By Thaddeus M. Baklinski

NEW ORLEANS, April 23, 2009 ( – A new study presented at the annual meeting of the American Physiological Society in New Orleans found that women who use the contraceptive pill gain far less lean muscle mass from weight training compared to those who don’t take oral contraceptives.

The study, led by Chang-Woock Lee and Steven Riechman from the Department of Health and Kinesiology at Texas A&M University in College Station, and Mark Newman of the Human Energy Research Laboratory at the University of Pittsburgh, found that oral contraceptive use limits muscle gain from strength training in women under 35.

The researchers studied 73 generally healthy women between 18 and 31 who completed a whole-body resistance exercise training program consisting of 13 exercises performed three times per week for 10 weeks. Of these, 34 took the pill and 39 did not. Both groups were encouraged to eat at least half a gram of protein per pound of body weight each day – about a third more than recommended by U.S. nutritional guidelines – to ensure they got enough protein and calories to build muscle.

Lead researcher Chang Woock Lee said there were significant differences in muscle growth between the two groups. Lean muscle mass increased by just 2.1 percent in the oral contraceptive (OC) users, compared to 3.5 percent growth in non-OC users.

“We were surprised at the magnitude of differences in muscle gains between the two groups, with the non-OC women gaining more than 60 percent greater muscle mass than their OC counterpart,” the researcher stated.

Blood samples taken before and after the training period showed that OC users had significantly lower levels of muscle-building hormones such as testosterone and far higher levels of muscle-breaking hormones such as cortisol.

Elevated cortisol levels have been linked with the onset of most diseases, increased cholesterol levels, aging skin, graying hair, mental and emotional fatigue, diabetes, and accumulation of excess body fat, a common occurrence in women in the “pill.”

Lee said these findings “could help explain” why OC users showed diminished muscle gains from resistance exercise training, but that “vigorous future studies with more stringent control and clever design will be definitely needed to confirm the results and/or elucidate the underlying mechanism conclusively.”

“The factors that explain the differences in the magnitude of the responses to resistance exercise training between individuals are largely unknown,” Lee said.

“Numerous health and performance benefits including improved exercise/athletic performance, body composition, esthetic beauty, and self-image can be attained from the increased muscle mass and strength associated with resistance exercise training. OC users may not be able to fully enjoy those benefits while experiencing impaired exercise performance and difficulties achieving athletic goals due to diminished muscle responses they get from resistance exercise training,” the researchers concluded.