Women who engage in strength training and use birth control pills develop 60% less muscle mass than women who do not take the pill. This is evident from research by Texas A&M University [1].
Less anabolic hormones due to birth control pill
The researchers divided 73 women aged 18-31 into two groups. 34 of them used the pill, the remaining 39 did not. Both groups underwent a 10-week training protocol focused on the whole body.
They trained three times a week, performing 3 sets of 6 to 10 repetitions at an intensity of 75% 1RM (i.e., 75% of the weight with which they can perform one repetition of a specific exercise). This included the chest press, lat pull down, leg extension, triceps extension, arm curl, and abdominal crunch among others.
Results
After ten weeks, the results were compared, measuring body composition (lean mass/fat mass), as well as the anabolic hormones IGF-1 (Insulin-like Growth Factor 1), DHEA (Dehydroepiandrosterone), and DHEAS (Dehydroepiandrosterone sulfate) in the blood. The amount of the stress hormone cortisol was also measured.
The group that used the pill gained an average of 1 kilo of lean mass. The group not on the pill gained an average of over 1.6 kilos of lean mass, thus sixty percent more. However, strength in the various exercises did not differ. The same was true for the circumference of the arms and legs, but the latter could possibly be explained by a decrease in fat compensated by muscle mass.
A reason for this difference can be found in the anabolic (muscle-building) hormones IGF-1, DHEA, and DHEA’s, all of which were present in lower amounts in the blood of the women who were on the pill. For example, DHEA, a precursor to (can be converted into) testosterone and estrogen, was decreased in the group on the pill while it remained the same in the other group. The stress hormone cortisol, which causes muscle breakdown, was actually higher in the group on the pill.
Oral contraceptive use impaired muscle gains in young women which was associated with lower DHEA, DHEAS, and IGF1 and higher cortisol.
Chang Woock Lee, Texas A&M University
The researchers attribute the cause in part to the action of progesterone, which, along with estrogen, makes up the components of the birth control pill. Progesterone binds to receptors for androgenic hormones such as testosterone. Once progesterone has bound to a cell’s receptor, testosterone can no longer do its job in that cell.
Sporting benefits of the pill
For men who are worried about their wife now immediately banning the pill and having to “go rubber”: There are also (sporting) benefits of the pill that may outweigh the disadvantages mentioned in the above research.
Limited blood loss
Blood loss during menstruation is not exactly conducive to sporting performance. As mentioned, the pill partially consists of progesterone. Progesterone is normally found in large amounts only in women. Its production and release are linked to menstruation and possible pregnancy. Progesterone prepares for a potential pregnancy. If pregnancy does not occur, the amount of progesterone falls, eventually leading to menstrual bleeding. The use of (progesterone in) the pill reduces the chance of, among other things, an iron deficiency due to bleeding [2,3,4].
Planning menstruation
When I write an article based on research, this research is often just known and yet to be published. However, the Texas study is already a few years old and has already received some attention. One website concluded with advice to ladies[4]:
…to leave the pill aside before a bodybuilding competition.
This statement makes no sense for various reasons, showing that the author really knows nothing about bodybuilding. You don’t just “train a bit” for a bodybuilding competition. This is a process that takes at least months, or more likely, years. Of course, there may be competition preparation in the last few months. Then, however, you are specifically working on cutting, burning body fat. If you were to forgo the pill for a competition in December, for example, it would make more sense to not use the pill during the months up to (and including) October because you are still in your “bulk phase.”
Naturally, you then try to retain as much muscle mass as possible in those last months, and yes, there is a chance that retaining muscle mass is more difficult if you are on the pill (for the same reasons as in the Texas study). However, the use of the pill also has a major advantage: What if you otherwise have your period on the day of the competition? I don’t need to be a woman to understand that it’s probably not pleasant to be flexing on stage in your bikini. I think no advertisement for sanitary pads with active women can change that.
The ability of the pill to plan menstruation can also be worth a lot in terms of sports.
Conclusion
I have limited myself here to the impact of the pill on muscle mass. However, the pill has many more effects on general health. Consider, for example, the impact on bone strength, about which multiple studies contradict each other. I assume that as a woman you have already delved into this. Most likely, this does not apply to the impact on muscle mass.
With this, I am not trying to say that you should get off the pill. There are always multiple considerations for and against, this is just one of them if you find muscle mass important. In an article from the series: “Sex, beer, weed, and muscles,” I concluded that the benefits of abstinence by men for testosterone levels are not worth it for me. Having no sex for a week or longer to increase testosterone levels, also yielded unclear results. This made it an easy choice for me.
Now, I must say that the shown difference of 60% in muscle mass is very large. Some things you might not even want to know.
References
- Chang Woock Lee, Mark A. Newman, and Steven E. Riechman. Oral Contraceptive Use Impairs Muscle Gains in Young Women. FASEB J.April 2009 23 (Meeting Abstract Supplement) 955.25
- Kim Bennell, Susan White, Kay Crossley. The oral contraceptive pill: a revolution for sportswomen? Br J Sports Med 1999;33:231–238.
- Harvey LJ, Armah CN, Dainty JR, Foxall RJ, John Lewis D, Langford NJ, Fairweather-Tait SJ. Impact of menstrual blood loss and diet on iron deficiency among women in the UK. Br J Nutr. 2005 Oct;94(4):557-64. PubMed PMID: 16197581.
- Barr F, Brabin L, Agbaje S, Buseri F, Ikimalo J, Briggs N. Reducing iron deficiency anaemia due to heavy menstrual blood loss in Nigerian rural adolescents. Public Health Nutr. 1998 Dec;1(4):249-57. PubMed PMID: 10933425.
- npowetenschap.nl/nieuws/artikelen/2009/april/De-pil-slecht-voor-spiermassa.html
