Basal metabolic rates and metabolic economy in chronic undernutrition.

Basal metabolic rates (BMR) and body composition were measured in 130 adult Indian males, selected from three socio-economic groups. Results show a significantly lower BMR in the chronically undernourished, with a greater dependence on carbohydrate as fuel in the fasted state. When expressed as per kg body weight or kg fat-free mass (FFM), the BMRs are significantly higher in these individuals. The latter observations suggest variations in the contribution of viscera and skeletal muscle to the FFM, with a relatively greater visceral to muscle mass ratio. However, on adjustment for differences in weight and FFM by means of an analysis of covariance, the chronically undernourished (both urban and rural) have significantly lower BMRs. This indicates a 'metabolic economy' in these individuals, which could be attributable in part to their significantly lower serum T3 levels. When the subjects are classified on the basis of grades of chronic energy deficiency (CED), individuals with low body mass index (BMI) (less than 17 and below) are not similar in their basal metabolism. Those individuals from good socio-economic backgrounds with access to ad libitum energy and protein intake but with low BMI have comparable BMRs to the well nourished. It may therefore be unwise to classify all individuals with low BMI 'across the board' as suffering from CED. Socio-economic scaling may be a useful addition to the present classification of CED.