Anabolic Resistance: Why Muscle Gains Change With Age

TL;DR

What is “anabolic resistance” in plain English?

When you’re younger, your muscles are like a microphone turned up to 10. You eat protein, you train, and they “hear” that signal and build new tissue.

With age, that same microphone gets turned down. The Nutrients review describes age-related anabolic resistance as a reduced ability of older muscle to respond to anabolic stimuli such as exercise and protein intake ¹. In other words, the signal is the same, but the response is smaller.

In one of the summary diagrams, the authors show three key ideas:

• Protein alone: Older adults get a smaller spike in muscle-protein synthesis (MPS) than younger adults from the same dose.
• Exercise alone: A workout still stimulates MPS, but the increase is blunted with age.
• Protein + exercise together: The combination is still powerful, and still your best tool, but older muscle doesn’t get quite the same boost as young muscle ¹.

That’s the core of anabolic resistance: the “build muscle” signal still works, but you may need to send it louder and more consistently as you age.

Why this matters even if you train hard

The review also looks at master athletes — people in their 50s, 60s, or older who have trained and competed for years. They tend to be leaner, fitter, and have better blood-sugar control and less sarcopenic obesity than inactive adults their age ¹.

But when researchers dig into the muscle level, the picture gets more nuanced:

• In one study, older endurance athletes completed a brutal 3-day downhill running protocol. Over the next 72 hours, their muscle-building response was lower than that of younger athletes who did the exact same work — even with solid protein intake ¹.
• In another experiment, older master endurance athletes had a muscle-protein response to a resistance-training session that was similar to untrained older adults, not clearly better, despite years of training history ¹.

So long-term training is hugely beneficial for health and performance, but it does not completely erase the age-related drop in muscle responsiveness. Even “high performers” still have to respect the biology.

The big drivers you can actually influence

Some aspects of anabolic resistance come with age itself — changes in digestion, blood flow, hormones, and cellular signaling. But the review highlights several modifiable factors that often travel with aging and make things worse ¹:

• More sitting, less daily movement. Step-reduction studies show that when older adults suddenly cut back their daily steps, they rapidly lose leg muscle and their response to a high-protein meal shrinks.
• Insulin resistance and higher blood sugar. When the muscle is less sensitive to insulin, it has a harder time taking up amino acids and using them to build tissue.
• Extra body fat, especially around the waist. Higher fat mass is tied to inflammation and metabolic stress, which can further dampen muscle’s anabolic response.
• Chronic, low-grade inflammation. Pro-inflammatory cytokines and oxidative stress interfere with the signaling pathways that turn protein and training into new muscle proteins.

You cannot change your birth year. You can change how much you move, how you eat, and how often your muscles get a clear, strong “use me” signal.

How much protein do you really need after 40?

The standard RDA of 0.8 g/kg/day was never designed for athletes or for preserving performance into older age. Multiple expert groups now recommend higher intakes for older adults, especially if they train ^{2, 3, 4}:

• General older adults (65+): often 1.0–1.2 g/kg/day is recommended to help maintain muscle and function, even without heavy training ^{2, 3}.
• Older adults with illness, injury, or high stress: needs may rise to 1.2–1.5 g/kg/day during recovery under professional guidance ².
• Active adults & master athletes: position stands for exercising individuals typically recommend around 1.4–2.0+ g/kg/day, with many older lifters and endurance athletes landing in the 1.6–2.0 g/kg/day range when trying to build or strongly protect muscle ^{3, 4}.

For a 170-lb (77-kg) master athlete, that’s roughly:

• General health (1.2 g/kg): about 90–95 g/day.
• Performance focus (1.6–2.0 g/kg): about 125–155 g/day.

Equally important is per-meal dose. Because of anabolic resistance, older adults usually need a bigger protein pulse per meal to trigger the same response seen in younger people. The review and supportive guidelines converge around 0.3–0.5 g/kg per meal — roughly 25–40 g of high-quality protein for most adults ^{1, 3}.

