Body composition and physical activity patterns of Indonesian elderly with low body mass index

Body composition and physical activity of institutionalised elderly were studied. Forty elderly subjects were divided into two groups according to their body mass index (BMI). One group (n=20) had BMI < 17 kg/m2 (low BMI) and was defined as having chronic energy deficiency (CED), and the other group (n=20) had BMI values between 22.0 to 25.0 kg/m2 (BMIs generally regarded as healthy). Body composition was measured using skinfold thicknesses and bioelectrical impedance analysis (BIA). The Durnin and Womersley1 equation was used to estimate fat mass (FM) from the sum of four skinfold thicknesses, namely biceps, triceps, subscapular and suprailiac. With BIA, two formulae were adopted to calculate fat free mass (FFM); they were the Lukaski2 and Deurenberg3 equations. These three formulae were compared. The physical activity level (PAL) was estimated on the basis of recorded daily physical activity patterns, and calculation of energy expenditure was based on a report by FAO/WHO/UNU4. Skinfold assessment provided the highest value for FM estimation, and BIA using Deurenberg's3 equation (BIA-H) gave the lowest value. The average of FM obtained by the three methods in elderly with low and normal BMI were 4.9 ± 2.5 kg and 16.7 ± 3.2 kg, respectively. The discrepancy between Lukaski2 and Deurenberg3 equations was less as FM increased. The elderly with low BMIs had very low fat mass. Nevertheless, thin elderly had the same level of physical activity (1.3 x BMR) as those with apparently healthy BMIs. The BMI cut off point to define CED was not sensitive enough to detect any physical consequences of low BMI in Indonesian elderly as this may reflect PALs which are overall very low. Comparable investigation of non-institutionalised elderly is needed. This study is the first to assess the functional significance of BMI in Southeast Asian elderly.