You might not be losing weight but, your wallet might become light weight - “Fitness Balance app” and “Calories Tracker app” appears to trick unsuspecting users into approving payments of over US $100.

Upon start-up of the apps, users are requested to scan their fingerprint in order to “view their personalized calorie tracker and diet recommendations.”

However, quick as a flash the app pops-up an in-app payment dialog asking for you to approve a payment of US $99, US $119.99, €139.99

https://www.grahamcluley.com/fitness-tracking-apps-caught-misusing-touch-id-to-steal-money-from-iphone-users/