How much protein do you need per day to build muscle?
About 1.6 g per kilogram of body weight per day. Beyond this threshold, no additional benefit for muscle mass has been demonstrated. For an 80 kg person, that's ~128 g of protein per day.
Protein intake is probably the most debated topic in strength training. And also the most polluted by supplement marketing. Here's what science actually says — and why even a great study doesn't replace observing your own body.
🔬 The Science: The Reference Meta-Analysis
In 2017, a team at McMaster University (Morton et al.) published in the British Journal of Sports Medicine the largest meta-analysis to date on this topic: 49 studies, 1,863 participants.
What the data confirms
- Protein supplementation significantly increases lean muscle mass and strength during training
- The effectiveness threshold is at ~1.62 g protein/kg/day
- Beyond this threshold, no additional lean mass gains were observed
⚠️ What most people don't know
- Protein effectiveness decreases with age (older individuals need more for the same effect)
- Already-trained individuals benefit more from supplementation than beginners
- Protein source (food vs supplement) has no significant impact on results
📊 Reference Table by Body Weight
| Body Weight | Minimum target | Optimal threshold (~1.6 g/kg) | Beyond (no benefit) |
|---|---|---|---|
| 130 lbs (60 kg) | ~90 g/day | ~96 g/day | > 100 g/day |
| 155 lbs (70 kg) | ~105 g/day | ~112 g/day | > 120 g/day |
| 175 lbs (80 kg) | ~120 g/day | ~128 g/day | > 140 g/day |
| 200 lbs (90 kg) | ~135 g/day | ~144 g/day | > 160 g/day |
| 220 lbs (100 kg) | ~150 g/day | ~160 g/day | > 180 g/day |
🧪 The Limits of This Study
What this meta-analysis doesn't perfectly capture
- Protein quality ignored in some studies: not all proteins are equal (essential amino acids, leucine, digestibility)
- Mostly male participants: women are underrepresented — their specific needs remain less documented
- Daily distribution not controlled: eating 160 g in one meal vs 4 meals makes a difference this meta-analysis doesn't evaluate
- Variable study durations: from 6 weeks to 1 year. Long-term effects (>2 years) are poorly documented
- Caloric context not standardized: a caloric deficit or surplus changes everything about protein utilization
📊 The Average Doesn't Represent You
1.62 g/kg/day is the average at which gains plateau in the studied population. It doesn't mean you max out at exactly this number. Some people may slightly benefit from 1.8-2g/kg in certain contexts:
Situations where slightly higher intake may be relevant
- Cut / caloric deficit: 1.8-2.2 g/kg helps preserve muscle mass when calories are low
- Very advanced athletes near their genetic potential, optimizing every detail
- Older adults (50+): anabolic resistance increases with age, needs may exceed 1.6 g/kg
- Post-injury recovery: protein needs increase during tissue rebuilding
🎯 How to Find YOUR Ideal Number
Practical 3-step protocol
- Step 1 — Base: Target 1.6 g/kg for 8 weeks. Track weight, strength, and recovery
- Step 2 — Test higher: Go to 2 g/kg for 8 weeks. Same observation protocol. Do you notice a real difference in mass, energy, satiety?
- Step 3 — Adjust to context: Bulk, cut, high-stress period — each context has specific demands
🚨 What supplements won't tell you
- Whey protein has no magic effect beyond filling a dietary protein gap
- If you already eat 160 g of protein through food, an extra shake won't add muscle
- Timing (pre/post workout) has a marginal effect — total daily intake is what truly matters
💡 Final Thoughts
Targeting 1.6 g/kg/day is a solid goal, validated by the largest existing meta-analysis. It's a reasonable, achievable target through diet without necessarily relying on supplements. But if you're in a caloric deficit, older, or in intense physical preparation, your body may legitimately need a bit more.
The real intelligence is understanding why this number exists, not blindly following it. Observe your body over 8-12 weeks. Data is a starting point — you are the final experiment.
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Smart Rabbit takes into account your weight, goals and context to tell you exactly how much protein you need each day.
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