For many, hormonal contraceptives are the most convenient form of birth control. However, the fear of weight gain can be one of the most dreaded aspects of starting it and a reason why a lot of people will stop using it.
Weight gain is a really common concern for many people who are wishing to start hormonal forms of contraception and stories from others who’ve gained weight can be enough to deter you from trying it. However, what does the evidence really say about hormonal contraception causing weight gain?
What is hormonal contraception?
Hormonal contraception contains either or both artificial progesterone and artificial oestrogen.
Combined hormonal contraceptives include the birth control pill (also sometimes just called “the pill”), contraceptive skin patches and contraceptive vaginal rings. They are called combined contraceptives because they include artificial forms or progesterone and oestrogen. Some hormonal contraceptives, such as the “mini pill” and the hormone-releasing contraceptive coil, contain only artificial progesterone (1).
You might not be on hormonal contraception for birth control. It has a number of other uses including the treatment of acne and treating or reducing symptoms of PCOS, endometriosis and heavy, irregular, or painful periods (2–4).
What does the evidence say?
Weight gain when taking the combined contraception is a difficult area to research.
This is because in order to find out whether hormonal contraception causes weight gain, there needs to be studies with one group of women who use hormonal contraceptives over a long period of time and another group who do not. The groups can then be compared to see if there are any differences in weight. Hormonal contraceptives are so reliable, not many women are willing to use contraceptives that could be less effective or may even be placebos and not work at all in order for these studies to be carried out.
Researchers from the Cochrane Collaboration looked for high-quality studies on hormonal contraceptives in which weight was recorded. They were only able to find a few studies that compared hormonal contraceptives with “fake” hormonal contraceptives (placebos) and measured the impact on weight (5).
However, these studies did not have enough participants and were not well-designed to be able to provide a definite answer. In addition, most of the studies didn’t record the participants’ weight very accurately and sometimes only the number of women who reported that they stopped taking the pill because of weight gain was recorded.
It’s not possible to say for sure whether the participants who used hormonal contraceptives gained more weight than the women in the other group.
Association or causation?
It’s confusing when the published evidence is telling you hormonal contraception does not cause weight gain but a lot of people taking the pill will report gaining a few pounds in the weeks and months after they start it.
We know that taking the hormonal contraception is associated with weight gain but that doesn’t necessarily mean it is caused by using it.
This may seem complicated but let’s try and explain it in a different context. If you’re studying for an exam there will be an association between the increasing hours people studied for and achieving a higher score. This makes sense, the more you study the higher mark you will achieve (for the majority of people).
However, that doesn’t mean studying for more hours caused an individual to achieve a higher score because you will have people who studied for 2 hours achieve the same score as somebody who studied for 6 hours. Many factors will have influenced a person’s exam score such as IQ, their motivation to score highly, their study environment or how much sleep they got; it’s hard to know for sure which factor caused the high score.
This is the same for women taking hormonal contraception, there will be many other factors influencing weight gain such as body habitus, genetics, education, income, ethnicity and where you live. When scientists do research on weight gain and hormonal contraception these are the questions they ask, did the pill cause the weight gain or was it because of other factors?
What is causing my weight gain when taking hormonal contraception?
When we bring it down to basics, people gain weight because of the following reasons:-
- Fluid retention
- An increase in muscle tissue
- An increase in body fat
Theoretically, hormonal contraceptives could contribute to weight gain if the action of the hormones in your body leads to fluid retention and increasing body fat. We know that artificial progesterone’s can induce water retention (6) and artificial oestrogen has been associated with increased subcutaneous fat, especially in the breasts, hips, and thighs (7). However, it’s not that easy to say whether that’s true because women who don’t use hormonal contraceptives also gain weight as they age.
It seems very unlikely that hormonal contraceptives cause major weight gain. If there were a strong effect, we would expect it to be noticed in the evidence being published.
However, this doesn’t rule out the possibility that individual women could gain weight that is caused by taking hormonal contraception; this is why it is listed as a side effect on the packaging of most hormonal contraception you will take.
It’s important to remember that when looking at the evidence, the numbers are averages. Some people in the studies will gain weight and some lose weight, and the amount of weight differs from person-to-person. We need more research to fully understand how and why different types of birth control may contribute to weight gain in some people, but not others.
When it comes to contraception, you have many options to choose from; I’ve written more on pills, long-acting options and sterilisation. If you’re finding any of the side effects, including weight gain, difficult it’s always worth discussing this with your GP or sexual health clinic to consider other options.
The beauty about contraception is that if you don’t like the first method you try, there will always be other methods to consider that may make you feel comfortable and that suit your lifestyle.
References
1. FSRH. FSRH Clinical Guideline: Combined Hormonal Contraception. Fsrh. 2020;2019(January 2019).