I'm Only in My Fifties — Why Do I Have Sarcopenia? Comparing Body Muscle-Mass Measurement Devices

A woman in her fifties walked into my clinic. If I hadn’t looked at her chart, I would have guessed she was only in her forties — the way she carried herself showed real attention to keeping in shape. Chatting during the visit, I learned she went to a fitness center regularly, walking on the treadmill or joining group yoga classes.

Lately, though, she had felt weaker than before going up and down stairs. I asked her to test her grip strength, and it was only 16 kilograms.

I ordered some tests in the clinic and told her, gently but seriously, that she might have sarcopenia.

Somewhat startled, she said: I’m only in my fifties, and I exercise regularly — why would I have sarcopenia?

Sarcopenia has many causes. Its underlying mechanisms are likely related to the following factors:

1. Aging and neuromuscular changes.

2. Related hormonal changes, such as declines in androgens, estrogens, and growth hormone, as muscle cells in the body begin to undergo apoptosis.

3. Increased insulin resistance, which affects protein synthesis and breakdown.

4. Increased chronic inflammatory mediators.

5. Insufficient daily protein and energy intake, or poor absorption.

6. Effects of chronic diseases: dementia, mood disorders, diabetes, chronic kidney disease, chronic obstructive pulmonary disease, heart failure, cirrhosis, osteoporosis, and others.

7. Long-term medication use: antidepressants, lipid-lowering drugs, and diuretics.

How is whole-body skeletal muscle mass measured?

Muscle makes up about 30 to 40% of body weight, and the limb muscles account for 70 to 80% of the body’s total muscle. Muscle is the source of physical capacity. One part of diagnosing sarcopenia is measuring appendicular skeletal muscle mass (ASM), which, through standardized adjustment, can be used to determine whether sarcopenia is present.

Countries around the world have set their own adjustment formulas for sarcopenia based on data from themselves and neighboring countries — some use ASM divided by height squared, some ASM divided by body weight, some ASM divided by BMI squared. In Asia, the standard used is ASM divided by height squared.

Muscle mass can be measured with computed tomography (CT), magnetic resonance imaging (MRI), bioelectrical impedance analysis (BIA), and dual-energy X-ray absorptiometry (DXA). MRI and CT come with concerns of high cost and radiation, respectively, and because the equipment is mostly located in hospitals, testing can be less convenient for patients. DXA can also measure bone density but involves a small amount of radiation, while BIA is quick and radiation-free, at the cost of slightly lower accuracy.

Adjust the mindset — the methods can be varied

The diet traditionally favored, built mainly around plain congee and small side dishes, often falls short of the protein the muscles need. If absorption is also inadequate, how can the body be expected to build enough muscle? Some people may feel that meat is hard to digest or causes bloating, but there are now many food products that reduce poor absorption, so that older adults can also get enough protein.

The stretching and gentle exercise that older adults tend to prefer provide relatively little muscle stimulus and cannot promote muscle growth. As we get older and muscle mass gradually declines, the goal should be to do everything possible to slow this process, rather than aging along with outdated ideas. Even at a younger age, if the muscle mass stored in youth was limited, sarcopenia may arrive earlier.

Sarcopenia is linked to many major health events and risk factors, such as falls, weight loss, fractures, disability, other chronic diseases, and recent hospitalization, which can feed back into the vicious cycle of sarcopenia.

Muscle mass may begin to decline after age 30, falling 8% per decade after 40 and 15% per decade after 70. For groups at higher risk or those who have had a major health event — for example, people who are bedridden long term, post-stroke, hospitalized for extended periods, or chronically inactive, and especially adults over 65 — sarcopenia screening can help clarify current muscle-strength status.

Beyond attention to nutrition, exercise is one of the ways studies suggest may help address muscle loss. A pre-exercise risk assessment through professional medical consultation is advisable, especially for patients with chronic diseases or on regular medication. People who don’t exercise often can start with low-to-moderate intensity and gradually increase the intensity, working toward maximal-load training.

Summary

Choosing a suitable measurement device can give an early picture of your own muscle-mass status. Paired with appropriate diet and exercise, this can help improve muscle mass, strength, and endurance. Training is really about more than strength — balance and correct posture in daily life also fall largely within the scope of exercise training, which in turn can reduce problems such as falls in older adults, insufficient muscular endurance for long walks, difficulty on stairs, and weakness when lifting heavy objects.

Further reading: Screening and diagnosis of sarcopenia