Here is how they are promoting this "study" on their site for teens,
http://www.teenwire.com/
Pill Doesn't Pack on Pounds
by Jon Platner
Good news! A recent study disproves what many teenage girls have believed for a long time - that taking birth control pills will make them gain weight. The study followed 66 white girls from age 12. By age 21 more than half of the girls were on the Pill, while the others were not. The researchers found that average weight gain of the Pill users was similar to their peers who weren't on the Pill.
The number one reason that women stop taking the Pill is that they think it's making them gain weight. This study dismisses the myth once and for all, though it's possible that results could vary according to ethnicity, obesity, and exercise habits, since the study was conducted only on healthy white females.