What this means in practical terms
Free-plan advertising may involve device information, advertising identifiers, and general usage data, but your food logs, weight entries, and health integration data are treated differently. They are used for the product experience—logging, targets, trends, sync, and account features—not for ad targeting based on what you ate.
When you connect Apple Health / HealthKit on iPhone or Health Connect on Android, the underlying platform permission screens control what categories are shared. You can review or revoke those permissions from your phone settings.