Many people associate muscle with strength, athletic performance, and physical appearance. While all of that is correct, there’s more to the story. Muscle tissue is metabolically active, meaning it helps regulate blood sugar, supports movement, and contributes to your ability to remain independent as you age.
Muscle mass naturally declines with age. Research suggests that adults lose approximately 3% to 8% of muscle mass per decade after age 30, with losses accelerating after 60. [1]
The challenge is that many people don’t know how much muscle they have or whether they’re maintaining it. A bathroom scale can tell you how much you weigh, but it doesn’t tell you whether changes in your weight reflect gains or losses in fat or muscle.
At Biograph, we view muscle mass as an important healthspan asset. Understanding how to measure muscle mass through tools such as DEXA, and evaluating strength alongside it, can help us identify changes early and develop a more targeted approach to preserve it.
Why skeletal muscle is an essential metabolic organ
Skeletal muscle does much more than help you climb stairs or lift heavy objects. It’s also one of the body’s largest sites for glucose uptake and acts as an endocrine organ. During exercise, contracting muscles release proteins called myokines that send signals to other parts of your body, helping regulate processes such as metabolism and inflammation.
Glucose disposal and insulin sensitivity
After you eat, your pancreas releases insulin, which helps muscle cells absorb glucose (sugar) from your bloodstream. That glucose can then be used for energy or stored as glycogen for later use.
After a meal, skeletal muscle accounts for approximately 80% of the body’s glucose uptake, making it central to blood sugar regulation and insulin sensitivity. [2] [3]
Maintaining muscle is critical for supporting metabolic health. Resistance training, for example, can improve insulin sensitivity and glucose regulation, even when it doesn't move the needle on the scale all that much.
Myokines: How muscle communicates with the rest of your body
As muscles contract during exercise, they release signaling molecules called myokines, which communicate with other tissues and organs.
Researchers are studying how myokines, including interleukin-6, irisin, and brain-derived neurotrophic factor (BDNF), affect inflammation, metabolism, and other physiological processes. [4]
Sarcopenia, fall risk, and frailty
As muscle mass and strength decline with age, some people develop sarcopenia, a condition characterized by reduced muscle strength and low muscle quantity or quality. Sarcopenia can make everyday activities more challenging, increase your fall risk, and contribute to frailty and reduced or loss of independence.
The long-term health implications are significant. A systematic review and meta-analysis published in PLOS ONE found that adults with low skeletal muscle mass had a 57% higher relative risk of all-cause mortality compared with those with normal muscle mass. [5] While this finding doesn’t establish causation, it underscores the importance of preserving muscle as we age.
How to measure muscle mass accurately
A body-composition assessment can help distinguish fat from lean tissue, while strength and performance testing show how well your muscles function. Here’s what the different measurement tools can tell clinicians.
DEXA body composition scans
A DEXA scan, or dual-energy X-ray absorptiometry, is one of the most established clinical methods for evaluating body composition.
Using low-dose X-rays, DEXA measures bone mineral density and estimates fat mass and lean soft tissue, including how these tissues are distributed throughout the body. It can help track body-composition changes as you age, go through hormonal transitions such as perimenopause, or begin an exercise program.
Importantly, DEXA measures lean soft tissue rather than skeletal muscle directly. Because lean tissue also includes water and other nonfat components, the results provide an estimate of muscle quantity rather than an exact measurement.
Appendicular lean mass and ALMI
One of the most relevant DEXA measurements is appendicular lean mass (ALM), which represents the lean soft tissue in your arms and legs.
Because your limbs contain substantial skeletal muscle, ALM is commonly used to estimate muscle quantity when evaluating sarcopenia. Clinicians may also calculate an appendicular lean mass index (ALMI) by dividing ALM in kilograms by height in meters squared.
Tracking these measurements over time can help identify changes in lean tissue, particularly during weight loss or as you age.
Many consumer smart scales use bioelectrical impedance analysis (BIA), which passes a small electrical current through your body to estimate both your fat and lean mass content.
While convenient, BIA results can fluctuate based on hydration, recent meals, exercise, and the device that’s used. A change in your smart scale’s reported muscle mass doesn’t necessarily reflect an actual change in muscle tissue.
DEXA generally provides a more reliable picture of body composition than consumer smart scales, though factors such as hydration can still sway the results. For the most meaningful comparisons over time, it’s best to have your scans performed under similar conditions.
Why muscle quality matters as much as quantity
Knowing how much muscle you have doesn’t necessarily tell us how well it functions. Two people with similar appendicular lean mass can have very different levels of strength, power, and mobility.
That’s why functional assessments also matter. Grip strength can help evaluate muscular strength, while chair-rise tests and walking speed can help reveal your functional fitness, or ability to do everyday movements with relative ease.
Muscle power, or how quickly you can generate force, also becomes increasingly important with age. It’s what helps you catch yourself if you trip or balance as you get up from a chair.
How Biograph evaluates muscle mass and musculoskeletal health
At Biograph, we assess muscle health through body-composition imaging, strength testing, and movement analysis.
Our DEXA scan measures lean tissue, fat distribution, and bone density, while grip-strength testing and DARI 3D motion analysis evaluate strength, balance, and mobility. We also assess VO2 max to get a better idea of your cardiorespiratory fitness.
