Dear readers,
Nobody thinks about their muscle until it’s gone.
That’s the honest truth. Most of my patients come to me focused on fat — how to lose it, where it’s coming from, why it won’t budge. And fat matters, absolutely. But underneath that conversation is one I think is even more important, especially as we age.
Muscle.
Not the bodybuilder kind. Not the aesthetic kind — though that’s a nice bonus. I’m talking about the metabolic, functional, life-giving tissue that determines how well you move, how fast your metabolism runs, how well your blood sugar is controlled, how quickly you recover from illness or injury, and frankly, how long you live well.
Muscle is not vanity. Muscle is medicine.
Let me explain how it works.
What Is Muscle, Really?
Your body has three types of muscle — cardiac muscle (your heart), smooth muscle (your organs), and skeletal muscle— the kind attached to your bones that lets you move, lift, run, and carry groceries.
Skeletal muscle is what we’re talking about today. It makes up roughly 30 to 40 percent of your total body weight — or at least, it should. It is the largest organ system in your body. And it is metabolically extraordinary.
Muscle tissue burns calories even at rest. It stores glucose as glycogen, acting as a buffer against blood sugar spikes. It produces signaling molecules called myokines that communicate with your brain, your fat tissue, your immune system, and your organs — essentially acting as a messaging system that keeps your entire body talking to itself properly.
When muscle is healthy and abundant, your whole biology runs better. When it declines, everything downstream suffers.
Pearl: The single best thing most of my patients can do for their metabolic health — better than any supplement, better than any diet tweak — is build and preserve muscle tissue. Muscle is the organ of longevity. I mean that literally.
How Muscle Is Built: The Story of a Hard Workout
Let’s walk through what actually happens when you build muscle, because most people have the story slightly wrong.
You go to the gym. You lift something heavy. And here’s the part nobody tells you in a way that sticks: the workout itself does not build muscle. The workout damages muscle. Deliberately, productively damages it — but damages it nonetheless.
When you lift a weight that challenges your muscles, you create tiny tears in the muscle fibers. This is called mechanical tension — the physical stress of a load your muscle has to work hard to handle. You also create metabolic stress — the burn you feel when you’re pushing through those last few reps.
Your body senses this damage and immediately mobilizes a repair response. Satellite cells — specialized muscle stem cells that live along the surface of muscle fibers — activate and rush to the site of damage like a construction crew showing up after a storm. They fuse to the existing muscle fibers and donate new material, rebuilding them thicker and stronger than before.
This rebuilding process is called muscle protein synthesis — your body literally manufacturing new protein structures to repair and upgrade the damaged tissue. It takes anywhere from 24 to 72 hours, which is why rest days are not laziness. They are when the actual building happens.
Pearl: The workout is the stimulus. The rest is where the magic occurs. If you’re training hard every day without adequate recovery, you’re repeatedly tearing down without giving your body the time it needs to build back up. More is not always more.
What Muscle Needs to Grow: The Raw Materials
For muscle protein synthesis to happen, your body needs two things working in its favor: the right hormonal environment and enough raw materials — specifically protein.
Protein: The Building Blocks
Muscle is made of protein. And protein is made of amino acids — small molecular units that link together like LEGO pieces to form muscle fibers. There are 20 amino acids your body uses, and 9 of them are essential, meaning your body can’t make them — you have to eat them.
Leucine is the most important one for muscle building. It acts like a key that turns on the muscle-building machinery — specifically a pathway called mTOR (mechanistic target of rapamycin), which is essentially the master switch for muscle protein synthesis. When leucine shows up after a workout, mTOR activates and the building process begins.
This is why protein quality matters — not just quantity. Animal proteins (meat, eggs, fish, dairy) are rich in leucine and contain all essential amino acids in the right proportions. Plant proteins often don’t — which doesn’t mean a plant-based diet can’t support muscle building, but it means you have to be more intentional about combining sources and hitting adequate totals.
Pearl: Most of my patients are significantly under-eating protein — especially women. The old recommendation of 0.8 grams per kilogram of body weight is the minimum to avoid deficiency, not the amount needed to build and preserve muscle. For active people and anyone over 40, I typically aim for closer to 1 gram per pound of body weight. That number surprises people. It shouldn’t.
Hormones: The Foreman on the Construction Site
Protein provides the raw materials. Hormones are the foreman telling the crew what to do with them.
Testosterone is the most well-known anabolic — meaning muscle-building — hormone. It directly stimulates muscle protein synthesis, increases the sensitivity of muscle cells to growth signals, and supports recovery. This is true for both men and women. Women have lower levels of testosterone than men, but those lower levels are still critically important for maintaining muscle mass, strength, and metabolic function. When testosterone declines — as it does with age, stress, poor sleep, and hormonal imbalance — muscle building becomes significantly harder.
Growth hormone and its downstream mediator IGF-1 (insulin-like growth factor 1) are powerful drivers of muscle repair and growth. Growth hormone is released primarily during deep sleep — which is one of the most important and underappreciated reasons that poor sleep destroys body composition. You literally cannot build muscle optimally without adequate deep sleep.
