When it comes to aging, muscle health is proving to be the canary in the coal mine. While traditional metrics such as body mass index (BMI) are perhaps useful at a population level, at an individual level they don't provide information about the composition of that body mass. Instead, emerging evidence suggests that the quantity and quality of muscle is a major determinant of morbidity and mortality.
To learn more, Medscape contributor Akash Goel, MD, spoke with Rebecca Lee, MS, RDN, LDN, CNSC, whose work focuses on pediatrics and international nutrition, and Patricia Sheean, PhD, RD, an associate professor in the department of Applied Health Sciences in the Parkinson School of Health Sciences and Public Health at Loyola University, as well as a registered dietitian with over two decades of expertise in clinical nutrition epidemiology.
This conversation explores the role of sarcopenia, or decreased muscle mass, in health outcomes, as well as the role that nutrition and diet can have in optimizing muscle health. Lee and Sheean responded in tandem to the questions below, which have been condensed and edited for clarity.
Causes and Consequences
What is sarcopenia?
Sarcopenia is a clinical condition characterized by low muscle mass and low muscle strength. One of the hallmark features of sarcopenia is the loss of skeletal muscle without disturbance to the adipose tissues.
Is sarcopenia largely driven by nutrition, lifestyle, or genetic factors?
Loss of muscle mass is a natural effect of aging. Humans begin to lose muscle mass starting in our 30s and 40s.
Sarcopenia is a type of muscle atrophy with multiple causes, which often overlap. It is functionally characterized by muscle weakness and phenotypically characterized by muscle loss. It can occur as a consequence of disease (cancers, chronic disorders), malnutrition, inactivity, or a combination of these factors.
Because these events generally occur in older individuals, we tend to think this is predominantly prevalent in older individuals. However, it can and is observed in younger individuals as well.
Can you share some of the evidence linking sarcopenia independently to adverse clinical outcomes, such as falls, hospitalization, and mortality?
Sarcopenia has been widely studied in individuals with cancer and is considered an independent predictor of poor physical function, lower quality of life, surgical complications, cancer progression, and reduced survival.
In a systematic review and meta-analysis on the short-, middle-, and long-term consequences of sarcopenia in a mix of older individuals, Beaudart and colleagues report higher mortality (pooled odds ratio [OR], 3.596; 95% CI, 2.96-4.37). Those older than 79 years of age were especially likely to experience an increased functional decline (pooled OR, 3.03; 95% CI, 1.80-5.12), a higher rate of falls, and a higher incidence of hospitalizations.
Diagnostic Difficulties and Tips
Is the number of individuals suspected of having sarcopenia underdiagnosed or undiagnosed?
As sarcopenia is a complex condition brought on with the onset of multiple factors, it is often undiagnosed and undertreated in day-to-day clinical practice. Because of this, the objective clinical markers and cut-off measurements required to diagnose this condition are also challenging to ascertain. Therefore, pinpointing the number of individuals affected by sarcopenia is difficult.
Why is BMI not considered an effective measure for identifying those suspected with sarcopenia?
BMI is a tool that gained momentum in the late 1990s. It was encouraged to help primary care physicians and other clinicians quickly identify and address obesity in their patients. It is a crude tool that theoretically serves as a proxy measure of total adiposity. However, while quick and easy to calculate, it is important to highlight that BMI tells clinicians nothing about regional adiposity (pear vs apple shape) or muscle mass.
We now recognize that sarcopenia occurs across the BMI spectrum and is not restricted to those who are underweight (ie, BMI < 18.5). Sarcopenia can and does occur in individuals with obesity. This condition is deemed "the double metabolic burden" by Dr Carla Prado, a Canadian body composition scientist and early pioneer in this field.
Individuals have all the health effects of excess adiposity, coupled with the adverse risks of sarcopenia. Sarcopenia cannot be detected simply by looking at the patient and is thus underdiagnosed or recognized.
The European Working Group on Sarcopenia in Older People 2 (EWGSOP2) consensus statement defines the suspicion of sarcopenia as deficiency in muscle strength, which is confirmed by the presence of either low muscle quantity or quality. Can you discuss these criteria?
There is a widely held belief that sarcopenia is simply decreased muscle mass. However, the EWGSOP2 group highlighted the importance of muscle quality, specifically muscle strength. This recommendation recognizes the challenges of measuring muscle mass in the clinical setting and suggests several measures of muscle function, including tests that can be done in the office or clinic space. These include sit-to-stands, handgrip strength, and gait speed.
Practically speaking, sit-to-stands are probably the easiest to administer. All clinicians need are a standard chair and a timer (now found on every mobile phone.)
Additionally, there is now a sarcopenia screener (five questions) that could be incorporated into office or clinic intake forms.
If advanced imaging and diagnostics are not available, how can physical examination be helpful?
In the absence of technological devices, comprehensive physical examination of muscle health is easily administered across multiple care settings and does not require rigorous training or extra technicians.
Nutrition-focused physical examinations take a closer look at muscle status in regions such as the temples, clavicles, acromion, interosseous, quadriceps, and calves.
