Summary:
Expanding HealthKit to support the full spectrum of smart scale metrics will allow Apple Health to remain the central hub for health data, align with user expectations, and future-proof the framework as body composition analysis evolves.
Description:
With the growing adoption of smart body composition scales (e.g. segmental impedance scanners, multi-frequency analyzers, and body pods), users are generating a wide variety of clinically relevant metrics that currently cannot be stored natively in HealthKit.
At present, HealthKit supports a core set of body composition values (Body Mass, BMI, Body Fat %, Lean Mass, Height, Waist Circumference). While useful, these do not capture the full picture modern devices provide, leading to fragmentation:
• Users can see dozens of metrics in the device app, but only a handful flow into Health.
• Developers must resort to metadata fields, which are inconsistent across apps and not accessible in Apple’s Health app UI.
This gap undermines HealthKit’s role as a central, standardized health record.
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Proposed Additions:
Expand HealthKit HKQuantityTypeIdentifier to include additional body composition and derived measurements commonly reported by smart scales:
Core Body Composition
• Visceral fat percentage / rating
• Skeletal muscle mass
• Segmental muscle mass (arms, legs, trunk)
• Segmental fat mass (arms, legs, trunk)
• Bone mineral mass
• Total body water % / hydration
Derived Health Metrics
• Muscle-to-fat ratio
• Phase angle (bioelectrical impedance)
• Metabolic age
• Basal metabolic rate (BMR)
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Rationale:
• User benefit: Health app would show a more complete health profile, not just weight and fat %.
• Developer benefit: Creates standardized identifiers, eliminating the need for proprietary storage in metadata.
• Industry alignment: Many leading health devices already provide these metrics; users expect them to sync into Health.
• Future-proofing: As body scanning scales proliferate, HealthKit can remain the trusted central repository rather than ceding ground to siloed vendor apps.
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Suggested Implementation:
• Introduce new HKQuantityTypeIdentifier values for each metric.
• Permit segmental values to be represented as discrete samples with metadata for body region.
• Ensure values can be written by apps/devices and surfaced in Health app UI, just like existing body composition data.