurate body fat mass (FM) measurement is essential, especially for South Asian children who may exhibit higher adiposity for their size.
- Existing 2-compartment (2C) models for FM estimation rely on assumptions for fat-free mass (FFM) hydration and density, which may not be valid for this population.
Purpose of the Study:
- To determine FFM hydration and density in South Indian children using a 4-compartment (4C) model.
- To compare FM estimates derived from the 4C model with those from 2C models utilizing literature-reported constants.
Main Methods:
- A 4C model was employed, measuring total body water (TBW), bone mineral content (BMC), and body volume in 299 South Indian children (ages 6-16).
- Deuterium dilution, DXA, and air displacement plethysmography were used to obtain TBW, BMC, and body volume, respectively.
- FM was calculated using both 4C and 2C models, and agreement between the methods was assessed.
Main Results:
- FFM hydration and density values in South Indian children differed significantly from published general values.
- Using study-specific constants reduced hydrometry-based FM estimates by 3.5% and increased densitometry-based 2C estimates by 5.2%.
- Discrepancies between 2C and 4C FM estimates were -1.1 ± 0.9 kg for hydrometry and 1.6 ± 1.1 kg for densitometry.
Conclusions:
- Standard FFM hydration and density constants can lead to significant errors (±12% to ±17%) in FM calculations for Indian children when using 2C models.
- Employing a 4C model with ethnic-specific constants is recommended for more accurate body composition assessment in this population.
Background:
Accurate methods are needed to measure body fat mass (FM), particularly in South Asian children who are thought to have greater adiposity for a given body size. The accuracy of simple 2-compartment (2C) models of measuring FM depends on the primary measurement of the fat free mass (FFM) and the validity of assumed constants for FFM hydration and density. These have not been measured in this particular ethnic group.
Objectives:
To measure FFM hydration and density in South Indian children using a 4-compartment (4C) model and to compare FM estimates from this 4C-model with 2C-model-based estimates from hydrometry and densitometry, using literature-reported FFM hydration and density in children.
Methods:
This study included 299 children (45% boys), aged 6-16 y from Bengaluru, India. Total body water (TBW), bone mineral content (BMC), and body volume were measured using deuterium dilution, dual-energy X-ray absorptiometry, and air displacement plethysmography, respectively, to calculate the FFM hydration and density, and the FM using 4C and 2C models. The agreement between FM estimates from 2C and 4C models was also evaluated.
Results:
Mean FFM hydration and density were 74.2% ± 2.1% and 71.4% ± 2.0% and 1.095 ± 0.008 kg/L and 1.105 ± 0.008 kg/L in boys and girls respectively, which were significantly different from published values. Using the presently estimated constants, the mean hydrometry-based FM (as % body weight) estimates decreased by 3.5% but increased by 5.2% for densitometry-based 2C methods. When 2C-FM (using previously reported FFM hydration and density) were compared with 4C-FM estimates, the mean difference was -1.1 ± 0.9 kg for hydrometry and 1.6 ± 1.1 kg for densitometry.
Conclusions:
Previously published constants of hydration and density of FFM may induce errors of -12% to +17% in FM (kg) when using different 2C models in comparison to the 4C models in Indian children. J Nutr 20xx;x:xx.
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