Thermic effect of a meal. 1. Methodology and variation in normal young adults.

The variation in the thermic effect of a meal (TEM) was investigated in two groups of five subjects following a standard test meal. Results demonstrated a 50% lower response over 6 h, in the same subjects, when measured intermittently (protocol 2) as compared with a continuous measurement (protocol 1). The variation in TEM among occasions (measured on three occasions in each subject) was large (coefficient of variation (CV) 18.7%, P less than 0.02). However, the post-meal total energy output (CV 1.4%, P greater than 0.05), non-protein respiratory quotient (CV 1.9%, P greater than 0.05) and substrate oxidation rate were not different (P greater than 0.05) in the same individual on separate occasions. Small variations in the basal metabolic rate (BMR) from occasion to occasion (CV 2.6%) contributed to the variation in TEM. However, after allowing for the changes in BMR, variation in TEM (CV 8.6%, P greater than 0.05) was still sizeable though not statistically significant.