Privacy Policy — Bread or Butter
Effective date: July 20, 2026
Bread or Butter is an Apple Watch app with an iPhone companion. It estimates your fat‑vs‑carbohydrate fuel mix and heart‑rate zones from your heart rate. This policy explains what data the app uses and how it is handled.
Data the app reads
With your permission, Bread or Butter reads the following from Apple Health (HealthKit) on your Apple Watch and iPhone, read‑only:
- Heart rate — to show your current effort and fuel mix.
- Resting heart rate — to estimate your heart‑rate zones.
- Date of birth — to estimate your maximum heart rate (220 − age).
On the Apple Watch, the app reads live heart rate while a workout is recording (for example, in Apple's Workout app). The iPhone companion reads your resting heart rate, most recent heart rate, and date of birth to show your heart‑rate zones. The app does not write any data to Apple Health.
How your data is used
- All calculations happen on your device. Your health data is used only to display your live fuel mix, heart rate, and zone.
- Any settings you enter (heart‑rate overrides and the optional medication offset) are stored locally on your device.
What we do NOT do
- We do not collect, transmit, sell, or share your health data.
- We do not send your data to any server, and the app has no analytics, tracking, advertising, or third‑party SDKs.
- We do not use HealthKit data for advertising or marketing, and we do not share it with third parties.
- There is no account and no sign‑in.
Because your data never leaves your device, we have no access to it.
Not medical advice
The fat/carb split and heart‑rate zones are rough, textbook‑based estimates for general interest and are not medical advice. Do not use them for diagnosis or treatment decisions. Consult a qualified professional for medical guidance.
Children
The app is not directed to children and does not knowingly collect data from anyone.
Changes
If this policy changes, the updated version will be posted at this URL with a new effective date.
Contact
Questions? Contact the developer at cmatsoukis@gmail.com.