He popularized a method of releasing from bad eating habits.
is this correct? I am not sure about the connection "method" with "of"
As StoneyB says, release is a transitive verb and thus it requires a direct object. This could have been correct if you'd have written...
He popularized a method of releasing (someone) from bad eating habits.
But that's not the case.
And hence, you can change the sentence -
He popularized a method of getting rid of bad habits
That's just one of the ways to tell that though.