No, but the auth token might have. Pretty sure facebook would have preemptively invalidated them all, but if not, you should login to your facebook account and unlink MyFitnessPal.
MyFitnessPal never had your Facebook password, so there's no way for it to be stolen by a breach.
They would have had a long lived token though
How would you even think this would happen?
Maybe because I don’t typically work with authentication software? I feel like that’s not a hard conclusion to reach, don’t understand the incredulous response...