0038 Consistency of Interindividual Differences in the Amplitude of Daily Energy Expenditure and Respiratory Quotient Rhythms in Healthy Adults
Conference Proceeding
Overview
abstract
Abstract; ; Introduction; We have previously reported stable, trait-like interindividual differences for average 24-hour energy expenditure (EE) and respiratory quotient (RQ), and their average levels during scheduled wakefulness and sleep. However, interindividual differences in the daily amplitude of the EE and RQ rhythms remain to be explored. The amplitude of daily rhythms is of growing interest given that reduced amplitude (e.g., body temperature, physical activity) is associated with aging and disease.; ; ; Methods; 15 healthy adults (age 23.3±3.4 mean±SD, 7 females) completed a 4-day in-laboratory protocol consisting of one habituation night and three days of living in a whole room indirect calorimeter. Participants maintained consistent 8-hour sleep schedules at their habitual times for one week and consumed an outpatient energy-balanced diet for three days before in-laboratory testing. During calorimeter days, participants remained in constant bedrest, consumed the energy-balanced diet with meals 0.5h, 4.5h, 10.5h, and 14.5h after scheduled awakening, and were provided 8h sleep opportunities. EE and RQ were measured every minute. Daily amplitude of the EE and RQ rhythms was determined using non-orthogonal spectral analysis. Mixed-model ANOVA with participant as a random factor and day as a fixed factor was performed. Intraclass correlation coefficients (ICC) were calculated to examine the stability of individual differences.; ; ; Results; A significant main effect of participant was observed for EE and RQ amplitude (both P< 0.01), whereas the main effect of day was not significant for either (P>0.75). The stability of individual differences in EE daily amplitude was almost perfect (ICC=0.90), whereas daily amplitude was moderate (ICC=0.43).; ; ; Conclusion; These findings indicate stable, trait-like interindividual differences in EE daily amplitude and less robust interindividual differences in RQ daily amplitude. Additional research is needed to understand the mechanisms contributing to these individual differences and why EE is more consistent than RQ, test for the stability of interindividual differences in other populations (e.g., aging, people with obesity), and determine their impact on physiological function.; ; ; Support (if any); National Institutes of Health (NIH/NCATS Colorado CTSA Grant Number UL1 TR001082, P30 DK048520), a Grant from Philips Incorporated, and the Undergraduate Research Opportunities Program in collaboration with the Howard Hughes Medical Institute and Biological Sciences Initiative.;
