Do You Really Need 2g of Protein per kg of Bodyweight? Common Wisdom vs. the Research
Published: 2026-06-25
Written by: Shingo YoshizakiReviewed by: Tomonobu Someda
"Eat 2g of protein per kg of bodyweight" is one of the most repeated nutrition rules in any gym. But does the science actually back that number, or is it overcautious bro-math? We put the claim through three rounds against the meta-analytic evidence.
Let the data settle it.
Is 2g/kg of protein actually necessary for muscle hypertrophy?
What's said
ジムやSNSで広く流布されている通説
If you're serious about building muscle, 2g per kg is the baseline — anything less and you're leaving gains on the table. Pros and amateurs alike swear by this number.
What research says
- A meta-analysis by Morton et al.
- (2018) covering 49 studies and over 1,800 participants found that the muscle-building effect of protein supplementation plateaus at approximately 1.62 g/kg/day.
- At 2 g/kg you are slightly above that ceiling, and the marginal gain in lean mass beyond ~1.62 g/kg is negligible or statistically non-significant.
- Individual variation in genetics, training age, and age itself does exist, so targeting 2 g/kg as a practical buffer is not harmful — but it is not strictly necessary.
For healthy resistance-trained individuals, 1.6–1.8 g/kg captures most of the hypertrophy benefit. The 2 g/kg figure works as a practical upper ceiling with a safety buffer, not a strict requirement.
Are there any benefits to going beyond 2g/kg?
What's said
ボディビルダーのSNS・ブログ等
More is more. Protein is harder to store as fat, keeps you full, and some elite athletes eat 3–4g/kg. Why cap yourself?
What research says
- Reviews including Stokes et al.
- (2018) confirm that protein has a high thermic effect and is less readily stored as fat, but the ceiling on muscle protein synthesis means intake well above 2 g/kg (e.g., 3+ g/kg) adds calories without a proportional hypertrophy benefit.
- Safety in adults with normal kidney function is generally supported, but the cost-to-benefit ratio deteriorates and total caloric balance becomes harder to manage.
Substantially exceeding 2 g/kg is safe for healthy adults with normal kidney function, but adds no meaningful hypertrophy benefit. It can actually work against you by crowding out caloric balance and dietary variety.
Should protein targets differ between a cut and a bulk?
What's said
ジムの一般的なアドバイス
Just keep it at 2g regardless — whether you're cutting or bulking, that number covers everything.
What research says
- A systematic review by Helms et al.
- (2014) of lean, resistance-trained athletes under caloric restriction found that 2.0–2.4 g/kg is advisable during a cut, with higher intakes warranted at lower body-fat levels.
- In a caloric deficit, some dietary protein is diverted to energy metabolism rather than muscle protein synthesis, raising the effective requirement.
- During a caloric surplus (bulk), the evidence generally supports 1.6–2.0 g/kg as sufficient.
During a bulk, 1.6–2.0 g/kg is adequate. During a cut, bumping to 2.0–2.4 g/kg supports muscle retention. The right answer is context-dependent, not a single fixed number.
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Published: 2026-06-25
Written by
Shingo YoshizakiSoftware Engineer / Research Writer at BODYDATA
An engineer's job is verification. I read the source before I trust gym lore — same as code.
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Reviewed by: Tomonobu Someda
Content reviewed from the perspective of coaching practice and supplement-industry experience