Which calorie tracker syncs with Apple Health and Apple Watch?

Both directions, but not everything. To Apple Health, Kairo writes each meal once its analysis is done: energy in kilocalories plus protein, carbohydrates and fat. Change a portion and the Health record is updated; delete the meal and it disappears there too. From Apple Health, Kairo reads two things: the active energy that iPhone and Apple Watch record as burned, and your body weight, so you never enter it twice.

Sync runs while the app is in the foreground: on open, on return, and when you pull to refresh on the home screen. There is no background delivery: Kairo does not wake itself to read Health. That is a deliberate choice for battery and transparency, and it means a Watch workout shows up the next time you open the app. HealthKit data is processed on your device and is not sent to our servers unless a feature needs it, as our privacy policy states.

It is a standalone watchOS app, not a mirrored widget. The overview shows calorie and macro rings for the day with your streak underneath. Quick add logs a meal straight from your wrist, and a list of recently eaten foods turns the breakfast you have every day into two taps. Complications show the day's status on the watch face without opening the app, updated after each sync with the iPhone.

The Watch and Health halves work together: the active energy your Watch measures flows into Kairo as burned calories, and everything you log on the wrist lands in the same history as the photo scans from your phone. What no Watch does, Kairo's included, is scan a plate. There is no usable camera, and no maker advertises it.

This is where Health sync often hurts more than it helps. Many apps add the Watch's active energy straight onto the food budget: a 600 kcal run, 600 kcal more to eat. But the Watch estimates that burn, and depending on the activity it estimates generously. That applies to every app that works this way, including Kairo: once you connect Apple Health, the day's active energy raises your daily goal by the same amount. The app says so next to the switch, so a growing goal does not look like a bug.

The counterweight is the scale. Kairo can measure your baseline need from your weight trend and actual intake once there is enough data (at least eight weigh-ins across two weeks and ten fully logged days) and then suggests an adjusted goal. If your weight stays flat for weeks while the Watch and the scan insist you are in a deficit, that shows up in the suggestion. Nothing changes without your approval.

MyFitnessPal syncs bidirectionally with Apple Health and is broad about it (nutrition, weight, activity), a real advantage if Health is your central store; its Watch support runs mainly through Health rather than a deep native logging app. Lose It! has a Watch app and HealthKit sync, and one comparison describes the Watch function as limited. Cronometer's listing explicitly mentions syncing with Apple Health and Apple Watch; its strength remains its nutrient depth (up to 95 values). Cal AI has a HealthKit integration but advertises no dedicated Apple Watch logging app.

These are listing facts and user reports, not a test we ran. What you can verify yourself: in Apple Health under "Sources", each app shows which categories it reads and writes.

Kairo asks for permission the first time it needs it; you choose separately whether it may write nutrition, read energy and read weight, and you can change or revoke each later in Apple Health under "Data Access & Devices". One tip that applies to every app: let only one tracker write nutrition data. If two apps write, every meal shows up twice in Health while you are comparing them.

For whom is it worth it? For weight loss, yes: the weight import is the feedback that keeps the photo scan honest. For athletes, yes, to see burn and intake in one place with the caveat that both are estimates. Kairo works fully without any Health permission; the sync is an add-on that improves the numbers, not a requirement. Kairo is iOS-only (iPhone and Apple Watch, iOS 16.4 or later); on Android, MyFitnessPal, Lose It! and Cronometer are the options.

On cost: the Watch app and Health sync are part of Kairo's single subscription: $3.99 per week or $44.99 per year (3,99 € / 49,99 € in Germany), with a 3-day free trial on the yearly plan only. Barcode lookups are unlimited and three AI analyses per account work without a subscription; after that you need one. Details are on the pricing page. MyFitnessPal, Lose It! and Cronometer have permanent ad-funded free tiers and are cheaper to start with.