Here's what the email sent to customers says:
Please accept our sincerest apologies if you can no longer find the MyFitnessPal Windows phone App or are having issues accessing the app. Unfortunately, due to several issues with the app, and not enough demand of the app from our members, we have decided to no longer offer an app on the Windows Phone platform.
Due to limitations of the Windows Phone store, we are unable to provide ongoing access to the app for existing users. Once a member logs out of the app, access to the app will no longer be available.
For members that may still have access to parts of the app, we are also unable to further support triaging of the app. Your account can still be accessed via your mobile web browser, or computer at our main website www myfitnesspal com or via the iOS and Android platform.
I don't believe we've ever featured MyFitnessPal here on AAWP, but I'm sure it's popular in some parts of the world. Comments welcome if this affects you.
Interestingly, we had Microsoft discontinuing its own Health & Fitness application late last year, though I did note at the time that quite a bit of the exercise tracking and calorie burning calculations were available in the new UWP Microsoft Health.