REPOST: Oral Contraceptives and Weight Gain, Myths and Truths and Anecdotes

Jul 06 2011 Published by under Physiology/Pharmacology

And lions and tigers and bears!

Sci is reposting this one in particular because I keep seeing it come up. Again and again I read articles on how combined hormonal contraceptives don't cause weight gain. And again and again I see women posting everywhere on the internet not to trust those dang scientists! I gained weight! And so did my friend!

So I'm reposting this one. Because while I'm sure you may have gained weight, you are an anecdote. And so is your friend. No offense.

@noahwg linked an article (or a blog post? It seems more like a blog post) in the NY Times today, on oral contraceptives and weight gain. The post covers a review of various clinical trials (there are only three listed, but that's because they are using the most stringent measures of three treatment trials per study) and concludes that there is no causal association between oral contraceptive use and weight gain.

Yup. Again. Because this isn't news. In fact, it's a reprint of a review released in 2008. Combined oral contraceptives don't cause weight gain in any of the studies in which they've been tested.

I've seen studies like this before, and I commented on it to a female friend of mine. And I got the response I have now come to expect: "Well, I gained weight!"

Sci's gonna have to put on her ranty pants for a minute.

(Someone needs to make these. I would pay good money for these. Source)

CORRELATION IS NOT CAUSATION. There are many reasons why one might gain weight about the time that one starts taking hormonal contraceptives. Examples of this include: moving off to college, beginning a different style of life, or simply growing older (aging is very correlated with weight gain, and I'm not talking getting up there in your 80's, I'm talking getting older than 12). There are many other reasons why a person starting on hormonal birth control might gain weight.

Why do people always blame the birth control?

My hypothesis is that the aura of hormonal contraceptives is to blame. The idea of putting outside hormones into your body is a scary one, and it's something that people feel they would notice. This may mean that women taking hormonal contraceptives are more on the lookout for changes in their bodies, and thus might notice (and attribute) weight that they gained at that time with the drugs they are taking. And there ARE side effects of hormonal contraceptives. Side effects on mood for some people, on headaches (either reduction or increase), or PMS symptoms (increase or decrease), on libido. Side effects on skin. Just not on WEIGHT.

It occurred to me today that, in this way, oral contraceptives have a thought process around them that is similar to stuff I've seen with things like homeopathy or vaccines and autism. No matter how many studies come out showing that homeopathy doesn't work/vaccines don't cause autism/hormonal contraceptives don't cause weight gain, the myth still perpetuates, and in fact seems to grow. The more studies the are announced about hormonal contraceptives having nothing to do with weight gain, the more people come out of the woodwork saying "But I gained weight! That study must be wrong!"

You may have gained weight. But (1) do you KNOW it was the contraceptive? Correlation is not causation. (2) You are an anecdote. And so are all your friends. You are not a controlled study evaluating the effects of hormonal contraceptives on weight gain. This doesn't mean you didn't gain weight, perhaps you did. It doesn't mean you didn't experience side effects from the hormonal contraceptive. Many people do. It just means that, on average, hormonal birth control alone does NOT cause weight gain.

In case you want references, here are some.

  1. Let's start with animals. No effect on weight or metabolic aspects in rats (these particular rats were rats with diabetes, but it confirms previous findings).
  2. No effect on weight in monkeys of normal weight, but this study actually saw a DECREASE in weight and fat composition in obese monkeys.

Now onward to humans.

  1. The most recent reprint of a 2008 review looking at three double-blinded clinical trials saw no differences in weight, and even looked at people who quit the studies, citing that they gained weight. Numbers of people quitting the study citing weight gain didn't differ between groups either, meaning that the numbers of people who thought they were gaining weight because of the contraceptive were as likely to be on placebo as not. They did see weight gain the progesterone only group getting the contraceptive as an injection. This study included the ring and the patch.
  2. People on combined oral contraceptives in this study gained less weight than those on placebo, and also gained less weight than those who discontinued usage.
  3. Oral contraceptives were associated with LESS weight gain and less fat than placebo in female distance runners.
  4. Another study looking at injectable progesterone vs oral contraceptives found that the oral contraceptive condition had no weight gain, though they did see weight gain with the injectable.
  5. Another study also found reduced fat mass for oral contraceptive users, with NO CHANGE in weight gain.

