1. Open the Health app on your iPhone.
2. Tap the profile icon on the top-right, and on the next screen, select Apps, under Privacy.
3. On the Apps page, select Health.
4. Now, if you want to delete all of the data at once, tap on the Delete All Data from Health button.
However, once you tap on Delete All Data from Health, all your data related to that particular app will be deleted at once. And, since the process is irreversible, you cannot retrieve the data back again. So, if you do not wish to delete the entire data related to health, and want to instead get rid of some listings, you can delete each data entry individually, as well.