What Is Sarcopenia?

Reviewed by SOMA HEALTH's Medical Research Team

Sarcopenia is the progressive, age-related loss of skeletal muscle mass, strength, and function. It is a recognized medical condition, not simply a cosmetic change, and it has a well-studied link to how muscle mitochondria age. This guide explains what it is, why it happens, and the evidence-based steps that support muscle as the years add up.

A note before we start: sarcopenia is a diagnosable condition. This page is educational and structure/function in nature. It is not a treatment plan, and no supplement described here is intended to diagnose, treat, cure, or prevent sarcopenia or any disease. If you are concerned about muscle loss, weakness, or falls, please see your doctor for assessment.

Defining sarcopenia

The term sarcopenia combines the Greek roots for flesh and loss. Clinically, it describes an accelerated decline in muscle beyond what is expected from normal aging alone, to the point where strength and physical performance are affected. European consensus groups (the EWGSOP) revised the definition in 2019 to put low muscle strength at the center of diagnosis, with low muscle quantity or quality used to confirm it, and poor physical performance marking more severe cases.

In practice, clinicians may screen with simple tools and then measure grip strength, a sit-to-stand test, gait speed, or muscle mass using techniques such as DXA or bioimpedance. No single number defines everyone, which is part of why diagnosis belongs with a healthcare professional rather than a self-assessment.

How common is it, and when does it start?

Muscle mass tends to peak in early adulthood and then decline gradually, with the pace often quickening from around the fifth and sixth decades of life and accelerating further later on. Because definitions and measurement methods differ between studies, reported prevalence varies widely, but sarcopenia becomes meaningfully more common with advancing age and is associated with a higher risk of falls, frailty, and loss of independence. The encouraging counterpoint is that muscle remains adaptable across the lifespan, which is why intervention studies focus so heavily on training and nutrition.

Why muscle is lost: the drivers

Sarcopenia is multifactorial. Several changes tend to accumulate together with age:

Fewer and less responsive muscle fibers. The number of motor units declines, type II (fast-twitch) fibers shrink preferentially, and muscle becomes less responsive to the anabolic signal from dietary protein, a phenomenon sometimes called anabolic resistance.

Hormonal and inflammatory shifts. Age-related changes in hormones and a low-grade rise in background inflammation, sometimes termed inflammaging, tilt the balance away from building muscle and toward breaking it down.

Reduced activity. Lower daily movement and less resistance loading remove the very stimulus muscle needs to maintain itself, creating a self-reinforcing cycle.

Mitochondrial decline. This is the thread most relevant to our work, and it deserves its own section.

The mitochondrial link

Skeletal muscle is one of the most mitochondria-dense tissues in the body, because contraction is energetically expensive. Research consistently finds that aging muscle shows reduced mitochondrial oxidative capacity, accumulation of damaged mitochondria, and a slowdown in the quality-control processes that normally keep the network healthy. A widely cited human study reported that mitochondrial oxidative capacity and NAD+ biosynthesis were reduced in sarcopenia across ethnic groups, reinforcing the idea that muscle energetics are part of the picture rather than a bystander.

The relevant quality-control process is mitophagy, the targeted recycling of worn-out mitochondria, which pairs with the building of new mitochondria to keep muscle energetics efficient. Our explainers on what mitophagy is and mitochondrial health go deeper. Because muscle depends so heavily on this build-and-recycle cycle, interest has grown in whether supporting it might complement the well-established interventions of exercise and protein.

Where urolithin A enters the conversation

Urolithin A is a gut postbiotic your microbiome can make from ellagitannins in pomegranates, walnuts, and berries, though not everyone converts it efficiently. It is studied mainly for its role in mitophagy, the recycling side of mitochondrial renewal, which is why muscle has been a focus of the human trials.

Here the human evidence is directly relevant, and it should be read carefully. Singh and colleagues (2022, Cell Reports Medicine) tested 500 mg and 1,000 mg per day over four months in middle-aged adults and reported effects on muscle strength and aspects of exercise performance. Liu, D'Amico and colleagues (2022, JAMA Network Open) reported improved muscle endurance in older adults over roughly four months. The first-in-human trial by Andreux and colleagues (2019, Nature Metabolism) established safety and tolerability up to 1,000 mg per day and a mitochondrial gene-expression signature. A 2024 randomized trial in the Journal of the International Society of Sports Nutrition examined an eight-week protocol in resistance-trained men. These are structure/function findings in generally healthy adults; they are not studies of treating diagnosed sarcopenia.

The preclinical foundation is broader but earlier-stage. Ryu and colleagues (2016, Nature Medicine) showed that urolithin A induced mitophagy and improved muscle measures in rodents, alongside lifespan extension in the worm C. elegans. That animal work motivated the human trials but does not by itself prove clinical benefit in people. For a full trial-by-trial breakdown, see our clinical studies page, and for muscle specifically, urolithin A for muscle.

What is proven to help

Resistance training

The single most effective, evidence-backed intervention against age-related muscle loss is progressive resistance training. Muscle responds to load at every age, and even previously sedentary older adults can gain strength and function with a structured program. Aerobic work complements this by supporting mitochondrial capacity, which ties back to markers like VO2 max.

Protein and overall nutrition

Because aging muscle is less responsive to protein, adequate intake spread across the day, along with sufficient calories and micronutrients, becomes more important, not less. Many older adults under-consume protein relative to what supports muscle maintenance.

Staying active and addressing risk factors

Reducing sedentary time, managing chronic conditions with your doctor, and addressing vitamin and hormonal deficiencies where present all support the muscle you have. These fundamentals do the heavy lifting; supplements sit on top of them, not in place of them.

Honest limitations

Human urolithin A research is still emerging, as a 2024 systematic review in Ageing Research Reviews concluded. The muscle trials to date have generally studied healthy or resistance-trained adults over months, not people diagnosed with sarcopenia, and results reflect structure/function outcomes rather than treatment of a condition. Individual response varies, in part because of microbiome differences. None of this replaces the proven core of resistance training and nutrition, and none of it is a substitute for medical care.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This guide is educational and is not a substitute for advice from a qualified healthcare provider.