Muscle Wasting

Overview

Muscle wasting, also called muscle atrophy, is the loss of muscle bulk and strength, so that muscles become smaller and weaker than normal. It may affect a single limb, a group of muscles, or the whole body, and it can develop slowly over months or more quickly with serious illness. People may notice clothing fitting more loosely on an arm or leg, a limb looking thinner, or new weakness with everyday tasks.

Muscle naturally needs regular use and adequate nutrition to maintain its size. When a muscle is not used, when its nerve supply is damaged, or when the body breaks down muscle during illness or aging, wasting follows. Some causes are easily reversible with activity and good nutrition, while others reflect an underlying nerve or muscle disease that needs medical evaluation. Identifying the cause is important because it guides whether the muscle can be rebuilt.

Common Causes

Muscle wasting has several broad causes:

• Disuse: The most common cause, from prolonged bed rest, a cast or immobilization, or a sedentary lifestyle.
• Aging: Gradual age-related muscle loss known as sarcopenia (see also muscle atrophy).
• Nerve problems: Damage to the nerves supplying a muscle, as in peripheral neuropathy, carpal tunnel syndrome, or motor neuron disease such as ALS.
• Muscle diseases: Inherited or acquired conditions like muscular dystrophy.
• Chronic illness and poor nutrition: Cancer, severe infection, and malnutrition cause body-wide muscle loss.

Associated Symptoms

Muscle wasting is often accompanied by other signs that hint at the cause:

• Muscle weakness and reduced strength or grip
• A visibly thinner limb or muscle compared with the other side
• Fatigue and trouble with stairs, lifting, or rising from a chair
• Numbness, tingling, or twitching when a nerve is involved
• Unintended weight loss in illness-related wasting

Wasting that spreads, worsens quickly, or comes with twitching, swallowing or breathing difficulty, or slurred speech needs prompt medical evaluation.

Diagnosis & Evaluation

Finding the cause usually involves several steps:

• History and exam: Reviewing activity levels, illnesses, and medications, and measuring muscle size, strength, reflexes, and sensation.
• Blood tests: Checking muscle enzymes, thyroid function, nutrition, and signs of inflammation or other disease.
• Nerve and muscle tests: Electromyography (EMG) and nerve conduction studies assess nerve and muscle function.
• Imaging or biopsy: MRI or, occasionally, a muscle biopsy when a specific muscle or nerve disease is suspected.

Depending on findings, you may be referred to a neurologist or other specialist.

Treatment & Management

Treatment depends on the cause, and disuse-related wasting is often reversible:

• Exercise and physical therapy: Strengthening and resistance exercises rebuild muscle and are the foundation of recovery, especially after disuse or with aging.
• Nutrition: Adequate protein and overall calories support muscle repair; a dietitian can help in illness-related wasting.
• Treating the underlying condition: Managing the nerve disease, thyroid problem, or chronic illness driving the wasting.
• Assistive devices and supportive care: Braces, mobility aids, and occupational therapy maintain function in progressive conditions.

Even in progressive diseases, exercise and supportive care help preserve strength and independence for as long as possible.

Self-Care & Prevention

Much muscle wasting, especially from disuse and aging, can be prevented or slowed:

• Do regular strength training two or more days a week to build and maintain muscle.
• Stay physically active overall, and avoid long periods of inactivity or bed rest when possible.
• Eat enough protein and calories to support muscle maintenance, particularly as you age.
• Move during recovery from illness or injury as soon as it is safe, guided by your care team.
• Manage chronic conditions like diabetes that can damage nerves and muscle over time.

Even people with progressive conditions benefit from staying as active as safely possible to preserve strength.

When to See a Doctor

See a doctor if you notice unexplained loss of muscle size or strength, especially in one limb. Seek prompt evaluation if muscle wasting comes with:

• Rapidly worsening or spreading weakness
• Muscle twitching, cramps, or wasting of the tongue or hands
• Trouble swallowing, speaking, or breathing
• Numbness, tingling, or loss of coordination
• Unexplained weight loss or feeling persistently unwell

Difficulty breathing or swallowing is a medical emergency. Progressive, spreading wasting may signal a nerve or muscle disease that benefits from early diagnosis.

Related Topics

Frequently Asked Questions

References

1. National Institute on Aging (NIA). Exercise and physical activity.
2. Mayo Clinic. Muscle weakness and wasting.
3. MedlinePlus, U.S. National Library of Medicine. Muscle atrophy.
4. National Institute of Neurological Disorders and Stroke (NINDS).