- Grade B
Per-meal protein threshold for muscle protein synthesis: the 30 g / leucine-trigger rule
Muscle protein synthesis (MPS) follows a threshold, not a linear dose-response: below roughly 2.5–3 g of leucine per meal (~30 g of high-quality protein), MPS is sub-maximally stimulated. Total daily protein is necessary but insufficient — distribution across meals determines how much of that protein actually builds and preserves lean mass.
Last reviewed:
- Grade A
Why the 0.8 g/kg protein RDA systematically underestimates true requirements
The current US protein RDA of 0.8 g/kg/day was derived from short-term nitrogen-balance studies that systematically undercount nitrogen losses and target deficiency prevention, not physiological optimization. Modern tracer methods (IAAO and stable-isotope techniques) consistently yield protein requirements 25–50% higher than nitrogen-balance estimates, placing the true minimum closer to 1.0–1.2 g/kg for sedentary adults and higher for active or aging populations.
Last reviewed:
- Grade B
Daily protein target of 1.6 g/kg ideal body weight for patients on GLP-1 medications
Patients on GLP-1 receptor agonists benefit from 1.2–1.6 g of protein per kg of ideal body weight per day, distributed across at least two meals containing ≥30 g each. This target sits well above the 0.8 g/kg RDA, reflects the anabolic demand of a sustained caloric deficit, and is supported by converging meta-analysis, position-stand, and clinical-trial evidence.
Last reviewed:
- Grade Bcross-filed
Anabolic resistance in aging and the elevated protein requirement for older adults
Older adults require more protein per meal than younger adults to achieve the same muscle protein synthesis response — a phenomenon known as anabolic resistance. Per-meal requirements rise from roughly 0.24 g/kg in young adults to 0.40 g/kg or higher after age 60, and daily targets of 1.2–1.5 g/kg/day are needed to correct the ~1–2 %/year muscle loss otherwise observed after age 60.
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