"IDEAL" Aging Is Associated with Lower Resting Metabolic Rate: The Baltimore Longitudinal Study of Aging

Objectives To assess the associations among age, health status, and resting metabolic rate (RMR) in a large population of older adults. Design Cross-sectional analysis. Setting Community-dwelling volunteers from the Baltimore Longitudinal Study of Aging (BLSA). Participants Persons aged 40 to 96 (mean 68.2 +/- 11.0) who underwent a comprehensive physical examination, cognitive assessment, RMR testing, body composition assessment, and physical function testing during a 3-day clinic visit (N=420). Measurements Participants were assigned to Insight into the Determination of Exceptional Aging and Longevity (IDEAL) or non-IDEAL categories based on health status. IDEAL participants were defined according to the absence of physical and cognitive impairments, chronic conditions and comorbidities, and blood profile abnormalities. A three-stage linear regression model was used to assess the relationship between RMR and age, using IDEAL classification as a predictor and adjusting for sex and body composition. Results Resting metabolic rate averaged 1,512.4 +/- 442.9kcal/d and was lower with older age (beta=-8.55, P<.001). After adjusting for age, sex, and body composition, RMR was 109.6kcal/d lower in IDEAL than non-IDEAL participants (P<.005). Conclusion Individuals who are fully functional and free of major medical conditions have lower RMR than those with disease and functional impairments. These findings suggest that health status plays a role in energy use and regulation independent of age and body composition and that elevated RMR may be a global biomarker of poor health in older persons.