In short:
- Muscle mass is one of the biggest influences on resting energy expenditure — muscle tissue uses energy even while you rest.
- Muscle mass declines with age (sarcopenia), which slows metabolism and increases health risks.
- Strength training and enough protein help maintain muscle mass and keep metabolism active.
Muscle mass and metabolism are inseparably linked: the more active muscle tissue your body has, the more energy it burns even at complete rest. Muscles are not just a tool for movement but also the body’s largest metabolically active tissue. In this overview, we look at how muscle mass works as an engine and why maintaining it is an investment in longevity.
How do muscle mass and metabolism work together?
Muscle mass and metabolism are linked mainly through resting energy expenditure (RMR) — the amount of energy the body uses to sustain vital functions at rest. Skeletal muscle is one of the most important determinants of resting energy expenditure: studies show that muscle tissue metabolism explains a significant share of the differences in RMR between individuals (Zurlo, 1990). Skeletal muscle makes up roughly 40% of the body weight of a healthy adult and serves as the body’s main storage system for amino acids and glucose (Wolfe, 2006).
Because muscle tissue is more metabolically active than fat tissue, more muscle mass also means a higher baseline energy expenditure. That is why maintaining muscle matters for both weight and health — read more about how your own muscle mass is the best fat burner.
Why does muscle mass decline with age?
From middle age onward, muscle mass gradually begins to decline — a process called sarcopenia. The updated consensus of the European working group (EWGSOP2) defines sarcopenia as a progressive loss of muscle strength and mass that increases the risk of falls, functional decline and early mortality (Cruz-Jentoft, 2019). Losing muscle mass slows metabolism and can set off a vicious circle: less muscle means lower energy expenditure and often less physical activity as well.
The World Health Organization emphasizes that maintaining muscle strength and mobility is one of the cornerstones of healthy aging — you can find more detail in WHO’s healthy aging materials. The good news is that sarcopenia is not inevitable: regular training can significantly slow the loss. See also how to keep your life’s engine in peak condition.
How can you maintain muscle mass and metabolism?
The most effective tool for maintaining muscle mass and metabolism is strength training. Systematic reviews show that resistance training increases muscle strength and mass and improves several health markers at any age (Westcott, 2012). The American College of Sports Medicine (ACSM) recommends that adults do at least two strength training sessions a week, covering the body’s major muscle groups.
In addition to training, adequate protein intake is important, as it provides the building material for muscle recovery and growth. A combined approach — regular strength training and enough protein — supports the long-term maintenance of muscle mass. For a systematic foundation for planning your training, see building a training program: the complete guide.
Does muscle mass affect lifespan?
Studies suggest that greater muscle mass is associated with better survival. An analysis conducted among older adults found that a higher muscle mass index was associated with lower all-cause mortality (Srikanthan, 2014). This alone does not prove causality, but it fits the broader picture in which muscle tissue supports metabolic health, blood sugar regulation and physical independence in older age. Muscle’s role in longevity is so significant that it can be seen as the body’s natural protective layer — this is explained in more detail in your own muscle mass is the best source of youthfulness.
References
- Zurlo F, Larson K, Bogardus C, Ravussin E (1990). Skeletal muscle metabolism is a major determinant of resting energy expenditure. Journal of Clinical Investigation. PMID: 2243122
- Wolfe RR (2006). The underappreciated role of muscle in health and disease. American Journal of Clinical Nutrition. PMID: 16960159
- Cruz-Jentoft AJ, Bahat G, Bauer J, et al. (2019). Sarcopenia: revised European consensus on definition and diagnosis (EWGSOP2). Age and Ageing. PMID: 30312372
- Westcott WL (2012). Resistance training is medicine: effects of strength training on health. Current Sports Medicine Reports. PMID: 22777332
- Srikanthan P, Karlamangla AS (2014). Muscle mass index as a predictor of longevity in older adults. American Journal of Medicine. PMID: 24561114
Frequently asked questions
Does more muscle mass speed up metabolism?
Yes, to a moderate degree. Muscle tissue is metabolically active and burns energy even at rest, so greater muscle mass raises resting energy expenditure (Zurlo, 1990).
How much does muscle mass decline with age?
Muscle mass usually starts to decline from middle age, and the decline accelerates later in life. This process is called sarcopenia, and training can slow it significantly (Cruz-Jentoft, 2019).
What kind of training helps maintain muscle mass?
The most effective is strength training, also known as resistance training, which the ACSM recommends at least two times a week for the major muscle groups (Westcott, 2012).
Is muscle mass linked to a longer lifespan?
Observational studies link a higher muscle mass index to lower mortality among older adults, although this is not proof of causality on its own (Srikanthan, 2014).
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