Age-Dependent Changes in Resting Energy Expenditure (REE): Insights from Detailed Body Composition Analysis in Normal and Overweight Healthy Caucasians

Abstract

Age-related changes in organ and tissue masses may add to changes in the relationship between resting energy expenditure (REE) and fat free mass (FFM) in normal and overweight healthy Caucasians. Secondary analysis using cross-sectional data of 714 healthy normal and overweight Caucasian subjects (age 18–83 years) with comprehensive information on FFM, organ and tissue masses (as assessed by magnetic resonance imaging (MRI)), body density (as assessed by Air Displacement Plethysmography (ADP)) and hydration (as assessed by deuterium dilution (D2O)) and REE (as assessed by indirect calorimetry). High metabolic rate organs (HMR) summarized brain, heart, liver and kidney masses. Ratios of HMR organs and muscle mass (MM) in relation to FFM were considered. REE was calculated (REEc) using organ and tissue masses times their specific metabolic rates. REE, FFM, specific metabolic rates, the REE-FFM relationship, HOMA, CRP, and thyroid hormone levels change with age. The age-related decrease in FFM explained 59.7% of decreases in REE. Mean residuals of the REE-FFM association were positive in young adults but became negative in older subjects. When compared to young adults, proportions of MM to FFM decreased with age, whereas contributions of liver and heart did not differ between age groups. HOMA, TSH and inflammation (plasma CRP-levels) explained 4.2%, 2.0% and 1.4% of the variance in the REE-FFM residuals, but age and plasma T3-levels had no effects. HMR to FFM and MM to FFM ratios together added 11.8% on to the variance of REE-FFM residuals. Differences between REE and REEc increased with age, suggesting age-related changes in specific metabolic rates of organs and tissues. This bias was partly explained by plasmaT3-levels. Age-related changes in REE are explained by (i) decreases in fat free mass; (ii) a decrease in the contributions of organ and muscle masses to FFM; and (iii) decreases in specific organ and tissue metabolic rates. Age-dependent changes in the REE-FFMassociation are explained by composition of FFM, inflammation and thyroid hormones.

Eating disturbances in the elderly: A geriatric-psychiatric perspective

“…All these changes contribute to sarcopenia, which is characterized by loss of muscle strength, mass and functionality. In addition to sarcopenia, decreased fat free mass and high metabolic organ activity (heart, brain, kidney) result in reduced resting energy expenditure (REE) [34]. Furthermore, physical inactivity often seen with old age is closely related to sarcopenia and reduced REE.…”

Effect of tea catechins with caffeine on energy expenditure in middle-aged men and women: a randomized, double-blind, placebo-controlled, crossover trial

“…The intake of tea catechins with caffeine increases total energy expenditure (TEE) and fat utilization [8][9][10], and studies examining the effects of an acute single ingestion of tea catechins with caffeine report significant increases in EE compared with a placebo [9,11], but other studies report inconsistent effects of continuous tea catechin with caffeine intake on fasting resting metabolic rate (RMR) [12,13]. Moreover, although fasting RMR is known to decrease with age [14,15], previous studies mostly targeted young healthy subjects to examine the effects of tea catechin with caffeine [8][9][10][11] and there are few studies describing the effects of tea catechin intake on fasting RMR and EE after ingestion in middle-aged individuals.…”

Effects of different types of training on weight loss

“…The RMR value is also affected by the age and gender of the individual, hormone levels, circadian rhythm, body temperature, physical activity, genetics and malnutrition. In the course of aging, RMR progressively diminishes, mainly due to the reduction in the amount of skeletal muscle mass and mass of internal organs, gradual decrease of metabolic activity of individual organs as well as due to an increase in the proportion of fat mass which generally has a lower metabolic rate [7]. Gender differences in RMR values are also caused by a smaller amount of muscle mass and a higher amount of fat mass in women.…”