Prediction Equation for Physical Activity Energy Expenditure in 11-13-Year-Old Sri Lankan Children

This study aimed to develop a regression equation to predict physical activity energy expenditure (PAEE) using accelerometry. Children aged 11-13 years were recruited and randomly assigned to validation (n = 54) and cross-validation (n = 25) groups. The doubly labelled water (DLW) technique was used to assess energy expenditure and accelerometers were worn by participants across the same period. A preliminary equation was developed using stepwise multiple regression analysis with sex, height, weight, body mass index, fat-free mass, fat mass and counts per minute (CPM) as independent variables. Goodness-of-fit statistics were used to select the best prediction variables. The PRESS (predicted residual error sum of squares) statistical method was used to validate the final prediction equation. The preliminary equation was cross-validated on an independent group and no significant (p > 0.05) difference was observed in the PAEE estimated from the two methods. Independent variables of the final prediction equation (PAEE = [0.001CPM] - 0.112) accounted for 70.6% of the variance. The new equation developed to predict PAEE from accelerometry was found to be valid for use in Sri Lankan children.

A field tool for prediction of body fat in Sri Lankan women: skinfold thickness equation

BACKGROUND

Valid skinfold thickness (SFT) equations for the prediction of body fat are currently unavailable for South Asian women and would be a potentially robust field tool. Our aim was to assess the validity of existing SFT equations against deuterium (²H₂O) dilution and, if invalid, to develop and validate an SFT equation for % fat mass (%FM) in Sri Lankan women.

METHODS

H₂O dilution was used with Fourier transform infrared (FTIR) spectroscopy as the criterion method for the assessment of %FM in urban Sri Lankan women (30-45 years). This data was used to assess the validity of available SFT equations and to generate and validate a new SFT equation for the prediction of %FM against the criterion method. Women (n = 164) were divided into validation and cross-validation groups for the development and validation of the new equation. The level of agreement between the %FM calculated by the final derived prediction equation and the %FM obtained by ²H₂O dilution was assessed using Pearson's correlation coefficient (R) and Bland Altman plots. Student's t test was used to assess over- or underestimation, and significance was set at p < 0.05.

RESULTS

Existing equations significantly (p < 0.001) underestimated %FM compared with the ²H₂O dilution method. The final equation obtained was %FM = 19.621 + (0.237*weight) + (0.259*triceps). When compared with ²H₂O dilution, %FM by the equation was not significantly different. There was a significant (p < 0.001) correlation between %FM by the reference method and %FM by the equation. The limit of agreement by Bland Altman plot was narrow with a small mean positive bias.

CONCLUSIONS

Existing SFT equations were not applicable to this population. The new equation derived was valid. We report a new SFT equation to predict %FM in women of South Asian ancestry suitable for field use.

Body composition in urban South Asian women; development of a bioelectrical impedance analysis prediction equation

BACKGROUND

Assessment of body composition plays a significant role in combating chronic disease among South Asians. Accurate assessment of body composition by bioelectrical impedance analysis (BIA) requires population-specific equations which are currently unavailable for urban South Asian women.

AIM

To assess validity of direct BIA assessment and selected equations for prediction of total body water (TBW), against Deuterium ((2)H2O) dilution and develop and validate a population-specific TBW equation for urban South Asian women.

SUBJECTS AND METHOD

Data of 80 urban Sri Lankan women (30-45 years) were used for this analysis. Body composition was assessed by (2)H2O dilution (reference) and BIA. Available BIA equations were assessed for validity. A new TBW equation was generated and validated.

RESULTS

Direct BIA measurements and other equations did not meet validation criteria in predicting TBW. TBW by the new equation (TBW = 3.443 + 0.342 × (height(2)/impedance) + 0.176 × weight) correlated (p < 0.001) with TBW by reference method. TBW using the new equation was not significantly different (25.30 ± 2.4 kg) from the reference (25.32 ± 2.7 kg).

CONCLUSION

Direct use of TBW by instrument and existing equations are less suitable for this population. The new TBW equation is suitable for body composition assessment in urban South Asian women.

Body fat assessment in Sri Lankan adolescent girls; development of a simple field tool

BACKGROUND

Development of accurate, simple measures of body fat is essential in developing countries due to the rising prevalence of overweight and obesity. Application of skin-fold thickness (SFT) to body fat prediction equations is an inexpensive method suitable for field settings.

AIM

To determine percentage fat mass (%FM) of Sri Lankan adolescent girls using Fourier Transform Infrared spectrometry (FTIR) as a reference method and develop a SFT-prediction equation to estimate %FM.

METHODS

Weight, height and SFT were measured and %FM determined by FTIR in 131 adolescent, post-menarcheal girls (15-19 years). SFT-measurements were applied to available body composition equations for validation in the population. A new equation for %FM was derived and validated.

RESULTS

Mean %FM (FTIR) was 19.13 ± 8.2.Selected body composition prediction equations over-estimated %FM. The multiple regression procedure yielded a final equation consisting of two anthropometric and one demographic variable, % FM = 9.701 - (0.460)* age+(0.640)*TricepsSFT+(0.583)*Supra-iliacSFT.

CONCLUSIONS

Existing SFT prediction-equations are unsuitable for predicting %FM in this population. The new equation utilizing one peripheral and one truncal skin-fold, is appropriate for prediction of %FM in this population and may be applicable to other South Asian/Asian-Indian adolescents following validation.