title: Influence of aerobic capacity, body composition, and thyroid hormones on the age-related decline in resting metabolic rate.
abstract: It has been suggested that changes in fat-free weight may not fully explain the decline of resting metabolic rate (RMR) that occurs with aging. We therefore examined the hypothesis that a reduction in maximal aerobic capacity (VO2max) may partially explain the lower RMR in older men, after accounting for differences in fat-free weight and fat weight. We also considered differences in energy intake and plasma thyroid hormones as possible modulators of the age-related decline in RMR in men. Three-hundred healthy men (aged 17 to 78 years) were characterized for: (1) RMR (kcal/min) from indirect calorimetry; (2) body composition from underwater weighing; (3) maximal aerobic capacity from a test of VO2max; (4) plasma thyroid hormones (total triiodothyronine [T3], free T3, total thyroxine [T4], and free T4); and (5) estimated energy intake (kcal/d) from a 3-day food diary. A curvilinear decline of RMR with age was found (P less than .01), in which no relationship was found in men less than 40 years of age (r = .10, slope = 0.002 kcal/min/yr), whereas in men older than 40 years, RMR was negatively related to age (r = -.52, slope = -0.008 kcal/min/yr). After statistical control for differences in fat-free weight and fat weight, a negative relationship between age and RMR persisted (partial r = -.30, P less than .01). It was only after control for fat-free weight, fat weight, and VO2max (partial r = -.10, P greater than .05) that no association between age and RMR was noted.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, College of Medicine, University of Vermont, Burlington 05405.
authors.forename: E T
authors.initials: ET
authors.lastname: Poehlman
authors.forename: E M
authors.initials: EM
authors.lastname: Berke
authors.forename: J R
authors.initials: JR
authors.lastname: Joseph
authors.forename: A W
authors.initials: AW
authors.lastname: Gardner
authors.forename: S M
authors.initials: SM
authors.lastname: Katzman-Rooks
authors.forename: M I
authors.initials: MI
authors.lastname: Goran
mesh_terms: D000293:Adolescent; D000328:Adult; D000332:Aerobiosis; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001481:Basal Metabolism; D001823:Body Composition; D015331:Cohort Studies; D002149:Energy Intake; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D010807:Physical Endurance; D013223:Statistics as Topic; D013963:Thyroid Hormones / Q000097:blood*
chemical_list: D013963:Thyroid Hormones