How Much Protein Do You Actually Need Per Kilogram? (Ending the 1.2 vs. 2.2 Debate)

Where does the '0.8g/kg' number actually come from?

That's the RDA, calculated to prevent deficiency in the general population — not a muscle-building target. The official Recommended Dietary Allowance of 0.8 grams per kilogram of body weight (or ~0.36g/lb) was established by nutrition governing bodies to satisfy the basic amino acid requirements of 97.5% of sedentary adults and avoid nitrogen imbalance.

Applying 0.8g/kg to someone lifting weights three to five days a week confuses a zero-deficiency baseline with an adaptation target. While 0.8-1.2g/kg keeps a non-lifter out of nitrogen deficit, it falls well short of the rate required to maximize muscle protein synthesis under heavy mechanical tension.

Where does '1g per pound' (2.2g/kg) come from?

It is a bodybuilding culture heuristic, not derived from the meta-analytic ceiling. For decades, gym culture promoted “1 gram of protein per pound of body weight” (2.2g/kg) because the math was simple, memorable, and guaranteed that lifters would never fall short of their amino acid needs.

While eating 2.2g/kg is generally safe for healthy individuals, treating it as an absolute floor creates unnecessary dietary friction. Research demonstrates that intake levels above 1.6-2.0g/kg do not yield measurable additional muscle mass for the vast majority of natural lifters.

What does the actual research say the ceiling is?

The comprehensive meta-analysis by Morton et al., 2018 (PMID 28698222), evaluated 49 randomized controlled resistance training trials involving 1,863 healthy adult participants. The statistical ceiling identified across the pooled data was approximately ~1.6g/kg/day (0.73g/lb).

Beyond 1.6g/kg/day, the upper bound of the 95% confidence interval in the Morton meta-analysis reached 2.2g/kg/day, but the average point of diminishing returns flattened at 1.62g/kg. Consuming more than this amount did not lead to statistically significant increases in resistance-training-induced fat-free mass accretion.

Does the target change with age or training experience?

The Morton meta-analysis found protein-supplementation efficacy decreases with age and increases with training experience — highly relevant for lifters managing training recovery over 40. Older adults experience anabolic resistance, meaning higher per-meal leucine thresholds are required to trigger equivalent muscle protein synthesis rates.

Because anabolic sensitivity diminishes with age, hitting a reliable floor of 1.6-2.0g/kg/day becomes even more essential for men over 40 to preserve lean tissue during fat loss or recomp phases. See our full guide on building muscle after 40 for age-adjusted protein distribution strategies.

So what number should I actually use?

Aim for 1.6-2.0g/kg/day (0.73-0.91g/lb) as a consistent daily floor rather than a number to maximize. This gives you the full meta-analytic benefit plus a conservative safety margin for high-stress or deficit days.

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