Quality matters: leucine and high-quality protein

Not all protein hits your muscles the same way. One of the key amino acids in this story is leucine. Leucine acts like a trigger for mTOR, one of the main pathways that flips on muscle-protein synthesis after eating or training.

The review notes that older adults often benefit from leucine-rich protein sources, or small additions of leucine/essential amino acids to a meal, to get over the “threshold” needed to fully activate MPS ¹. In practice, that usually means:

• Dairy proteins: whey, Greek yogurt, cottage cheese.
• Animal proteins: eggs, poultry, beef, fish.
• Leucine-conscious plant combos: soy, plus mixes of legumes and grains (like beans + rice) for those who prefer plant-based patterns.

For many over-40 lifters and runners, simply front-loading breakfast with 25–35 g of protein (instead of a low-protein, high-carb start) is a game-changer for daily muscle protection.

Smart supports: HMB and omega-3 fats

Two supplemental tools discussed in the review and related research are:

HMB (β-hydroxy β-methylbutyrate)

• HMB is a metabolite of leucine that has been studied in older adults and in models of bed rest or high stress.
• Trials suggest HMB can help limit muscle loss and support strength when people are immobilized or in catabolic states, especially when combined with adequate protein and training where possible ¹.

Omega-3 fatty acids (EPA and DHA)

• Omega-3 fats from fish oil appear to enhance some aspects of muscle anabolic signaling and may increase the rate of muscle-protein synthesis in older adults in certain settings ⁵.
• A recent meta-analysis points to mixed but promising results overall, and omega-3s also support heart and brain health, making them a reasonable part of a broader longevity strategy for many people ⁶.

These are not magic. They’re potential add-ons to a solid base of resistance training, daily movement, and consistent protein — not substitutes.

Avoid the “always dieting” trap

Many master athletes, tactical professionals, and type-A high performers try to stay “lean” year-round with long-term calorie restriction. The problem: chronically low energy availability can worsen anabolic resistance.

The review warns that extended periods of energy restriction, even with decent protein intake, can blunt MPS and accelerate muscle loss, especially in older adults ¹. Signs you may be in this trap include:

• Persistent fatigue or heavy legs in training.
• Stagnant or declining strength despite hard work.
• Sleep disruption, irritability, or frequent minor illnesses.

Short, strategic “cut” phases can be fine. Living in an endless diet is not. Your muscles need both building blocks (protein) and energy to respond to training.

Putting it together: a simple master-athlete day

Here is a simple high-level example for a 170-lb (77-kg) adult aiming for ~140 g of protein (about 1.8 g/kg/day). This is not a prescription, just a starting template to adjust with your coach or clinician.

• Breakfast (post-walk): 3 scrambled eggs + a cup of Greek yogurt with berries and a small handful of nuts (~35–40 g protein).
• Lunch: Big salad with 5–6 oz grilled chicken or tofu, olive oil dressing, and a side of quinoa or beans (~30–35 g protein).
• Afternoon training: Strength session (squats, hinges, pushes, pulls, carries) 2–3x/week, with easy cardio or intervals on other days.
• Post-workout / snack: Protein shake or smoothie with fruit and ~25–30 g protein.
• Dinner: 5–6 oz salmon, potatoes or rice, and roasted vegetables (~35–40 g protein) plus a source of omega-3s if needed.

If you use a coaching app or platform, this is exactly where we’d align training days, protein timing, and recovery days so your muscles keep “hearing” the message to stay strong as you age.

Who should talk with a clinician first?

This article is for general education. It is not medical advice or a diagnosis. Before making big changes to your diet or supplement routine, talk with your clinician if you:

• Have kidney, liver, or significant heart disease.
• Take medications that interact with protein, omega-3s, or other supplements.
• Are recovering from surgery, cancer treatment, or a major injury.
• Are pregnant, nursing, or managing complex endocrine or autoimmune conditions.

For many healthy adults, especially those already training, the bigger risks are too little protein, too much sitting, and too much chronic dieting — but it’s still wise to individualize your plan.

Want to go deeper? You can read the full clinical review and key position papers below.