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December 2, 2025
Dr. Andrea Gartenbach
Dr. Andrea Gartenbach is a specialist in internal and functional medicine and an expert in longevity. In the second part of her column, she explains why muscles are the most important metabolic organ and how to optimally meet your protein needs.
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Do you know which organ most critically influences our biological age? It's our muscles. Yes, you read that correctly. While a trained body is naturally visually appealing and looks youthful, our muscle tissue is primarily not an aesthetic accessory, but a highly active metabolic organ.
Each of its fibers biochemically communicates with the liver, fat tissue, brain, and immune system. This communication shapes our energy balance day by day, breath by breath, heartbeat by heartbeat. Therefore, it is essential for our healthy energy metabolism and well-being to have enough muscle mass. And at any age, but especially as we get older.
An example from my practice: I remember a patient in her early 50s who suffered from constant exhaustion, sleep problems, concentration difficulties, and lack of libido. The lab values were largely inconspicuous, but the insulin level was slightly elevated despite a balanced diet.
Dr. Andrea Gartenbach, internist and Director of Clinical Education, Geneva College of Longevity Science
The underlying problem: She had massively lost muscle over the years. With menopause, a metabolic chain reaction set in. Her body no longer had reserves to generate energy flexibly. Her meditation and yoga practice and the light running training she had established to compensate for her predominantly sedentary professional activity were not sufficient to counteract the negative effects. Only targeted strength training with sufficient protein intake brought her body back into balance.
Every muscle activity initiates a molecular messaging system in the body. Active muscle fibers release myokines, bioactive signaling substances that work through the bloodstream, reducing inflammatory processes and improving the insulin sensitivity of the cells.
Regular exercise not only strengthens the muscles but also optimizes cellular signaling. Studies show that just two strength training sessions per week can enhance mitochondrial function and significantly improve insulin sensitivity. Both are key factors for metabolic health and the prevention of chronic diseases.
Muscles are therefore not just an active endocrine organ orchestrating metabolism. Exercise is not an optional lifestyle factor, but a molecularly precise instrument that directly intervenes in central metabolic and inflammatory processes and is therapeutically effective.
To maintain and renew muscles, they need sufficient raw materials. Protein provides amino acids, from which enzymes, hormones, and cell structures are formed.
But as so often in biology, the dose determines the direction. Too little protein leads to muscle loss and a slowed metabolism. Too much, on the other hand, keeps the system in a constant state of growth and inhibits cell cleansing (autophagy), which is essential for longevity. We don't want that either, as it can promote aging processes.
The goal is biochemical balance. About 1.2 grams of protein per kilogram of body weight per day are generally considered functionally optimal. The context is crucial here.
This creates a dynamic change between stress and regeneration, a biological basic rhythm that longevity research has identified as a central mechanism for healthy aging. In metabolically active phases, the cell produces energy, synthesizes new cell components, and drives growth. In regenerative phases, on the other hand, it activates repair programs, clears damaged structures, and renews itself from within.
Quality over ideology: The debate on whether animal or plant protein is better often misses the point. It's not about plant-based or animal-based, but the biological value of the protein, meaning its amino acid profile and its usability in the body.
Fish, eggs, fermented dairy products, legumes, and nuts provide different, complementary spectrums of essential amino acids and metabolism-relevant micronutrients. Leucine, methionine, and glycine are particularly relevant as they play central roles in muscle building, regeneration, and detoxification.
Whether animal, plant, or combined - the principle is not what's important, but the individual case: the biological value, the individual metabolic reaction, and personal tolerance. Here too, it's necessary to know your own body: Those who keep an eye on parameters such as body composition (e.g., via BIA), insulin, or IGF-1 quickly understand that individual protein requirements are dynamic and very personal.
Muscular intelligence: Muscles grow not through more, but through targeted stimuli. Short, clearly dosed loads – about three strength training sessions per week of 30 minutes each – trigger stronger adaptation impulses than rare, overly long, or extremely intense training. The key is regularity and the quality of movement execution, not the maximum weight moved.
With each muscle contraction, the activity of the mitochondria, those cell organelles that produce energy, increases. When they are repeatedly challenged, they multiply and optimize themselves. Metabolism works more efficiently, resilience and recovery improve. Studies show that people with well-preserved muscle mass have lower inflammation levels, more stable blood sugar profiles, and higher functional health in old age.
Muscles are thus stored adaptability, a biological protective mechanism against age-related functional loss. And this mechanism remains trainable for a lifetime.
Coherence is crucial here. Those who are active in the morning signal to the body a need for energy and benefit from a nutrient-rich meal. Those who wind down in the evening support recovery by reducing late, digestion-intensive meals. This alignment between activity and food intake stabilizes circadian gene regulation and dampens nighttime stress metabolism, thereby strengthening the synchrony between metabolic and hormonal clocks.
Even small adjustments have measurable effects:
A protein-focused breakfast supports the balance of cortisol and blood sugar.
A targeted post-workout meal with protein and high-quality fats improves recovery and metabolic response.
Breaks of four to five hours between meals allow insulin to drop again, facilitating the metabolic switch to cell repair and fat metabolism.
These seemingly simple decisions collectively change the metabolic signaling landscape. The body returns to a more stable biological rhythm. Energy levels become more consistent, and blood sugar, insulin, and stress signals fluctuate less.
In recent years, the perspective on muscle tissue has radically changed: It is now considered an endocrine organ, a hormone producer actively influencing metabolism and the immune system.
Active muscles release substances that protect the brain, strengthen the immune system, and promote fat burning. People with higher muscle mass have a significantly lower risk of diabetes, depression, and cardiovascular diseases.
The link to longevity is also clear. Studies show that muscle strength and grip strength are better predictors of lifespan than cholesterol or weight. Muscle is the true vitality marker of our time.
Muscles stabilize blood sugar. They actively take up glucose and prevent insulin resistance.
Muscles regulate inflammation. Each contraction releases myokines that reduce systemic inflammation.
Muscles promote hormonal balance. They improve testosterone and estrogen effects and support the adrenal system.
Muscles extend lifespan. Studies show a direct correlation between muscle mass and the probability of survival in old age.
Conclusion
Metabolic health and muscle physiology are among the strongest influences on how well we age. Muscles and protein intake are a key duo in this. Muscles create structure and metabolic activity, proteins provide the building blocks for repair, adaptation, and signaling processes. Both follow the basic principles of physiological adaptation: stimulus, response, regeneration.
The crucial factor is the repeated cycle of stress stimulus and regeneration. This cycle promotes mitochondrial function, stabilizes hormonal regulation, and maintains metabolic flexibility.
Muscle is thus less an aesthetic goal and more an indicator of systemic metabolic health.
Metabolic competence is reflected in the ability to efficiently switch between activity and regeneration, between energy extraction and physiological rebuilding.
In this ability to switch – between building up and regeneration – lies the biological principle of healthy aging.