Insulin — yes, the same hormone we talked about in fat storage — plays an important role in muscle building too. It is anabolic in the right context, shuttling amino acids into muscle cells after a meal. This is why eating protein around your workouts matters, and why extreme low-calorie or zero-carb approaches can sometimes undermine muscle building even when protein intake is adequate.
Cortisol — the stress hormone — is catabolic, meaning it breaks muscle down. Chronic stress is literally eating your muscle. I see this in patients who train hard, eat well, and still can’t build or maintain muscle — and their cortisol is through the roof.
Pearl: You can do everything right in the gym and at the dinner table and still lose muscle if your hormonal environment is working against you. This is why I don’t just hand patients a workout plan. I look at the full hormonal picture. Testosterone, growth hormone, cortisol, thyroid — all of it. The biology has to support the effort.
Muscle Breakdown: When the Body Eats Itself
Now for the other side of the equation — and the side that matters more than most people realize.
Your body is constantly breaking muscle down and rebuilding it. This is normal. It’s called protein turnover, and it’s happening right now, in every one of your muscles, whether you’re working out or not. The question is which direction the balance tips — are you building more than you’re breaking down, or breaking down more than you’re building?
When breakdown exceeds building, the result over time is sarcopenia — the gradual loss of muscle mass that begins in your 30s and accelerates significantly after 40 if you’re not actively working against it. After age 40, the average person loses 3 to 5 percent of their muscle mass per decade without intervention. By the time most people notice it — when they feel weak, when their metabolism slows, when they start falling — they’ve already lost significant ground.
Several things accelerate muscle breakdown:
Not eating enough protein. When your body is low on amino acids and needs to keep vital organs running, it will cannibalize muscle tissue to get them. Your body will sacrifice your biceps to keep your heart beating. Every time.
Not moving. Muscle follows the principle of use it or lose it with ruthless efficiency. Even a few weeks of immobility — after surgery, illness, or just a sedentary stretch — can result in significant muscle loss. The body doesn’t maintain tissue it doesn’t need.
Chronic stress and elevated cortisol. Cortisol breaks down muscle protein for fuel. A chronically stressed body is a chronically catabolic body.
Poor sleep. Growth hormone — your primary muscle repair signal — is released during deep sleep. Shortchange your sleep and you shortchange your recovery and your muscle.
Declining hormones. The drop in testosterone and growth hormone that comes with aging is one of the primary biological drivers of sarcopenia. This is not inevitable — it’s addressable — but it requires attention.
Undereating overall. Aggressive caloric restriction, especially without adequate protein, is one of the fastest ways to lose muscle. Many people who lose weight quickly through severe restriction are losing as much muscle as fat — which is a metabolic disaster. The scale goes down, but the metabolism slows, and keeping the weight off becomes harder than ever.
Pearl: Crash diets don’t just fail — they often leave you worse off than when you started. Less muscle means a slower metabolism, which means the same amount of food that once maintained your weight now causes gain. This is the cycle I work hard to help patients break.
Peptides and Muscle: The Next Level
For patients who want to take muscle preservation and building seriously — particularly those dealing with age-related decline, recovery challenges, or significant hormonal shifts — peptides are a powerful tool.
Ipamorelin and CJC-1295 are growth hormone secretagogues — they stimulate your own pituitary gland to produce more growth hormone naturally. The result is improved muscle repair, better recovery, enhanced body composition, and deeper sleep. For patients in their 40s and beyond who are noticing the subtle signs of GH decline, these can make a significant difference.
BPC-157 is remarkable for musculoskeletal repair — tendons, ligaments, muscle tears. It accelerates healing through multiple pathways and can be genuinely life-changing for patients dealing with injuries that just won’t resolve.
MK-677 is another growth hormone secretagogue that supports muscle mass and recovery, particularly useful for patients who need to rebuild after illness, surgery, or a period of significant physical decline.
These aren’t shortcuts. They’re targeted biological tools that work with your body’s own repair systems — making the effort you’re already putting in work better and more efficiently.
The Simple Version
Here it is, as simply as I can say it:
Muscle is built when your body repairs damage from exercise using protein as raw material, driven by hormones like testosterone and growth hormone — primarily during rest and sleep. Muscle is broken down by inactivity, undereating, poor sleep, chronic stress, and hormonal decline. The balance between building and breakdown determines your body composition, your metabolism, your health, and your longevity.
The levers you control: lift weights, eat enough protein, sleep deeply, manage stress, and address your hormones.
That’s it. The biology is complicated. The actions are not.
Why This Matters More Than You Think
I want to close with this, because I think it reframes everything:
Muscle mass is one of the strongest predictors of longevity and health span we have. People with more muscle live longer, recover faster from illness, have better insulin sensitivity, lower rates of cardiovascular disease, better cognitive function, and significantly lower rates of disability as they age.
This is not about looking a certain way. This is about building the biological infrastructure that lets you live fully — for as long as possible.
Your muscle is worth fighting for. Let’s make sure you keep it.
Your Next Step
If you’ve been reading this and thinking, “I need to see what my body is doing.”
This is your sign. The sooner you understand your metabolic patterns, the sooner you can start making progress again.
To get started:
Call our office at 703-666-4144 or schedule a consultation with us.
Dr. Aleksandra Gajer
Founder, The Gajer Practice | Burke, Virginia
Board-Certified Physician | Functional & Performance Medicine
