The important point to understand here is that contraceptives have synthetic hormones in them that bind more strongly to certain estrogen and progesterone receptors and more weakly to others.
The research is mixed, but it leans toward oral contraceptives speeding up the metabolism. Now, you might think this would be a good thing, but it typically results in SHMEC going out of check as well. As a result, many women hold more water and also end up having their hunger, energy, and cravings go out of check when they are on birth control. That’s part of why they gain weight. This is not necessarily something that the hormones themselves are doing. The issue is that they can trigger changes in SHMEC.
The good news: By following the program, and keeping your SHMEC in check, you should be able to get the benefits of the oral contraceptive without the negative effects.