Longevity & Aging · Metabolic & Cardiometabolic
dietary protein for muscle plateaus-at approximately 1.6 g/kg/day with no added hypertrophy beyond
In plain terms: Is there a point where extra protein stops building more muscle, around 1.6 g/kg?
Supported as the best current estimate — the pooled breakpoint sits near 1.6 g/kg with wide uncertainty and no demonstrated benefit at 2.2 g/kg, though Topol is right that the underlying meta-regression was not statistically significant, so the exact number is soft.
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: All trials, pooled (Meta-analysis)
How the studies fall
The evidence (12)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Vieira 2022 · Sports Med | meta-analysis | mixed | moderate | Umbrella review found protein supplementation with resistance training yields small, inconsistent added gains in older adults, supporting that benefit plateaus once protein is adequate. |
| Unterberger 2022 · Clin Nutr | RCT | mixed | moderate | RCT doubling protein to ~2 g/kg/day before resistance training in older adults showed it did not clearly outperform normal intake for most outcomes, supporting a plateau but in an older population. |
| Eglseer 2026 · BMC Nutr | RCT | mixed | moderate | Secondary analysis of 3 RCTs in older adults during weight loss found higher protein preserved lean tissue but no benefit for strength/function, a context-dependent caveat to a hard universal plateau. |
| Antonio 2018 · J Funct Morphol Kinesiol | RCT | supports | moderate | One-year RCT in trained women consuming >2.2 g/kg/day found no additional favorable body-composition change vs habitual intake, consistent with no extra benefit far above ~1.6 g/kg. |
| Kirwan 2022 · Am J Clin Nutr | meta-analysis | mixed | moderate | In older adults protein augments RET-induced appendicular lean mass/grip modestly and inconsistently — no evidence of dose-dependent benefit into the 2+ g/kg range, consistent with a plateau. |
| Ely 2025 · Nutrients | RCT | mixed | moderate | Acute RCT in young men showed leucine-rich lower-dose protein stimulated muscle protein synthesis comparably to larger doses, supporting a saturable/plateau MPS response. |
| Morton 2018 · Br J Sports Med | meta-analysis | supports | high | 49-study meta-regression: fat-free-mass gains plateaued at about 1.62 g/kg/day; protein-supplement breakpoint effect had p=0.079 (not significant), confirming Topol's caveat that even the 1.6 figure is statistically fragile. |
| Ioannidou 2024 · J Nutr Health Aging | RCT | mixed | moderate | 12-week RCT in postmenopausal women found the high-protein arm did not consistently exceed adequate-protein controls, aligning with diminishing returns. |
| Huang 2021 · Nutrients | meta-analysis | mixed | moderate | Meta-analysis in older adults found modest milk-protein augmentation of resistance-training lean-mass gains, with several whey studies showing no added effect, indicating benefit saturates. |
| Kanaan 2025 · Eur J Clin Nutr | RCT | mixed | moderate | Study in recreational athletes under energy restriction examined whether protein above 1.2-1.7 g/kg better preserves fat-free mass, reflecting that in energy deficit higher intakes may add benefit. |
| Tagawa 2022 · Sports Med Open | meta-analysis | supports | high | Dose-response meta-analysis found total protein increased muscle strength with resistance training but with diminishing returns as intake rose, consistent with a plateau at moderate-to-higher intakes. |
| Davis 2026 · J Diet Suppl | meta-analysis | mixed | moderate | Meta-analysis (12 RCTs) found whey/soy supplementation did not significantly increase lean body mass in young trained adults, consistent with limited marginal benefit above adequate intake. |
Disagree, or know a study we missed?
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Educational only, not medical advice. Grades and scores reflect published evidence weighted by study design and quality; see the methodology.