The TL;DR
Protein is the structural material of your body. You need it to build muscle, neurotransmitters, and immune cells. In longevity, there is a tension: High protein prevents Sarcopenia (frailty), but excessively high protein (specifically amino acids like Methionine) activates mTOR, which can accelerate aging. The strategy? Cycle it. High protein to build, lower protein to clean.
Accessibility Level
Level 1 (Foundation): Getting protein right is the most critical dietary intervention for physical function.
The Science of Amino Acids
The Protein Leverage Hypothesis
Biological organisms will eat until they satisfy their protein requirements. If you eat low-protein food (chips), you will overeat calories to get enough amino acids. Prioritizing protein is the hack for weight management.
The Muscle vs. mTOR Dilemma
- Pro-Muscle: You need ~1.6g/kg of protein to maximize Muscle Protein Synthesis (MPS). Muscle is the organ of longevity.
- Pro-Longevity: Restricting protein (specifically Methionine and BCAAs) extends lifespan in mice by inhibiting mTOR and boosting autophagy.
- The Resolution: We are not mice living in a sterile cage. Humans die of frailty. For most, the risk of low muscle (Sarcopenia) outweighs the theoretical risk of mTOR activation.
The Anabolic Resistance of Aging
As you age, your muscles become “deaf” to protein signals. A 20-year-old needs 20g of protein to trigger growth; an 80-year-old might need 40g. You need MORE protein as you age, not less.
Evidence Matrix
| Source | Verdict | Notes |
|---|---|---|
| Peter Attia | High Protein | ”I have never seen a patient in their 80s die from ‘too much muscle’.” |
| Valter Longo | Low Protein | Advocates for lower protein (0.8g/kg) to suppress IGF-1 and cancer risk. |
| Stuart Phillips | Consensus | ~1.6g/kg is the sweet spot for muscle maintenance in active adults. |
Optimal Intake
| Goal | Target (g/kg bodyweight) | Target (g/lb) |
|---|---|---|
| Survival (RDA) | 0.8 g/kg | ~0.36 g/lb |
| Optimal (Active) | 1.6 - 2.2 g/kg | 0.7 - 1.0 g/lb |
| Elderly (>65) | > 1.2 - 1.5 g/kg | Need more to overcome anabolic resistance. |
(Example: A 180lb male should aim for ~140-180g protein/day).
How to Optimize
- Distribution: Don’t eat it all at dinner. Aim for 30-40g per meal to trigger the “Leucine Threshold” for muscle growth.
- Source: Animal protein (whey, eggs, meat) has higher bioavailability and amino acid density than plant protein. Plant-based eaters need to consume ~20% more total protein to match the anabolic effect.
- Cycling: Consider lower protein days during fasting periods to stimulate autophagy, then high protein days to rebuild.
References
Simpson, S. J., & Raubenheimer, D. (2005). Obesity: the protein leverage hypothesis. Obesity Reviews.
Phillips, S. M. (2014). A brief review of critical processes in exercise-induced muscular hypertrophy. Sports Medicine.
Levine, M. E., et al. (2014). Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population. Cell Metabolism.