Do you think that hormonal birth control makes it impossible to maintain a healthy bodyweight? The article very clearly points to an increase in daily caloric intake.
Those two claims aren't incompatible. If birth control pills increased appetite, people would gain weight on them VIA an increase in daily caloric intake.
(A third option is that being fatter makes people hungrier, so fatter people eat more...but starting down the path of getting fatter might have any random cause at all - that people are eating more doesn't give us much insight into why.)
