Do Birth Control Pills Make You Weaker? An Answer, According to Science

If you’re a woman, you’ve probably thought about taking or have taken some kind of birth control. 

One of the most popular birth control methods is hormonal contraception, also known as “the pill.” 

For example, a recent study found that about half of the 430 female athletes surveyed had used hormonal contraception, with about 70% taking oral birth control pills.

We don’t need to get into the nitty-gritty details, but essentially what these pills do is short-circuit women’s hormones in a way that causes them to become infertile. 

As you probably know, though, birth control isn’t without side effects. Many women experience weight gain, spotting or irregular bleeding, migraines, disrupted sleep, and high blood pressure. 

What’s more, many women report that birth control pills reduce their athletic performance. 

If, like these women, you’re a gal who likes to lift weights, play sports, run, cycle, or do any other kind of cardio, you might be wondering what affect tampering with your hormones has on your workouts. 

That’s exactly what a team of scientists at Nottingham Trent University wanted to find out in a recent study.

Let’s look at what they did.

Table of Contents

• What Did the Researchers Do?
• What Were the Study Results?
• What Does This Mean for You?
• The Bottom Line on Birth Control Pills and Athletic Performance

What Did the Researchers Do?

Over the years, many studies have looked at how birth control pills affect athletic performance.

Some studies show that taking birth control pills causes performance to wane, while others show it has little effect.

With all of these different results, the researchers at Nottingham Trent University decided to take a step back, look at all of the data on this topic, and use a variety of statistical models to decipher which way the body of evidence seemed to be pointing.

Read: How to Think About Science 

This kind of study is known as a meta-analysis, because it looks at a problem from a “meta,” or higher-level perspective. More specifically, a meta-analysis is a study of a bunch of other studies about a particular topic.  

The main benefit of a meta-analysis is that by lumping together the results of multiple studies, you can spot trends that might otherwise be obscured in different studies on small groups of people.

Before we look at exactly how the researchers conducted their study, though, it’s helpful to understand how the menstrual cycle works. 

Read: The Complete Guide to Eating and Training During Your Menstrual Cycle

The menstrual cycle refers to a series of hormonal and physiological changes that occur in a woman’s body roughly every 28 days to prepare her for pregnancy.

The menstrual cycle begins with menses or menstruation—the bleeding that occurs as the uterine lining leaves the body, more commonly referred to as the “period.”

A period typically lasts three to five days, though it can be shorter or longer, and marks the beginning of the first phase of the menstrual cycle: the follicular phase.

The follicular phase lasts around 14 days in a normal 28-day cycle, and is often divided into an early and late follicular phase, each lasting about 7 days. That is, the early follicular phase comprises roughly days 1 to 7 of the menstrual cycle, and the late follicular phase days 8 to 14.

Around the fourteenth day of the follicular phase, the egg passes from the ovary to the Fallopian tube in a process known as ovulation. 

This marks the end of the follicular phase, the middle of the menstrual cycle, and the beginning of the luteal phase.

Like the follicular phase, the luteal phase is often split into an early and late phase, with each lasting about 7 days. That is, the early luteal phase comprises roughly days 15 to 21 of the menstrual cycle, and the late luteal phase days 22 to 28.

At the end of the luteal phase, menstruation begins, and the cycle starts anew.

So, how do birth control pills fit into all of this? 

First, some background on how the process works.

Birth control pills normally come in packs of 21 or 28 pills.

For women who use packs of 21, pills are taken for 21 days straight. This more or less shuts down the normal fluctuation of hormones that causes menstruation and increases fertility. This is known as the consumption phase.

Then, for the other 7 days of each 28-day cycle, they don’t take any pills. This is known as the withdrawal phase.

For ladies who use packs of 28 pills, the process works the same way. The only difference is that during their withdrawal phase, they continue taking pills. The pills they take during this time are placebo pills that don’t contain any hormones, and are only taken because they help to keep women in the habit of taking a pill every day.

All of these different variables make studying birth control tricky. 

Thus, in this particular study, the researchers decided to do three separate meta-analyses on different groups of people: 

1. A meta-analysis that compared the athletic performance of women during their seven-day withdrawal phase to naturally menstruating women who were not taking birth control during the first seven days of their menstrual cycle. 
2. A meta-analysis that compared the athletic performance of women during their three-week consumption phase to naturally menstruating women during the last three weeks of their menstrual cycle (the mid-follicular phase to the luteal phase).
3. A meta-analysis that compared the athletic performance of women on days they took birth control pills to days they took no pills or placebos.

In all three meta-analyses, the researchers only included studies that used healthy female participants between 18 and 40 years old, included at least one group of participants that already took birth control pills before enrolling in the study or agreed to take birth control pills as part of the study, and measured strength or endurance performance.

