Muscle After 40: Why You’re Losing It and How to Get It Back
Sarcopenia is the age-related loss of muscle mass and strength. Starting in your 30s, your body slowly begins to lose muscle tissue—roughly 1% per year—and the process accelerates after 40.
Let’s get something straight. If you're over 40 and struggling to keep your muscle, it's not because you're lazy—or "just getting older." It's because biology is working against you. The process even has a name: sarcopenia.
But here's the good news: you can reverse it. You just have to stop following outdated fitness advice and start training—and fueling—your body based on what the science says about aging, hormones, and muscle physiology.
Let’s break it down.
What Is Sarcopenia—and Why It Starts Around 40
Sarcopenia is the age-related loss of muscle mass and strength. Starting in your 30s, your body slowly begins to lose muscle tissue—roughly 1% per year—and the process accelerates after 40.
But it’s not just about muscle mass. It’s about function. As sarcopenia progresses, men experience:
Reduced strength
Slower metabolism
Poor balance and coordination
More joint pain
Lower testosterone
And yes—higher risk of injury and falls
And here’s the kicker: most men don’t even notice it happening until the effects show up as belly fat, brain fog, or fatigue.
Why You’re Losing Muscle—Even if You Still Work Out
You might still be hitting the gym. So why is your muscle fading?
Let’s talk about the hidden culprits:
1. Low Testosterone
Testosterone is a major anabolic hormone. After 40, levels naturally decline, and when they dip below optimal, muscle protein synthesis slows down.
Translation: You’re breaking down more muscle than you’re building—especially if you’re not managing stress, sleep, or nutrition.
2. Insulin Resistance
As men age, insulin sensitivity declines. When that happens, your body becomes worse at transporting nutrients—like amino acids—into your muscles. So even if you’re eating well, you’re not absorbing efficiently.
3. Chronic Inflammation
Years of stress, poor sleep, gut issues, or overtraining can raise your baseline inflammation. And that directly interferes with muscle recovery and growth hormone production.
4. Outdated Workouts
Doing the same “chest and tris” split you did in your 20s? Not going to cut it anymore.
At 45, you need smarter training, not harder training. That means:
Less volume, more intention
Higher quality reps
Prioritizing recovery just as much as intensity
The 5-Step Plan to Build Muscle After 40
This isn’t about bodybuilding. It’s about keeping the muscle that keeps you strong, sharp, and resilient.
1. Lift Heavy (But Smart)
Use compound movements (think squats, deadlifts, rows) with controlled tempo and lower reps (5–8 range). Rest longer between sets to allow full recovery.
Why it works:
Heavy, low-rep training triggers mechanical tension, which is the strongest driver of muscle growth in men over 40.
Pro tip: Ditch the “pump” workouts. Prioritize strength, not sweat.
2. Prioritize Protein—and When You Eat It
Most men don’t eat enough protein. Or they eat it all at dinner.
Aim for:
1 gram of protein per pound of ideal body weight per day
Spread across 3–4 meals for optimal absorption
Include leucine-rich sources (like eggs, beef, whey)
Why it works: Even with resistance training, older men are less responsive to dietary protein—a concept called anabolic resistance. You need more protein to trigger the same muscle-building signal.
3. Optimize Testosterone and Metabolic Health
If your T is low, your muscle-building potential is too.
What helps:
Strength training (see above)
Sleep (7–8 hours, deep and uninterrupted)
Stress management (cortisol kills gains)
Blood sugar control (ditch the processed carbs)
Testosterone therapy, when clinically indicated
Don’t guess. Run labs. Know your numbers.
4. Stop Ignoring Recovery
Your 20-year-old self could lift hard six days a week and bounce back. At 45? That same routine will drain your nervous system, spike cortisol, and sabotage your muscle gains.
What to do:
Lift 3–4x/week, max
Walk daily for blood flow and insulin sensitivity
Stretch, sauna, or do mobility work 1–2x/week
Sleep like it’s your job
Recovery isn’t optional. It’s the multiplier.
5. Track Progress—Not Just Weight
Muscle is denser than fat. So if you’re gaining strength but the scale isn’t moving, that’s not a plateau—it’s progress.
Track:
Strength numbers (reps, load, performance)
Waist measurements
Energy, mood, libido
DEXA or body comp scans, if possible
Muscle after 40 is less about size, more about function.
Final Word
Most men accept muscle loss as a given. They chalk it up to “getting older.” But the truth is: aging doesn’t have to mean decline.
You can stay strong, fit, and resilient well into your 50s, 60s, and beyond—but only if you stop following cookie-cutter fitness plans and start training in alignment with your biology.
CODEX
The Art of Aging Well
A revolutionary approach, created by award-winning, board-certified physician and surgeon, Dr. Peter Marta, combining the precision of conventional medicine and the nuance of functional medicine. At the heart of Codex is hormone optimization, with a comprehensive system addressing seven core areas vital for men’s wellness. What even many physicians overlook is that hormonal health and gut health are inextricably linked—you can’t have one without the other. Codex addresses these connections, unlocking vitality and balance through a tailored, easy-to-follow, scientific approach.
