You've heard the advice enough times to stop counting. Trainers, health articles, the friend who started lifting at 45 — everyone says the same thing: eat more protein as you get older. They're right. The direction has been correct for years.
What none of them explained is why the old amount stopped being enough. Not because your muscles weakened. Because somewhere around your forties, your muscles quietly turned down the volume on every gram you eat. The signal you send with a post-workout meal at 25 arrives dimmer at 48. Same food. Same muscles. A smaller response behind the scenes.
How Much More Protein Do You Need as You Get Older?
The mechanism is called anabolic resistance, and it's less dramatic than it sounds. Each gram of protein you eat now triggers 40% less muscle-building activity than the same gram triggered twenty years ago. Not because the protein changed — because the cellular machinery reading the signal became less responsive over time. Your muscles haven't weakened. They've become harder to reach.
The gap is wider than most protein conversations suggest. Younger adults max out their muscle-building response at about 0.25 grams of protein per kilogram of body weight per meal. Past 65, that threshold climbs to roughly 0.40 — a 60% higher per-meal dose to produce the same peak output. For someone weighing 75 kilograms (165 lbs), that's the difference between needing 19 grams at a meal and needing 30. The portion you've been eating post-workout since your twenties may have quietly slipped below the line.
UNDER 40
~0.25 g protein per kg per meal to max out muscle building
OVER 65
~0.40 g protein per kg per meal to reach the same peak — 60% more
Across a full day, the math scales. Three meals at the higher threshold puts the daily target around 1.2 grams per kilogram — 50% above the standard recommended daily allowance of 0.8 that most nutrition labels reference. The RDA was built from studies in young adults. It was never designed for a body running on less-sensitive machinery — and the gap becomes even more critical when you're cutting calories.
Older adults need roughly 60% more protein per meal to maximally stimulate muscle building — about 0.40 g/kg compared to 0.25 g/kg for younger adults. Spreading intake across three meals at the higher threshold puts the daily target near 1.2 g/kg, which is 50% above the standard recommended allowance. Resistance training combined with adequate protein can largely close the remaining gap.
— Moore et al. 2015 · J Gerontol A Biol Sci Med Sci · n=108 | Kristiansen et al. 2026 · Front Physiol · n=1,280
None of which means the machinery is broken. When older muscles get enough protein — when they clear that higher per-meal threshold — the peak building rate is virtually identical to a 22-year-old's. The ceiling didn't drop. The floor to reach it rose. Your muscles at 60 can still build at the same speed they always could. They just need a louder signal to start.
And protein isn't the only lever. A 2026 meta-analysis of age-related anabolic resistance found that resistance training largely eliminates the gap. In the majority of studies measuring post-exercise muscle building, older and younger adults showed no meaningful difference. The pattern held even more strongly when protein and exercise were combined. Anabolic resistance, the researchers concluded, appears "mostly when the combined stimuli is weak."
Most of this evidence comes from measuring muscle protein synthesis over hours — not tracking actual muscle gains over months or years. The per-meal threshold tells you where the building response peaks in a lab window. It doesn't guarantee that eating above it automatically translates to more muscle on your frame. The direction of evidence is strong and consistent. The long-term picture is still filling in.
Your muscles haven't lost their capacity. They've raised their admission price — and the receipt now includes both a per-meal protein dose and a training stimulus. One without the other leaves the gap open.
The full per-meal data behind these numbers goes deeper than one threshold. The training side — how much volume, what kind of loading, whether the equation changes after 40 — is its own evidence story. It does.