Specifically, the studies tested a variety of athletic abilities, such as sprinting, rowing, jumping, grip strength, and leg extension strength. 

The researchers found a total of 42 studies that met these criteria, including a total of 590 participants. The researchers went a step further and measured the quality of each study using a scientific tool known as the Downs and Black Checklist, with 7 studies being graded as high-quality, 21 as medium-quality, 10 as low-quality, and 4 as very low-quality.

To ensure that the low-quality studies didn’t corrupt the results, the researchers also ran a separate analysis where they only looked at the medium- and high-quality studies, then compared the results to when they also included the low-quality studies, to see if anything changed. (If the results turned out to be substantially different after excluding the crappy studies, they could take this into account when interpreting the results).

As a further precaution, the researchers also excluded any results that were obviously outliers (and most likely due to errors in the studies they were examining). 

Summary: The researchers performed three meta-analyses that examined several ways birth control pills might affect performance, and used rigorous methods to ensure the results were accurate.

What Were the Study Results?

The first meta-analysis found that women not taking birth control pills tended to perform slightly better during the first week of the menstrual cycle than women who do take birth control pills, though the difference between the two tended to be insignificant. 

(Remember that for the women taking birth control pills, this would be during their withdrawal phase, so they weren’t actually taking the pills during this time).

The second meta-analysis found women not taking birth control pills tended to perform slightly better during the last three weeks of the menstrual cycle than women taking birth control pills, though again, the difference was insignificant.

(Remember that for the women taking birth control pills, this would be during their consumption phase, when they’re actively taking “the pill” every day).

Finally, the third meta-analysis found that there’s basically no difference in athletic performance between days during the withdrawal phase and the consumption phase among women who take birth control—they didn’t perform any better or worse on days they were taking the pill or days they weren’t taking it. 

Summary: The researchers found that taking birth control pills may slightly reduce your athletic performance, but the effects are probably insignificant for most people.

What Does This Mean for You?

According to the results of this study, gals who don’t take birth control pills probably perform ever-so-slightly better than those who do. Several other well-designed studies not included in these meta-analyses supports this idea, too.

Here’s the weird thing: Although birth control pills probably do reduce athletic performance to some degree, most female athletes still take them. Specifically, around 57% of female athletes take birth control pills, compared to just 12% of the general population.

Why? 

Probably because the negative effects on performance tend to be small, and some women feel they’re outweighed by the upsides of birth control.

Upsides, you wonder?

Although birth control pills are generally taken to control pregnancy, they also can take the edge off of many of the side effects of the menstrual cycle. 

In most cases, birth control pills more or less eliminate the period by ceasing menstruation, which also eliminates many of the symptoms such as hot flashes, fatigue, nausea, digestive upset, and so forth. Thus, if taking birth control pills helps you train harder and more consistently, then it may be a net positive in terms of your athletic performance. 

That said, it’s also worth considering some of the other potential negative effects of birth control pills. Some of the most common side effects include: 

• Headaches
• Increased appetite and weight gain
• High blood pressure
• Increased hair growth
• Breast tenderness
• Disrupted sleep

And of course, if any of these side effects interfere with your training, then they could wipe out the benefits (aside from preventing pregnancy, if you consider that a benefit). 

Thus, it’s worth weighing these factors in the balance before you make a decision about whether or not you should take oral contraceptives (birth control pills), or use some other means of birth control.

Summary: How birth control pills affect your performance is very individual. Some women feel the pros (lack of menstrual cycle side effects) outweigh the cons (birth control side effects), and others don’t.

The Bottom Line on Birth Control Pills and Athletic Performance

The birth control pill is a popular method of contraception, particularly among athletes. Many ladies who exercise, however, worry about whether it’s having a negative effect on their performance.

Three recent meta-analyses from Nottingham Trent University found that women who don’t take birth control pills probably perform better than women who do, though the difference is likely so small it may be imperceptible.

While birth control pills may not have a direct effect on your athletic performance, they could have significant indirect effects.

On the one hand, many female athletes like to take birth control pills because they eliminate many of the unwanted side effects caused by their menstrual cycle. Thus, they don’t need to worry about their period interfering with their workout routine.

On the other hand, many female athletes (and women in general) experience unpleasant side effects from birth control, which can interfere with their training as much or more than their menstrual cycle. 

Thus, whether or not you take birth control pills is a personal choice. 

If you feel they’re a net positive (and you’re trying to avoid pregnancy), they may be worth taking. If you feel they’re a net negative (or you want to get pregnant), it’s best to avoid them.

What’s your take on how birth control pills affect performance? Have anything else to share? Let me know in the comments below!