The quiet tax of anabolic resistance after 40

The standard advice on protein for women over 40 is a quiet disaster of outdated numbers. If you're aiming for the old 0.8 grams per kilogram of bodyweight, you are systematically underfunding your own physiology. The real target is 1.2 to 1.5 grams per kilogram, daily. But this isn't about hitting a macro target to feel virtuous. It's about providing the raw materials for a system under constant renovation, a system that treats muscle as its most valuable, and expensive, metabolic currency.

You eat 'healthy'. A salad for lunch, some yoghurt, maybe a handful of nuts. You go for walks, you do the occasional yoga class. Yet you feel a creeping sense of fragility. Workouts that used to feel invigorating now just leave you drained for two days. You drop things more often. That stubborn jar of olives requires a tactical intervention. You chalk it up to 'just getting older', a story the world is all too happy to tell you. It is not a story; it is a resource deficit. Your body is quietly liquidating its most expensive assets—your muscle—to pay for the day's energy budget, and nobody sent you the invoice.

Muscle is a metabolic savings account, not just scaffolding

You've been taught to think of muscle as the machinery for movement. This is true, but it's a dangerously incomplete picture. Your skeletal muscle is your primary metabolic sink. It is the largest site for glucose disposal in your body after a meal, a crucial buffer against insulin resistance. When you have adequate muscle mass, it's like having a high-capacity pantry for incoming energy; there's always a place to put the groceries. When you lose muscle, that pantry shrinks. Glucose has nowhere to go, so it hangs around in the bloodstream, contributing to energy crashes, brain fog, and the slow, steady creep of metabolic dysfunction.

This isn't just about blood sugar. Muscle is also an endocrine organ, secreting signalling molecules called myokines in response to contraction. These molecules talk to your fat tissue, your liver, your brain, and your immune cells. They are profoundly anti-inflammatory. Losing muscle means turning down the volume on this vital communication channel. Your body becomes a noisier, more inflammatory place. The fatigue, aches, and low-grade malaise you associate with aging are often the direct result of this metabolic and signalling deficit. Adequate protein is the non-negotiable budget line item to keep this account from being overdrawn.

Anabolic resistance: Your muscles are getting hard of hearing

As you get older, your muscle tissue develops what's known as 'anabolic resistance'. It's not that your muscles forget how to build and repair themselves; it's that they become less sensitive to the signal. The same meal that would have easily triggered muscle protein synthesis (the process of building new muscle) in your twenties barely gets a response in your fifties. The signal is the same, but the receiver's volume is turned down.

This is where the dose and quality of protein become critical. To overcome this resistance, you need a larger stimulus. Specifically, you need a sufficient dose of the amino acid leucine in a single meal—around 2.5-3 grams—to act as the ignition key for muscle protein synthesis. Spreading your protein thinly across the day in small snacks and undersized portions is like politely tapping on the door when you need to ring the bell. You're not giving the system a clear enough signal to begin the expensive work of repair and construction. This is why the advice shifts from just total daily protein to ensuring you have at least one or two meals with a solid 30-40 gram bolus of high-quality protein. It's not about eating more, necessarily. It's about speaking a language your muscles can still hear.

Common Questions

How much protein do I actually need after 40?

Aim for 1.2 to 1.5 grams of protein per kilogram of your ideal bodyweight, daily. If you are actively training or recovering from illness, aim for the higher end of that range, up to 2.0g/kg. Distribute this across 3-4 meals for best results.

Does eating more protein harm your kidneys?

This is a persistent myth based on outdated observations in people with pre-existing, severe kidney disease. For individuals with healthy kidneys, a high protein intake is not only safe but necessary for preserving metabolic health and muscle mass with age.

Can I get enough protein on a vegan or vegetarian diet?

Yes, but it requires more planning. Plant proteins are often less dense and may lack a complete profile of essential amino acids in a single source. You must be diligent about combining sources (e.g., grains and legumes) and may need to eat larger volumes to hit your targets.

Closing

Knowing the numbers is one thing. Putting them into practice without turning your life into a spreadsheet is the real work. If you're ready to stop guessing and start building a more resilient system, here are the next steps.

• For a full system diagnostic: The Kokorology Audit is a one-on-one deep dive into your body's unique signalling, capacity, and load.
• For a guided practice: Join the Tired but Wired workshop to learn the tools for regulating a nervous system stuck in overdrive.
• For free weekly insights: Get the Kokorology newsletter for practical, no-hype nervous system education delivered to your inbox.

TL;DR

The conversation about protein intake for women aging needs a serious update. You likely need far more than you think—1.2 to 1.5 grams per kilogram of bodyweight daily—to fight age-related muscle loss. This isn't vanity; muscle is a critical metabolic organ that regulates blood sugar and inflammation. As you age, your body becomes resistant to the signals to build muscle, requiring larger protein doses, especially leucine, to get the job done. Hitting this target is a non-negotiable for preserving your metabolic health and physical capacity.

Sources

• Bauer J et al., for the PROT-AGE Study Group (2013). Evidence-Based Recommendations for Optimal Dietary Protein Intake in Older People: A Position Paper. Journal of the American Medical Directors Association, 14(8), 542–559.
• Morton RW et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. British Journal of Sports Medicine, 52(6), 376–384.
• Prado CM et al. (2025). Muscle Mass Loss With GLP-1 Therapy: Clinical Relevance and Mitigation. Lancet Diabetes & Endocrinology.
• Examine.com (2026). Leucine alone won't save muscle during immobilization. Examine.com Study Summaries — June 8–15, 2026.