Interindividual variability in sleeping metabolic rate in Japanese subjects

Basal metabolic rate (BMR) or sleeping metabolic rate (SMR) is the largest component of total energy expenditure (EE). An accurate prediction of BMR or SMR is needed to accurately predict total EE or physical activity EE for each individual. However, large variability in BMR and SMR has been reported.

This study was designed to develop prediction equations using body size measurements for the estimation of both SMR and BMR and to compare the prediction errors with those in previous reports.

We measured body size, height, weight and body composition (fat mass and fat-free mass) from skinfold thickness in adult Japanese men (n=71) and women (n=66). SMR was determined as the sum of EE during 8 h of sleep (SMR-8h) and minimum EE during 3 consecutive hours of sleep (SMR-3h) measured using two open-circuit indirect human calorimeters. BMR was determined using a human calorimeter or a mask and Douglas bag.

The study population ranged widely in age. The SMR/BMR ratio was 1.01+/-0.09 (range 0.82-1.42) for SMR-8h and 0.94+/-0.07 (range 0.77-1.23) for SMR-3h. The prediction equations for SMR accounted for a 3-5% larger variance with 2-3% smaller standard error of estimate (SEE) than the prediction equations for BMR.

SMR can be predicted more accurately than previously reported, which indicates that SMR interindividual variability is smaller than expected, at least for Japanese subjects. The prediction equations for SMR are preferable to those for BMR because the former exhibits a smaller prediction error than the latter.