Your 20s — Banking Health
The deposit decade
You're {chronoAge}. Almost everything your 70-year-old self needs — peak bone density, peak muscle mass, a strong VO2 max ceiling, an intact microbiome, undamaged sleep architecture — gets laid down in this decade. You can't undo what you don't build.
Peak bone mass is mostly done by 30
Roughly 90% of peak bone mass is achieved by age 20 in women and age 22 in men. By 30 it plateaus, then erodes ~1% per year (faster post-menopause). What you eat, lift, and jump now literally builds the skeleton you'll stand on at 80.
VO2 max has a ceiling you train early
Your trainable VO2 max ceiling is mostly set by your mid-20s. Early aerobic fitness creates mitochondrial density and cardiovascular structure you keep for life. Elite adults are almost always people who trained hard before 30.
The invisible wins
No smoking. Sunscreen. Hearing protection at concerts. No binge drinking. These don't feel like "longevity interventions" because they're just habits. They are interventions. The 70-year-old with good hearing, smooth skin, and clean lungs looks effortlessly lucky — but they made choices at {chronoAge}.
Peak bone mass closes around 30
Bone-mineral density peaks between 25 and 30, then plateaus, then slowly declines. The ceiling you reach in your 20s is largely the ceiling you live with — you can slow loss but rarely build new peak after 30. Weight-bearing impact (running, jumping, lifting) + 1200mg calcium + 2000+ IU Vit D in your 20s pays for the next 50 years of skeletal life.
Key Takeaway
Your 20s is the deposit decade. Build the bone, muscle, cardio ceiling, and habit stack now. You can't train peak bone mass at 60.