Age-Related Changes in Energy Expenditure

Nikolay Botushanov; Aleksandar Botushanov; Albena  Botushanova

doi:10.3889/oamjms.2026.12051

Authors

Nikolay Botushanov Department of Endocrinology and Metabolic Diseases, Faculty of Medicine, Medical University of Plovdiv, Plovdiv, Bulgaria https://orcid.org/0000-0002-4183-5341
Aleksandar Botushanov Department of Endocrinology and Metabolic Diseases, Faculty of Medicine, Medical University of Plovdiv, Plovdiv, Bulgaria https://orcid.org/0000-0002-0011-6738
Albena Botushanova Department of Clinical Oncology, Faculty of Medicine, Medical University of Plovdiv, Plovdiv, Bulgaria https://orcid.org/0000-0003-2286-0936

DOI:

https://doi.org/10.3889/oamjms.2026.12051

Keywords:

Aging, Energy Expenditure, Resting Metabolic Rate, Thermic Effect of Food, Non-Exercise Activity, Thermogenesis

Abstract

BACKGROUND: Total Daily Energy Expenditure (TDEE) is a dynamic parameter influenced by basal metabolic rate (BMR), thermic effect of food (TEF), and activity-related energy expenditure (AEE). With aging, all components of TDEE undergo measurable declines due to changes in body composition, hormonal regulation, and physical activity. Understanding these age-related changes is critical for addressing malnutrition, sarcopenia, frailty, and metabolic diseases in older adults.

AIM: This review synthesizes current knowledge on the physiological, cellular, and behavioral determinants of energy expenditure across the lifespan, with an emphasis on elderly populations.

METHODS: A comprehensive literature analysis was conducted, including randomized controlled trials, observational cohort studies, and mechanistic research, focusing on age-related trends in BMR, TEF, AEE, non-exercise activity thermogenesis (NEAT), and organ-specific metabolic rates.

RESULTS: Aging is associated with reductions in fat-free mass (FFM) and specific metabolic rates of major organs. Mitochondrial dysfunction, decreased Na⁺/K⁺ ATPase activity, and diminished protein synthesis contribute to lower BMR. TEF declines due to reduced sympathetic responsiveness. AEE and NEAT are significantly impacted by behavioral, neurological, and structural limitations, leading to a progressive fall in total energy expenditure. Notably, higher AEE is independently associated with reduced mortality risk and better physiological resilience in older adults.

CONCLUSION: Age-related energy expenditure decline is multifactorial and partially modifiable. Preservation of physical activity and metabolic health through targeted interventions may mitigate the adverse effects of aging on energy balance and overall health.

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