What can we conclude from this? We can conclude that combined hormonal contraceptives when given orally or as a patch or in the ring cause NO WEIGHT GAIN. What DOES cause weight gain is the progesterone only contraceptive, given as an injectable or as an IUD. Keep in mind, though, that the progesterone only contraceptive is actually not very common, the vast majority of women are on a combined hormonal contraceptive, usually oral, though patch and ring are gaining in popularity.

The other thing you can conclude from this? Weight gain happens. The oral contraceptive conditions in all the studies listed above (humans and animals) DID SHOW weight gain. But that's because EVERYONE showed weight gain. The people on oral contraceptives gained as much weight (or sometimes a little less) as those on placebos. So yes, you might gain weight when you go on an oral contraceptive. But so does everyone, including people NOT on the contraceptive.

To conclude: I believe you when you say you gained weight when you started on a hormonal contraceptive. But was it the contraceptive itself that was to blame? Probably not.

References (Lots of them! And these are only the ones I used. There are more.)

Uras R, Orrù M, Etzi R, Peppi G, Marotto MF, Pilloni M, Zedda P, Lello S, Melis GB, & Paoletti AM (2009). Evidence that in healthy young women, a six-cycle treatment with oral contraceptive containing 30 mcg of ethinylestradiol plus 2 mg of chlormadinone acetate reduces fat mass. Contraception, 79 (2), 117-21 PMID: 19135568

Berenson AB, & Rahman M (2009). Changes in weight, total fat, percent body fat, and central-to-peripheral fat ratio associated with injectable and oral contraceptive use. American journal of obstetrics and gynecology, 200 (3), 3290-8 PMID: 19254592

Beksinska ME, Smit JA, Kleinschmidt I, Milford C, & Farley TM (2010). Prospective study of weight change in new adolescent users of DMPA, NET-EN, COCs, nonusers and discontinuers of hormonal contraception. Contraception, 81 (1), 30-4 PMID: 20004270

Edelman, A., Jensen, J., Bulechowsky, M., & Cameron, J. (2010). Combined oral contraceptives and body weight: do oral contraceptives cause weight gain? A primate model Human Reproduction, 26 (2), 330-336 DOI: 10.1093/humrep/deq335

Adeghate E (2000). Effect of oral contraceptive steroid hormones on metabolic parameters of streptozotocin-induced diabetic rat. Contraception, 62 (6), 327-9 PMID: 11239621

Göretzlehner G, Waldmann-Rex S, & Schramm GA (2011). Extended Cycles with the Combined Oral Contraceptive Chlormadinone Acetate 2 mg/Ethinylestradiol 0.03 mg: Pooled Analysis of Data from Three Large-Scale, Non-Interventional, Observational Studies. Clinical drug investigation PMID: 21250761

Teepker M, Peters M, Kundermann B, Vedder H, Schepelmann K, & Lautenbacher S (2011). The effects of oral contraceptives on detection and pain thresholds as well as headache intensity during menstrual cycle in migraine. Headache, 51 (1), 92-104 PMID: 20946429

Breech LL, & Braverman PK (2010). Safety, efficacy, actions, and patient acceptability of drospirenone/ethinyl estradiol contraceptive pills in the treatment of premenstrual dysphoric disorder. International journal of women's health, 1, 85-95 PMID: 21072278

