Reports often circulate about the pros and cons of taking birth control pills — weight gain, weight loss, increased chances of breast cancer, decreased chances of endometrial cancers — but a recent study revealed a little-known side effect that hasn’t been researched until now.
At a recent conference of the American Physiological Society, a study detailing the effect of contraceptive pills on muscle mass was introduced. Researchers found that women taking an oral contraceptive who performed 10 weeks of resistance training gained 40 percent less muscle mass than women who were not taking oral contraceptives.
Exercise physiologist Chang Woock Lee, along with several other researchers at Texas A&M University, attributes this to the way that oral contraceptives affect a woman’s hormone levels. Lee also found that certain pills made muscle gain less likely, such as medium and high androgenic progestins, whose users achieved less than .5 percent gain during the study.
The study focused mainly on lean muscle gain and found that muscle mass increased in both the legs and arms at nearly the same rate for all women regardless of contraceptive use.
Another researcher in the study, Dr. Mark Newman from the University of Pittsburg, explained how they looked at the effects of certain contraceptives on hormone levels.
"In the blood concentrations of women in the study who were taking oral contraceptives, we found lower levels of anabolic or muscle building hormones and higher levels of catabolic or muscle breaking hormones as opposed to women who were not taking oral contraceptives," he said.
So if you’re a birth control user who has been hitting the gym in hopes of increasing your muscle mass and haven’t been successful, this study may offer some insight into why your regimen isn’t working. And if gaining muscle is a top priority on your list, it’s probably time to make an appointment with your doctor to discuss oral contraceptives with lower levels of androgenic progestins or non-oral contraceptives.