Straight answers. Yes, Cronometer syncs with Apple Health, in both directions: it exports 13 nutrients plus several biometrics and imports a long list including sleep, heart rate and blood glucose. MyFitnessPal writes meal summaries out but never reads food back in. MacroLog writes calories, protein, carbs, fat, 12 micronutrients, water and weight, reads weight two-way, and reads steps and active energy as information only. "Syncs with Apple Health" is a checkbox on every marketing page and it hides all of that.
MacroLog publishes this page and sells one of the eight apps below. The rival rows were built from each company's own help centre, blog or App Store listing on 10 September 2026, and every source is linked at the end. Two rows are marked "not published": we could not verify them today, and we did not fill the gap from third-party blogs.
The matrix
| App | Writes to Apple Health | Reads from Apple Health |
|---|---|---|
| MacroLog | Calories, protein, carbs, fat, 12 micronutrients, water, weight | Weight (two-way), steps and active energy as information only |
| Cronometer | General activity, 13 nutrients, blood glucose, body fat, body temperature, blood pressure, dietary cholesterol, height | General activity, exercise, height, sleep duration, sleep stage, sleep score, recovery score, heart rate, body temperature, body fat, blood pressure, blood glucose, weight, waist circumference |
| MyFitnessPal | Meal summaries: calories and some nutrients. Caffeine and vitamin A are not sent. Exercise is not exported. | Exercise logged the same day, weight, sleep. Food is never read back. |
| MacroFactor | Nutrition, added March 2022 for Apple Health and Google Fit; weight | Daily calories and macros, landing on the Nutrition page rather than the Food Log; weight; wearable expenditure |
| Lifesum | Food calories, food nutrition, weight, water intake | Exercise calories, steps, active calories, exercise time, workouts, weight |
| Noom | Reads and/or writes steps, weight, blood glucose, dietary energy, active energy, water, mindfulness minutes and exercise/movement. Noom's support page does not split those by direction. | |
| Cal AI | Connects from inside the app: swipe right on the calories screen, tap "Connect with Apple Health". The data types are not published. | |
| Lose It! | "Fitness App Syncs" is listed as a Premium feature on the App Store. The data types are not published on a page we could reach. | |
Read 10 September 2026 from the sources listed at the end. Android equivalents run on Health Connect, and the data types available there differ from HealthKit's.
The four questions the matrix answers
Does my food reach the Health app? Six of the eight write nutrition of some kind. What varies is depth: Cronometer sends 13 nutrients out of the 84 it tracks, MyFitnessPal sends calories and some nutrients while explicitly excluding caffeine and vitamin A, and MacroLog sends calories, three macros and 12 micronutrients. If your reason for syncing is to feed a doctor's app or a research study, ask which nutrients, not whether.
Can food come back the other way? Mostly no. MyFitnessPal states plainly that food does not sync from Apple Health into MyFitnessPal. MacroFactor does import daily calories and macros, but they land on its Nutrition page rather than becoming editable meals, and MacroFactor's own rule is that anything you typed in the app beats anything synced in. Nutrition import is a summary, not a diary transfer, and it is not a migration path between apps.
Does my weight stay in step? Weight is the one field almost everyone treats as two-way. MyFitnessPal, MacroFactor and MacroLog all read and write it, so a smart scale that writes to Apple Health updates your tracker without you touching anything.
What happens to exercise? This is where budgets silently break. MyFitnessPal imports exercise only if it was logged the same day, so a workout you record on Tuesday for Monday does not backfill. MacroLog reads steps and active energy and shows them to you, and they never change your calorie budget. That is a deliberate choice: your target already contains an activity assumption, and wearable energy estimates carry error of their own, so letting them top up the target stacks one estimate on another.
How MacroLog's sync behaves
On iOS this is HealthKit; on Android it is Health Connect, and the two platforms do not offer the same data types, so the app writes nutrition differently on each. Written out: calories, protein, carbs, fat, the 12 micronutrients MacroLog tracks, water and weight. Read in: weight, which is two-way, plus steps and active energy, which are informational.
Two rules govern the edges. Nutrients MacroLog has no value for are not written, because a zero in Apple Health is a claim that you ate none of it, and an unknown is not that. And nothing in Health changes your calorie goal; if your step count genuinely doubles for a month, you change the goal yourself, and the TDEE calculator is there for that.
Where this stops working
Sync is not backup and it is not migration. Apple Health holds daily summaries, not your meal-by-meal diary, so exporting nutrition to Health does not let you rebuild a food log in another app. Permissions are per data type and set by you at connection time, so an app that supports fifteen types will still sync nothing if you granted nothing. Historical data usually does not backfill: MyFitnessPal's help centre states that only data logged after the connection transfers in.
MacroLog's own limits belong here too. There is no web app, and multi-device sync is planned rather than shipped, so Apple Health is not a way to get your MacroLog diary onto a second device. AI photo and voice logging need a network; the rest of the app logs offline into a local database first. And nothing about writing to Apple Health improves the accuracy of what you logged. A wrong entry syncs perfectly.
Common questions
Does Cronometer sync with Apple Health?
Yes, both ways. Out: general activity, 13 nutrients, blood glucose, body fat, body temperature, blood pressure, dietary cholesterol and height. In: activity, exercise, height, sleep duration and stages, heart rate, body fat, blood pressure, blood glucose, weight and waist circumference. Connecting is done from the mobile app.
Which tracker sends the most nutrients to Apple Health?
Of the eight here, MacroLog publishes the longest nutrition export list: calories, three macros and 12 micronutrients. Cronometer tracks far more nutrients internally, up to 84, but exports 13 of them.
Will my Apple Watch calories increase my food budget?
In MacroLog, no, by design. Other apps differ, and Noom's support page notes that dietary and active energy permissions exist but can duplicate data inside the app.
Can I use Apple Health to move from MyFitnessPal to another app?
No. MyFitnessPal writes summaries out and reads no food back, and no app here rebuilds a diary from Health summaries. Use the app's own export instead, which on MyFitnessPal is a Premium feature.
What this is based on
- Cronometer: Apple Health integration, read 10 September 2026. Source for both Cronometer lists.
- MyFitnessPal help centre: Apple Health, read 10 September 2026 through Google's index, because the help centre refuses automated requests. Source for the food, exercise, weight and sleep behaviour, the caffeine and vitamin A exclusions, and the no-backfill rule.
- MacroFactor help centre: where nutrition is synced and MacroFactor release notes, March 2022, read 10 September 2026.
- Lifesum helpdesk: connect and sync with Apple Health, read 10 September 2026. Source for both Lifesum lists.
- Noom support: connecting devices and syncing data (iOS), read 10 September 2026.
- Cal AI FAQ, read 10 September 2026. Source for the connection step and for the absence of a published data-type list.
- Lose It! on the US App Store, read 10 September 2026. Source for "Fitness App Syncs" being a Premium feature.
- MacroLog's own health-sync documentation, for the MacroLog row and section.
Next step
If sync depth is what you are choosing on, the head-to-head pages carry the price and feature deltas that sit behind these rows: Cronometer vs MyFitnessPal and MacroFactor vs MyFitnessPal.