Bodix uses Apple services where they help, instead of building a separate account system around your body data.
Apple Health can help you start with history
If Apple Health already contains your weight history, importing it can make Bodix useful right away because the app starts with history instead of an empty graph.
iCloud sync helps with continuity
When iCloud sync is available and enabled, Bodix can keep the same data available across your supported Apple devices.
That is useful for consistency, but Apple still controls the sync system.
Privacy still starts with your own device habits
Even with Apple services, your privacy still depends on basics such as device security, account protection, and careful handling of exported data.