Muscle groups in these areas, especially the upper half of the body, are more sensitive to the effects of sarcopenia. Although this examination is subjective data, it can be used to build a case for further workup for sarcopenia diagnosis.
We recommend also utilizing anthropometric measurements (such as calf circumference), and muscle strength and performance tests (sit-to-stand, handgrip strength) to complement physical examination findings.
Screening Considerations
What type of nutritional history should be taken from these patients, and how should dietary protein quantity and quality be assessed?
A nutritional history should include a detailed diet recall inquiring about types of foods consumed, frequency and consistency of meal patterns, and variety of food groups. In addition, questions regarding weight history and activity patterns are very important. Unintentional weight loss and "not feeling up to my usual activities" are risk factors for sarcopenia, as well as overall nutritional decline.
Providers can enlist the help of a registered dietitian to complete a comprehensive nutrition assessment; however, not all clinicians have ready access to a registered dietitian and are responsible for this type of care and advice.
It is important to encourage patients to eat a variety of foods, especially those of varying colors.
Dietary protein quality and quantity will vary based on patient medical conditions and activity level. Providers should encourage at least one good protein source with each meal and/or snack from both animal and plant sources. If a patient follows a vegetarian or vegan dietary pattern, encourage incorporation of soy- or pea-based proteins.
For individuals who do screen positive for sarcopenia, what exercise and diet regimens would you recommend? The standard US recommended dietary allowance for dietary protein is 0.8 g/kg of body weight. My understanding is that this is the bare minimum.
To clarify, simply eating the recommended protein amount per day will not build muscle, nor will this overcome the underlying causes of sarcopenia. Promotion of muscle growth requires consumption of adequate calories and resistance exercise training. If individuals eat less than what they require and do not have adequate protein, they will waste muscle to meet basic energy demands.
Consuming a balanced diet of carbohydrates, healthy fat, and adequate, high-biological-value protein is the goal. This is why we recommend an interdisciplinary approach to address sarcopenia, as there are multiple factors that require attention.
Protein requirements will vary based on body weight, medical history, acute or chronic conditions, and activity level. There are no established thresholds for protein requirements for individuals with sarcopenia. For individuals with a history of weight loss and/or adults aged 65 years or older, an ideal goal is to aim for at least 1 gram of protein for every kilogram of body weight. This can also go as high as 1 gram per pound of body weight, but that may not be realistic for some and contraindicated in certain medical conditions.
We do strongly recommend that anyone who is looking for more guidance with their individualized protein needs should see a qualified professional.
What is the role of branched-chain amino acids (BCAA) in building muscle mass?
The role of BCAA in building muscle has not yet been determined. We need to be cautious of trendy dietary advice and make recommendations with scientific framing.
It is also critical to recognize alterations in protein metabolism and efficiency in the context of age and illness. When patients are acutely ill, the stress response prohibits them from anabolism and optimally utilizing amino acids for muscle mass. This is worse in older individuals, especially as hormone levels fall. The role of testosterone on muscle mass and health is undeniable.
As of now, we know that well-rounded nutritional intake is key to optimizing health. Focusing on a specific type of amino acid is not practical or realistic. As humans, we don't consume food like this, unless it is in supplement form. The goal is always to recommend that our patients eat whole foods, closest to their most natural form.
A recent study from investigators at Purdue University demonstrated higher bioavailability of animal-based protein sources when compared with plant-based protein sources. Do you have a recommendation on how protein should be partitioned between various sources?
We should always advise patients or clients to eat a variety of foods, including varied protein sources. We need to personalize our messaging to take into consideration not only personal taste preference, but also religious practices, affordability, medical conditions, and the climate. For a growing sector of the population, eating animal-based protein is simply impractical, unaffordable, unsustainable, and unethical.
Parting Advice
In medicine, do you think we should be as concerned if a patient is undermuscled as we are if they are overweight?
Because decreased muscle function predisposes individuals to the host of previously mentioned adverse events, identifying "undermuscled" patients is clinically relevant. Incorporating the SARC-F screening tool questions into a patient history or augmenting a physical exam to focus on nutritional concerns are simple measures to address this condition in patients at risk.
Is there anything else you would like to comment on?
This is a rapidly expanding area of clinical research. Identifying methods to combat sarcopenia remains extremely challenging.
It is important to acknowledge that people at risk for sarcopenia are not going to respond to exercise or other treatments (dietary protein) like their healthy counterparts. There are a host of etiologies that lead to muscle wasting. Identifying and correcting them are foundational.
Additionally, future studies need to consider the practical nature of their findings and the needed resources (personnel, equipment, costs) for success. Not all people have weights and resistance bands or the knowledge and confidence to exercise.
Further, clinicians need to make sound recommendations to their patients considering what is truly achievable and sustainable. Simply talking at the patient and telling them what they should do will not cure this disease.
Dr Akash Goel is a clinical assistant professor of medicine (gastroenterology and hepatology) at Weill Cornell. His work has appeared on networks and publications such as CNN, The New York Times, Time Magazine, and Financial Times. He has a deep interest in nutrition, food as medicine, and the intersection between the gut microbiome and human health.
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Cite this: Treating Sarcopenia Requires a Muscular Approach - Medscape - Nov 14, 2023.
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