Body Mass (Weight)
Definition
Total body mass, typically measured in kilograms or pounds.
Why It Matters
Weight is a fundamental health metric: - Cardiometabolic risk - Both under- and overweight increase risks - Treatment decisions - Many medications dosed by weight - Nutritional status - Indicator of energy balance - Disease monitoring - Weight changes can indicate health issues - Fitness tracking - Context for training and body composition
How It's Measured
- Digital scales - Most common home method
- Smart scales - Sync directly to HealthKit
- Clinical scales - More precise, used in medical settings
- Manual entry - User-logged in Apple Health
Reference Guidance
Weight alone is less informative than: - BMI (weight for height) - Body composition (fat vs lean mass) - Trend over time (stable, gaining, losing)
Important: "Ideal weight" is highly individual and depends on: - Height - Body composition - Age - Activity level - Health conditions
Confounders & Limitations
- Time of day - Weight fluctuates 1-2 kg daily
- Hydration - Fluid shifts affect weight
- Clothing - Consistent measurement conditions matter
- Food/drink timing - Recent meals affect readings
- Menstrual cycle - Water retention causes fluctuations
- Scale accuracy - Varies between devices
Best Practices for Tracking
- Weigh at same time daily (morning, after bathroom)
- Use same scale consistently
- Wear similar clothing (or none)
- Focus on weekly averages, not daily fluctuations
- Consider trends over 2-4 weeks
Use Cases
- Health monitoring - Tracking weight changes
- Weight management - Goals for gain or loss
- Medical context - Medication dosing, health assessments
- Fitness tracking - Combined with body composition