Together, these findings help us identify areas that need attention so we can develop a personalized strategy to preserve your muscle health and physical function as you age.
Consider a 54-year-old woman who loses 25 pounds over six months while taking a GLP-1 medication, but is experiencing fatigue and declining strength.
A DEXA scan reveals that a substantial portion of her weight loss came from lean tissue, and her appendicular lean mass is low. While DEXA can’t determine exactly how much muscle she’s lost, these findings suggest that preserving muscle should become a greater priority.
Her physician can then reassess her protein intake, resistance training, and other aspects of her weight-management plan to help minimize even more lean tissue loss while on the weight-loss medication.
How to build and preserve muscle as you age
Age-related muscle loss isn’t entirely inevitable. Skeletal muscle remains responsive to exercise and nutrition well into older adulthood, and there are several strategies you can follow to help preserve it.
Prioritize resistance training
Resistance training is one of the most effective ways to maintain and build muscle. Exercises using free weights, machines, resistance bands, or your own body weight can help maintain your current strength and muscle mass.
For most adults, aim to train major muscle groups at least twice per week. Progressive overload, or gradually increasing the challenge as your body adapts, can help you increase both your muscle mass and strength. How quickly you progress should depend on your fitness level, medical history, and recovery regimen.
Eat enough protein and total calories
Protein provides the amino acids needed to build and repair muscle, while adequate calorie intake supports training and recovery.
How much protein you specifically need depends on many factors such as your age, body size, activity level, and medical history. For instance, older adults and people who regularly strength train may benefit from higher protein intakes than the standard recommended dietary allowance.
Adequate nutrition is especially important during periods of weight loss, when your body can lose both fat and lean tissue. Combining sufficient protein intake with resistance training can help minimize muscle loss, including for people taking weight-management medications.
Resistance training shouldn’t replace aerobic exercise, which supports cardiovascular and metabolic health. Balance and mobility exercises can also help maintain physical function as you age.
Sleep and recovery are equally important, giving your muscles time to adapt to training. Together, these habits can help preserve the strength and physical capacity needed to stay active and independent.
The bottom line
Muscle is more than a marker of physical fitness. It plays an important role in metabolic health, mobility, and independence as you age. While some muscle loss is a natural part of aging, resistance training, adequate nutrition, and regular physical activity can help slow that decline.
But preserving muscle starts with understanding where you stand. Measuring lean mass with DEXA and assessing your strength and functional fitness can help identify changes early and guide a more personalized approach to protecting your healthspan.
Commonly asked questions about muscle as a healthspan asset
Can a DEXA scan measure muscle mass?
A DEXA scan measures lean soft tissue, fat mass, and bone mineral content. Because lean tissue includes muscle and other tissues, DEXA estimates muscle quantity indirectly rather than measuring skeletal muscle itself.
What is sarcopenia, and when does it begin?
Sarcopenia is a muscle disorder characterized primarily by reduced muscle strength, with low muscle quantity or quality helping confirm the diagnosis. Age-related muscle loss can begin in early adulthood and often accelerates later in life, but having some muscle loss doesn't automatically mean you have sarcopenia.
Why can smart scales be inaccurate for measuring muscle mass?
Most smart scales use bioelectrical impedance analysis to estimate body composition. Hydration, recent meals, exercise, and device-specific equations can affect their results, so a reported change in muscle mass isn’t necessarily a true change in skeletal muscle.
What is appendicular lean mass?
Appendicular lean mass is the total lean soft tissue measured in your arms and legs, usually using DEXA. Clinicians use it as an estimate of skeletal muscle quantity and may adjust it for height to calculate the appendicular lean mass index (ALMI).
Can you rebuild muscle mass after age 50?
Yes. Older adults can improve muscle strength and increase muscle mass through progressive resistance training, adequate nutrition, and recovery.
Dr. Michael Doney is Biograph’s Executive Medical Director, with over 20 years of experience leading clinical care and advancing a more proactive, data-driven approach to medicine.
Clinical references
Volpi E, Nazemi R, Fujita S. Muscle tissue changes with aging. Current opinion in clinical nutrition and metabolic care. 2004;7(4):405-410. doi:10.1097/01.mco.0000134362.76653.b2
Merz KE, Thurmond DC. Role of Skeletal Muscle in Insulin Resistance and Glucose Uptake. Comprehensive Physiology. 2020;10(3):785-809. doi:10.1002/cphy.c190029
Mancilla R, Krook A, Schrauwen P, Hesselink MKC. Diurnal Regulation of Peripheral Glucose Metabolism: Potential Effects of Exercise Timing. Obesity. 2020;28(S1). doi:10.1002/oby.22811
Schnyder S, Christoph H. Skeletal muscle as an endocrine organ: PGC-1α, myokines and exercise. Muscle Bone Interactions. 2015;80:115-125. doi:10.1016/j.bone.2015.02.008
Wang Y, Luo D, Liu J, Song Y, Jiang B, Jiang H. Low skeletal muscle mass index and all-cause mortality risk in adults: A systematic review and meta-analysis of prospective cohort studies. , ed.Yamada Y. PLOS ONE. 2023;18(6):e0286745. doi:10.1371/journal.pone.0286745
