Birth Control Pills
Related: 6 IUD Myths — Busted!
"Studies comparing large groups of women who take and do not take birth control have shown no difference in weight gain," gynecologist Richard K. Krauss, MD, told Shape. This brings us back to where we started — you can and should choose your preferred method of birth control however you see fit.
As Bedsider notes, the relationship between the pill and weight gain is complex; it's true that large studies show that there's no direct link between the pill and weight gain overall, but that's not to say that individual variations are impossible.
This means that the best advice is to choose the method that makes the most sense for you and your lifestyle.
Still, knowing that weight change is at best a very unlikely side effect can keep you from prematurely ruling out options that may work really well for you.