To change the email address of your Account, follow these steps:

1. Open the Withings App.
2. Tap the Profile icon.
3. Tap the Settings gear icon in the top right corner.
4. Tap Account & Security.
5. Tap Change my e-mail under "Account Settings".
6. Enter the new email address twice to confirm.
7. Tap Update my e-mail to finalize the changes.
8. You will receive a confirmation email on the new email address to validate the change. 
   Note: The link is valid for 1 hour.
9. Click Validate.
10. You will be redirected to a web page informing you that the new address is validated. Your previous email inbox will also receive a confirmation email. 

Note: You can only change your email address if you log in using your email and password; it won't work using Google Sign-in or Apple ID, as the option won't appear.