Birth Control May Slow Muscle Development

Birth control pills make it harder for women to gain muscle as they exercise, according to a new study.

The pill is also associated with lower hormone levels, researchers said in a news release.

They study involved 73 women ages 18 to 31 who were put on a 10-week workout plan. About half used oral contraceptives, and half did not. They were also asked to eat enough protein to promote muscle growth.

After the workouts, the women who take the Pill gained about 2.1 percent lean muscle. Those who were not on birth control gained about 3.5 percent. But both groups were similar in strength gains and the size of their arms and legs.

Researchers said they were surprised at how much more effective the weight lifting was for women who do not take oral contraceptives.

They said more research would be needed to determine why they saw that result.

The study was conducted by Chang-Woock Lee and Steven E. Riechman of Texas A&M University and Mark A. Newman of the University of Pittsburgh.