# Bread or Butter — Your fat-vs-carb fuel gauge > Live heart rate fuel gauge for fat vs. carb usage during workouts. (iPhone/iPad app by christian Matsoukis.) - Source: https://appshunter.io/ios/app/bread-or-butter/id6792948473 (this page in markdown: same URL + `.md`) - Developer: [christian Matsoukis](https://appshunter.io/developer/835090494) - Category: Health & Fitness, Entertainment - Price: Free - Rating: 5.00/5 from 1 App Store ratings · 1 written reviews indexed - Age rating: 4+ - Requires: iOS 18.0 · 2 MB - Languages: American English - Released: 2026-07-24 - Data updated: 2026-08-26 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/bread-or-butter/id6792948473/reviews.md ## What is Bread or Butter? Butter or bread? See what your body is burning. Bread or Butter turns your live heart rate into a cute, glanceable fuel gauge: a stick of butter (fat) and a French baguette (carbs) meet at a sliding divider that shows your estimated fat-vs-carb mix as you move. Ease off and the butter grows; push harder and the bread takes over. HOW IT WORKS • Start a workout in Apple's Workout app, then open Bread or Butter • It reads your live heart rate and maps your intensity to an estimated fat/carb split using the classic "crossover" curve. • See your current BPM and heart-rate zone (1–5), based on your heart-rate reserve (Karvonen). FEATURES • A playful butter-and-baguette ratio bar with smooth animation • Heart-rate zones from your resting heart rate and age — read automatically from Health, or set your own in Settings • Medication offset: if a stimulant raises your heart rate, subtract a few BPM so your zones reflect true effort • Private by design: everything stays on your Apple Watch. No account, no tracking, no ads. Bread or Butter is made for curiosity and motivation — not medical use. The fat/carb split and heart-rate zones are ballpark, textbook estimates, not measurements or medical advice. ## Key features - Glanceable fuel gauge visualization - Estimates fat vs. carb burn - Live heart rate monitoring - Heart rate zone display - Private by design, no tracking - Medication offset feature ## Recent user reviews (1 of 1) All indexed reviews: https://appshunter.io/ios/app/bread-or-butter/id6792948473/reviews.md ### 5/5 — LOVE! *2026-07-25* I love this app so far! It’s super cute and helpful ## Frequently asked questions about Bread or Butter ### What is Bread or Butter? Bread or Butter is a health and fitness app that visualizes your body's estimated fat vs. carb fuel usage during workouts. It uses your live heart rate to display this information in a playful, glanceable format. ### How does Bread or Butter estimate fat vs. carb burn? The app reads your live heart rate and maps your intensity to an estimated fat/carb split using the classic "crossover" curve. It also displays your current BPM and heart-rate zone based on your heart-rate reserve. ### Is Bread or Butter accurate for medical advice? No, Bread or Butter is designed for curiosity and motivation, not medical use. The fat/carb split and heart-rate zones are ballpark, textbook estimates and should not be considered measurements or medical advice. ### Does Bread or Butter have ads? No, Bread or Butter is ad-free. The app is designed with privacy in mind, keeping all data on your Apple Watch and not tracking users. ### What devices is Bread or Butter compatible with? Bread or Butter is available for Apple Watch and iPhone. It integrates with Apple's Workout app to read live heart rate data. ### How often is Bread or Butter updated? The latest version of Bread or Butter is 1.1, which was last updated on August 19, 2026. Updates typically include improvements and new features. ### Can I adjust my heart rate zones in Bread or Butter? Yes, you can set your own heart-rate zones in Settings, or they can be read automatically from Health based on your resting heart rate and age. There is also a medication offset feature to adjust for stimulants. ### What do users like about Bread or Butter? Based on its 5.0-star rating from 1 review, users likely appreciate the playful and unique visualization of workout intensity, the privacy-focused design, and the motivational aspect of seeing their fuel gauge. ## Version history (last 2 releases) ### 1.1 — 2026-08-19 Connect a Bluetooth heart-rate strap (like a Polar H10) to see your fuel mix live — on your watch or iPhone, no workout needed. The iPhone becomes a live gauge of its own when a strap is connected. Added an optional tip jar, too, if you'd like to say thanks. ### 1.0 — 2026-07-25 No release notes. ## More apps by christian Matsoukis - [Sewer Rat](https://appshunter.io/ios/app/sewer-rat/id846800940) All apps by christian Matsoukis: https://appshunter.io/developer/835090494 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-26.*