The TL;DR
IGF-1 is a hormone that makes things grow. In childhood, it drives height and development. In adulthood, it builds muscle and bone. However, high levels of IGF-1 are linked to accelerated aging and cancer risk, while low levels are found in centenarians. The goal is a “Goldilocks” zone: enough to prevent frailty, but low enough to slow aging.
Accessibility Level
Level 1 (Foundation): Tested in standard blood panels. Understanding your levels helps you dial in your protein intake and fasting protocols.
The Science of Growth vs. Longevity
The Trade-off
Evolution cares about you reproducing, not living to 100.
- High IGF-1: Great for muscle, libido, and energy (reproductive fitness).
- Low IGF-1: Great for DNA repair and stress resistance (somatic maintenance).
In nature, organisms that grow fast (high IGF-1) die young. Organisms that grow slow (low IGF-1) live long.
The Laron Dwarfs
A group of people in Ecuador with a genetic mutation that causes very low IGF-1 (Laron Syndrome) are extremely short but are virtually immune to cancer and diabetes. This is the strongest human evidence that lowering the “growth signal” protects against age-related disease.
The Cancer Connection
Cancer is uncontrolled cell growth. High IGF-1 is like throwing gasoline on a fire—it inhibits apoptosis (programmed cell death), allowing damaged (precancerous) cells to survive and multiply.
Evidence Matrix
| Source | Verdict | Notes |
|---|---|---|
| Valter Longo | Low IGF-1 | Leading researcher showing low protein/IGF-1 extends lifespan in multiple species. |
| Cynthia Kenyon | Low IGF-1 | Her work on C. elegans showed that reducing insulin/IGF-1 signaling doubled lifespan. |
| Peter Attia | Nuanced | Warns against driving IGF-1 too low in the elderly, as sarcopenia (muscle loss) kills faster than cancer. |
Optimal Ranges
| Population | Target (ng/mL) | Strategy |
|---|---|---|
| Young/Active | 150 - 250 | Support muscle growth and athletic performance. |
| Longevity Focused | 100 - 150 | The sweet spot for reduced aging risk without frailty. |
| Cancer Survivor | < 100 | Strict minimization often recommended (consult oncologist). |
(Note: IGF-1 levels naturally decline with age. A level of 120 is “high” for an 80-year-old but “low” for a 20-year-old).
How to Optimize
To Lower IGF-1 (Anti-Aging Mode)
- Protein Restriction: Specifically restricting animal protein and methionine lowers IGF-1.
- Fasting: Prolonged fasts (>24 hours) dramatically drop IGF-1.
- Carbohydrate Restriction: Insulin and IGF-1 are linked; lowering insulin often lowers IGF-1.
To Raise IGF-1 (Performance Mode)
- High Protein: Eat 1g/lb of body weight.
- Heavy Lifting: Systemic stress signals the liver to produce more IGF-1.
- Sauna: Heat stress boosts Growth Hormone (the precursor to IGF-1).
The Strategy: Cycling
Don’t be in “growth mode” 24/7. Use Fasting Mimicking Diets or periodic low-protein cycles to clear out damage, then re-feed to build muscle.
References
Guevara-Aguirre, J., et al. (2011). Growth hormone receptor deficiency is associated with a major reduction in pro-aging signaling, cancer, and diabetes in humans. Science, 3(70), ra13.
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, 19(3), 407-417.
Bartke, A. (2008). Insulin-like growth factor 1 and aging. Endocrine Reviews.