How It Works
Gist calculates your biological age by analyzing health metrics from Apple Health and comparing them against research-backed optimal ranges.
Unlike your chronological age (years since birth), biological age reflects how well your body is actually functioning. A 40-year-old with excellent health markers might have a Gist Age of 35.
Step 1
Data Collection
Gist reads from Apple HealthKit. Works with Apple Watch, Oura, Whoop, Garmin, Fitbit, and any device that syncs to HealthKit.
Step 2
Metrics & Optimal Ranges
Each metric is scored 0-100 based on how close you are to the optimal range. Higher-weighted metrics have more impact on your score.
Sleep
Quality rest is foundational to cellular repair and longevity.
| Metric | Optimal Range | Weight |
|---|---|---|
| Sleep Duration | 7-9 hours | 3x |
| Deep Sleep | 15-25% | 2x |
| REM Sleep | 20-25% | 2x |
Activity
Regular movement keeps your cardiovascular system young.
| Metric | Optimal Range | Weight |
|---|---|---|
| Daily Steps | 7,000-12,000 | 3x |
| Active Energy | 300-600 kcal | 2.5x |
| Exercise Time | 30-60 min | 2.5x |
| Distance | 5-10 km | 1x |
| Flights Climbed | 5-15 floors | 1x |
| Stand Hours | 10-14 hours | 1x |
Heart
Heart rate variability is one of the strongest predictors of biological age.
| Metric | Optimal Range | Weight |
|---|---|---|
| Resting Heart Rate | 50-65 bpm | 3x |
| HRV (SDNN) | 40-100 ms | 3x |
| Walking Heart Rate | 80-110 bpm | 1x |
| Respiratory Rate | 12-16 breaths/min | 1x |
Body
Physical fitness markers that correlate with longevity.
| Metric | Optimal Range | Weight |
|---|---|---|
| VO2 Max | 40-55 mL/kg/min | 3x |
| Walking Speed | 2.5-4.0 mph | 1x |
| BMI | 18.5-24.9 | 1x |
| Body Fat | 10-25% | 1x |
Step 3
Scoring
Standard Scoring
Within optimal range = 100 points. Outside the range = penalty based on how far you deviate.
Lower-is-Better
For metrics like resting heart rate: at or below the lower bound = 100 points.
Higher-is-Better
For metrics like HRV and VO2 Max: at or above the upper bound = 100 points.
Time Windows
Daily metrics (sleep, steps, heart rate) use a 7-day average. Body metrics (BMI, VO2 Max) use the latest value within 30 days.
Step 4
The Formula
Gist Age = Chronological Age + Age Offset
Age Offset = (50 - Overall Score) / 5
| Score | Age Offset | Meaning |
|---|---|---|
| 100 | -10 years | Exceptional health |
| 80 | -6 years | Excellent health |
| 50 | 0 years | Average health |
| 20 | +6 years | Below average |
| 0 | +10 years | Poor health markers |
Bonus
Pace of Aging
Beyond your Gist Age, we calculate your pace of aging—are you aging faster or slower than normal?
| Score | Pace | What it Means |
|---|---|---|
| 100 | -1.0x | Aging in reverse |
| 90 | -0.5x | Significant reversal |
| 80 | 0x | Stable / not aging |
| 65 | 0.5x | Aging slower than normal |
| 50 | 1.0x | Normal aging rate |
| 25 | 2.0x | Aging twice as fast |
| 0 | 3.0x | Accelerated aging |
Research
References
The optimal ranges used in Gist are based on established health research.