Understanding What is it called when your body eats muscle? (Nutrition & Diet)

October 28, 2025 •

4 min read

During extreme starvation or inadequate nutrition, the body resorts to breaking down its own muscle tissue for fuel. Understanding what is it called when your body eats muscle? is the first step toward preventing this damaging process and protecting your lean mass through proper nutrition and diet.

Quick Summary

The body breaks down muscle through metabolic processes like catabolism and proteolysis, leading to atrophy. This is caused by factors including malnutrition, illness, inactivity, and excessive exercise.

Key Points

Catabolism: The process of your body breaking down its own muscle for energy is called catabolism.
Muscle Atrophy: The resulting loss of muscle mass from catabolism and other factors is known as muscle atrophy.
Protein is Key: Consuming adequate protein is essential for preventing muscle breakdown and promoting muscle growth.
Exercise Matters: Regular resistance training signals to the body that muscle mass is necessary and promotes protein synthesis.
Balance is Crucial: Maintaining a proper balance between caloric intake, protein consumption, and physical activity is vital for preserving lean muscle.

The Science Behind Muscle Breakdown: Catabolism

When your body consumes its own muscle tissue for energy, it's a process of cellular breakdown known as catabolism. This is the opposing force to anabolism, which is the process of building and repairing tissues. In a healthy state, the body maintains a balance between these two processes, known as metabolic balance. However, under certain conditions, the catabolic rate can surpass the anabolic rate, resulting in a net loss of muscle mass.

This is not a single event but a complex metabolic shift. The body's priority is to maintain energy for vital organs, especially the brain, which relies heavily on glucose. When carbohydrate stores (glycogen) are depleted, the body begins converting other fuel sources, including amino acids from muscle protein, into glucose through a process called gluconeogenesis. This metabolic adaptation is a survival mechanism, but it comes at the expense of lean muscle tissue.

What are the Primary Terms for Muscle Loss?

Several terms are used to describe the phenomenon of muscle loss, each with a slightly different meaning:

Catabolism: The general metabolic process of breaking down complex molecules for energy. Muscle protein breakdown is a catabolic process.
Muscle Protein Breakdown (MPB): The specific biochemical process of dismantling muscle proteins into amino acids. This is constantly happening but accelerates during periods of insufficient nutrition or stress.
Muscle Atrophy: This is the result of prolonged catabolism—the wasting or thinning of muscle mass. Atrophy can be caused by disuse, malnutrition, or disease.
Sarcopenia: A specific type of muscle atrophy that is age-related. It is the gradual and progressive loss of muscle mass and strength that occurs with aging.
Cachexia: A severe, involuntary wasting syndrome involving both muscle and fat loss. It is often associated with chronic diseases like cancer, HIV, or heart failure and can be resistant to nutritional therapy alone.

Key Factors Contributing to Muscle Wasting

Multiple factors can trigger or accelerate muscle breakdown:

Inadequate Nutrition: A calorie deficit, especially a low-protein diet, is a primary driver of muscle catabolism. Without sufficient energy from food, the body turns to its own protein stores for fuel.
Intense Exercise Without Recovery: Overtraining without providing adequate time or nutrients for repair can put the body in a prolonged catabolic state. The exercise itself creates micro-damage to muscle fibers, and without proper protein and carbs, repair is compromised.
Immobilization or Inactivity: If muscles aren't used, the body conserves energy by breaking them down. This type of atrophy is common after injuries requiring bed rest or in individuals with a sedentary lifestyle.
Illness and Chronic Disease: Conditions like cancer, kidney disease, and HIV often involve high levels of inflammation and hormonal changes that promote muscle wasting, as seen in cachexia.
High Stress (Cortisol): The stress hormone cortisol is catabolic, meaning elevated levels can signal the body to break down muscle tissue. Prolonged physical or emotional stress can lead to increased cortisol production.

How to Prevent and Reverse Muscle Loss

Protecting your muscles requires a strategic approach to diet and lifestyle. The goal is to maintain a state of anabolism where protein synthesis outpaces breakdown.

Prioritize Protein: Consuming enough high-quality protein is crucial. Aim for 20-35 grams of protein per meal to maximize muscle protein synthesis. Excellent sources include lean meats, fish, eggs, dairy, and plant-based options like lentils and soy.
Ensure Adequate Calories: Avoid extreme calorie deficits, which force the body into catabolism. A moderate, sustainable deficit is better for fat loss while preserving lean mass.
Incorporate Resistance Training: Strength training provides the stimulus needed to build and preserve muscle. This signals to your body that the muscle is essential, countering the catabolic signals. This includes using weights, resistance bands, or bodyweight exercises.
Rest and Recover: Allow adequate rest between workouts for muscle repair. Sleep is a critical anabolic period where growth hormone is released, aiding recovery.
Stay Hydrated: Dehydration can impair muscle function and accelerate catabolism, so drinking plenty of fluids is important.
Support with Nutrients: Certain micronutrients support muscle health, including Vitamin D, Omega-3 fatty acids, and Creatine.

Catabolism vs. Anabolism: A Comparison


Feature	Catabolism	Anabolism
Primary Function	Breaks down complex molecules for energy.	Builds new, complex molecules and tissues.
Energy Requirement	Releases energy from broken chemical bonds.	Requires energy input to create new bonds.
Hormones Involved	Cortisol, Glucagon, Adrenaline.	Insulin, Growth Hormone, Testosterone.
Effect on Muscle Mass	Decreases muscle mass (muscle atrophy).	Increases muscle mass (muscle hypertrophy).
Typical Triggers	Fasting, intense exercise, illness, stress.	Feeding, rest, resistance training.
Role in Metabolism	Part of the body's survival mechanism for fuel.	Critical for growth, repair, and adaptation.

Conclusion

When your body "eats muscle," it is undergoing a catabolic process, often leading to muscle atrophy or wasting. While a natural part of metabolism, excessive muscle breakdown can be a sign of poor nutrition, overtraining, or underlying health issues. Fortunately, this process can be managed through a balanced diet rich in protein, a consistent exercise routine incorporating resistance training, and adequate rest. By understanding the metabolic battle between catabolism and anabolism, you can take proactive steps to protect and build your muscle mass, regardless of your age or activity level.

For more information on the mechanisms of muscle atrophy, consult resources from authoritative health organizations like the Cleveland Clinic.

Frequently Asked Questions

Catabolism is the metabolic process of breaking down molecules for energy, while anabolism is the process of building and repairing tissues, such as muscle. The balance between these two processes determines if you gain or lose muscle mass.

Muscle protein breakdown is a continuous process as part of normal protein turnover. However, the rate of breakdown can increase significantly due to factors like fasting, intense exercise, or inadequate protein intake.

Muscle loss is a risk during dieting, especially with extreme calorie deficits. However, it can be minimized or prevented by consuming enough protein and incorporating regular resistance training to preserve lean mass.

Resistance training creates tension on muscle fibers, which stimulates muscle protein synthesis and signals to your body that the muscle is needed. This helps offset muscle protein breakdown and promotes growth, even during a calorie deficit.

Sarcopenia is a specific type of muscle atrophy that occurs naturally with aging. It leads to a progressive loss of muscle mass and strength, but its effects can be mitigated with exercise and proper nutrition.

Chronic illnesses can cause muscle wasting through a syndrome called cachexia. This is driven by inflammation and hormonal changes that increase the rate of muscle and fat breakdown, even with adequate calorie intake.

Cortisol is a stress hormone that promotes muscle catabolism. High or prolonged levels of cortisol, often triggered by stress, sleep deprivation, or overtraining, can increase muscle breakdown and hinder muscle growth.