Daily protein target tuned to your weight, goal, training status, and age — with a per-meal split and the leucine threshold that triggers muscle protein synthesis. The single most important macro for body composition, especially on a GLP-1.
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A single-meal target of 36 g could be:
Phillips 2016 and the Morton meta-analysis (2018, 49 studies, 1863 participants) converge on 1.6 g/kg as the threshold above which additional protein no longer meaningfully accelerates lean-mass gain in resistance-trained populations. Below this, you leave gains on the table.
Semaglutide and tirzepatide drive 25–40% of weight loss as fat-free mass. The protein floor matters more in caloric deficit, and more again when appetite is pharmacologically suppressed. See the GLP-1 weight-regain piece.
MPS (muscle protein synthesis) is triggered when leucine crosses a threshold of roughly 2.5 g per meal. That's ~25–30 g of high-quality protein (whey, eggs, chicken, fish, Greek yogurt). Distribute across 3–5 meals — not one giant evening dose.
Estimates a daily protein target for body composition and lean-mass preservation. Not a clinical prescription. Adults with chronic kidney disease, eating-disorder recovery, or specific medical conditions should set protein targets with a clinician — the numbers here assume otherwise-healthy physiology.
The RDA (0.8 g/kg) prevents deficiency but is below optimal for body composition, satiety, and aging. Current evidence supports 1.2–1.6 g/kg for general health and active adults, 1.6–2.2 g/kg for resistance trainees seeking muscle gain, and 1.6–2.4 g/kg for older adults (60+) to offset anabolic resistance. The calculator above maps your inputs to a target in that range.
For lean and normal-weight individuals: total body weight works fine. For people with significant excess body fat: lean mass (or 'goal weight') gives a more accurate target — you don't need to feed fat tissue protein. A rough adjustment: subtract 25–30% of body weight if you're well above your goal weight, then use that adjusted number with the gram/kg multiplier.
Muscle protein synthesis (MPS) plateaus at roughly 0.4 g/kg per meal in young adults and ~0.6 g/kg per meal in older adults — meaning more than that in a single sitting doesn't add more MPS, it just gets oxidized for energy. Practically: spread protein across 3–4 meals of 30–50 g each. The calculator shows a per-meal distribution suggestion.
In healthy kidneys: no. Multiple meta-analyses (including Devries et al., 2018, J Nutr) find no measurable decline in eGFR from high-protein intake in adults without pre-existing kidney disease. The 'protein damages kidneys' belief originated from studies in people with chronic kidney disease, where protein restriction is appropriate. Healthy kidneys handle 2+ g/kg routinely.
For total daily protein and muscle protein synthesis: animal sources (whey, eggs, dairy, meat) and well-formulated plant sources (soy, pea+rice combos) both work, with animal sources generally requiring less total grams to hit MPS thresholds due to higher leucine content. For health markers, gut, and longevity outcomes: more nuanced — some evidence favors mixed sources with adequate fiber and unprocessed plant inclusion.
The 'anabolic window' of 30 minutes post-workout is largely overstated. What matters more is total daily protein and getting a protein-containing meal within 3–5 hours before or after training. Shakes are convenient, not magic — if your meal timing already covers the bases, you don't need one.
GLP-1 medications suppress appetite, making it easy to under-eat protein and lose excessive lean mass (15–40% of total weight lost can be muscle on these drugs). The fix: prioritize protein to ≥1.6 g/kg of goal body weight from day one, regardless of low appetite. Combined with resistance training, this dramatically preserves lean mass during GLP-1 weight loss.