The metabolic age calculation utilizes physiological data that has been proven in medical literature to have a strong correlation with aging, mortality risk, and metabolic health.
Basic Data: Gender, age, height, and weight.
Clinical and Wearable Data:
· Cardiorespiratory Fitness: VO2 Max [1, 2], Resting Heart Rate (RHR) [3], and Heart Rate Variability (HRV) [4].
· Metabolic Indicators: Body Fat Percentage [9, 10], Blood Glucose / HbA1c [13], and Blood Lipids (Cholesterol/Triglycerides) [12].
· Lifestyle and Vital Signs: Sleep Duration [5, 6], Physical Activity (Steps/Exercise) [7, 8], Blood Pressure [11], CRP (Inflammation) [14], and Respiratory Parameters (SpO2, Respiratory Rate) [15].
Basal Metabolic Rate (BMR) Calculation
The foundation of the calculation lies in the body's resting energy expenditure. Different clinically accepted equations are used at this stage:
· Baseline Calculation: The Harris-Benedict equation is used for general population standards.
· Personalized Reporting: The Mifflin-St Jeor equation is used for user-specific analysis.
· Body Composition Effect: When body fat percentage data is available, the Katch-McArdle approach is used to refine the calculation by accounting for the muscle-fat balance.
Baseline Metabolic Age
Baseline metabolic age is derived by harmonizing the individual's biological data with a standard physical activity level (PAL) assumption.
· The raw BMR value is processed with standard activity coefficients to find the Estimated Total Energy Expenditure (TEE).
· This value is reverse-solved according to age using scientific energy requirement equations published by the National Academies of Sciences, Engineering, and Medicine (NASEM) to determine the "theoretical baseline age" [16].
Physical Activity Level (PAL) Effect
If the user has not entered manual activity data, a dynamic PAL estimation is made using step count, VO2 max, and resting heart rate data from wearable devices.
· Regular physical activity is known to reduce mortality risk and improve metabolic health [7, 8].
· The calculated activity level does not directly change the baseline age; instead, it is included in the calculation as an "aging penalty" for inactivity or a "rejuvenation bonus" for high activity.
Biological Differences (Deltas)
The most critical factor determining the final metabolic age is how much the individual's clinical and physical measurements (Deltas) deviate from scientific norms.
· Wearable Device Data: Sleep quality [5, 6], heart rate, and activity data are analyzed.
· Clinical Health Measurements: Blood values and body composition are examined.
· Each metric creates an aging or rejuvenating effect on metabolic age by comparing it against ideal ranges and risk thresholds defined by relevant health authorities [11, 14].
Domain-Based Soft Cap
To maintain consistency, contributing factors are grouped into specific health domains:
· Cardiovascular Health
· Metabolic Control
· Blood Pressure & Circulation
· Renal & Respiratory Functions
A maximum effect limit is applied to each domain group to prevent a single data point from excessively dominating the result.
Body Composition Protection Mechanism
Body Mass Index (BMI) alone may be insufficient to reflect metabolic health [9]. If the user's body fat percentage data is missing and the BMI value is high, the system automatically applies a "protection mechanism." This approach prevents skewed results in cases where individuals with high muscle mass cannot be distinguished from those with high body fat.
References;
1. Kaminsky LA, et al. Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing. Mayo Clin Proc. 2015.
2. Kodama S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality. JAMA. 2009.
3. Olshansky B, et al. Importance of resting heart rate. Trends Cardiovasc Med. 2023.
4. Umetani K, et al. Twenty-four hour time-domain HRV and heart rate: relations to age and gender. J Am Coll Cardiol. 1998.
5. Hirshkowitz M, et al. National Sleep Foundation's updated sleep duration recommendations. Sleep Health. 2015.
6. Che T, et al. The Association Between Sleep and Metabolic Syndrome: A Systematic Review. Front Endocrinol. 2021.
7. World Health Organization. WHO Guidelines on Physical Activity and Sedentary Behaviour. 2020.
8. Ding D, et al. Daily steps and health outcomes in adults: a dose-response meta-analysis. Lancet Public Health. 2025.
9. Baylor College of Medicine. Body Fat Percentage vs. BMI: Which is more important? 2023.
10. Kitahara CM, et al. Association of extreme obesity with all-cause mortality. PLoS Med. 2014.
11. Stamler J, et al. Blood Pressure in Adulthood and Life Expectancy. Hypertension. 2005.
12. National Library of Medicine. LDL Cholesterol: The 'Bad' Cholesterol. 2021.
13. Dal Canto E, et al. Diabetes as a cardiovascular risk factor. Eur J Prev Cardiol. 2019.
14. Pearson TA, et al. Markers of Inflammation and Cardiovascular Disease (CRP). Circulation. 2003.
15. Smith GB, et al. SpO2 values in acute medical admissions breathing air. Resuscitation. 2012.
16. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy. The National Academies Press. 2023.