A specific, widely repeated claim in gym culture says the body "can't use" more than roughly 20-40g of protein in a single sitting, and anything beyond that is wasted. This is a genuine misreading of real research, not a fabricated myth — which makes it worth untangling carefully.
Where the number comes from
Studies measuring muscle protein synthesis (MPS) — the rate at which muscle tissue is actively being built — after a single meal do show a plateau. A landmark study by Moore et al. (2009) and follow-up research found that MPS response to a meal levels off somewhere around 20-40g of high-quality protein (varying by study, protein source, and body size), with additional protein beyond that point producing little extra MPS stimulus in that specific 3-4 hour measurement window.
Why "wasted" is the wrong word
This is where the popular claim goes wrong: it conflates "no additional muscle-building signal in this measurement window" with "your body cannot absorb or use it." Digestion and amino acid absorption aren't capped at 30g — your gut absorbs essentially all the protein you eat, the way it does with other macronutrients. Amino acids beyond what's used for immediate muscle protein synthesis don't get flushed unused; they're used for other bodily protein needs (enzymes, immune function, other tissue repair), stored temporarily, or their nitrogen is processed and the carbon skeletons used for energy or converted to glucose.
What the research does support
The genuinely useful takeaway from this research isn't a hard per-meal ceiling — it's that spreading protein across 3-4 meals of 20-40g each stimulates muscle protein synthesis more consistently across a full day than concentrating the same total into one or two very large meals. See our protein timing guide for the fuller picture on distribution.
Practical takeaway
Eating 60g of protein in one meal isn't wasted — you'll still digest and use it. But if you have the flexibility to split it into two 30g meals instead, the research gives a modest edge to spreading it out.