PROCTER-GRAY, E., COBB, K., CRAWFORD, S., BACHRACH, L., CHIRRA, A., SOWERS, M., GREENDALE, G., NIEVES, J., KENT, K., & KELSEY, J. (2008). Effect of Oral Contraceptives on Weight and Body Composition in Young Female Runners Medicine & Science in Sports & Exercise, 40 (7), 1205-1212 DOI: 10.1249/MSS.0b013e31816a0df6

Gallo MF, Lopez LM, Grimes DA, Schulz KF, & Helmerhorst FM (2008). Combination contraceptives: effects on weight. Cochrane database of systematic reviews (Online) (4) PMID: 18843652

22 responses so far

  • Susan says:

    I was not aware about this. Thanks for writing this article.
    My best regards,
    Susan, creator of como quitar la celulitis de las piernas y gluteos.

  • wriggles says:

    "My hypothesis is that the aura of hormonal contraceptives is to blame. The idea of putting outside hormones into your body is a scary one, and it's something that people feel they would notice."

    You forgot obesity experts who go on about fat being "oestrogenic".

  • FiSH says:

    Sci, thanks for writing about this issue - not the mistaken relationship between weight gain and oral contraceptives per se, but the more general, and more important, issue of mistaking correlation for causality. I find it rather strange that humans are so bad at this. You would think that there would be some massive evolutionary advantage to actually understanding what causes things to happen, yet there are so many instances where humans just totally fail to understand the nature of causation - and then when you point out to them that they are ignorant, they adamantly refuse to care and prefer to remain in their ignorant, blissful surety. I think that this problem is at the core of our failure to teach science in the US (and perhaps elsewhere) - scientific modes of thinking seem to require a fundamental change in cognitive processing that does not necessarily come naturally, but must be acquired - I find it all rather frightening actually. Anyway, I'm going to add this blog to the list of your others that I'm going to have my students read next semester - I cannot possibly hammer in this idea enough.

  • n says:

    I have taken COCPs five separate times in my life, and each time I gained weight when I began taking them, and each time I lost weight when I stopped taking them.

    I think it is really not as simple as "COCPs don't cause weight gain." Sometimes they do. This might be due to:

    (1) Some kind of individual difference that hasn't been considered in these studies (genes, HPA axis activity, who knows). If some women gain weight, some women stay the same, and some women lose weight, this LOOKS an awful lot like "the pill doesn't cause weight gain!"

    (2) Different formulations of the pill. While every pill marketed in the US uses ethinyl estradiol, the doses are different, AND different progestins are used. Some studies (see here: see differential effects depending on the generation of progestin the pill uses.

  • n says:

    One more comment -- I haven't been through all the studies you listed, but I seem to recall that in the Edelman et al. (monkey) paper, food intake was controlled to maintain the animals' body weight. This strikes me as perhaps a tiny bit of a confound.

  • Adrian Blake says:

    When I was with my ex, she went on the pill and then I put on weight. Where's your fancy science to explain that one huh? HUH?

  • FiSH says:

    n, as Sci says, you are still just an anecdote, even though your weight gain/loss seems time-locked to starting/stopping the pill. The science says that there is, on average, no evidence for weight gain in response to oral constraceptives. Nonetheless, your point is well taken - that there may be a subset of the total (not enough to produce an overall significant effect in clinical trials) that do show such a change. This is a general problem with clinical trials (and even preclinical trials in animal models), that there may be subsets of people that repond differently, but without looking you'll never know - it is problematic both for identifying rare, but potentially dangerous or even not-so-dangerous, side effects and for proving efficacy (the drug may work great for some people but not others, but the overall effect is not significant when you average those groups together). This is not the way that people want to think about this (especially the aspiring pharmaceutical start-up that wants a billion-dollar drug). They want it to be simple. But it's not. So saying, in this case the argument appears to be much stronger for individuals, who give rise to anecdotes, making mistaken attributions of casaulity, than for individual variation in the effect of oral contraceptives on weight gain.

  • n says:

    My point is not that there may be some tiny subset of freakos who gain weight; my point is that if an equal number of people gain and lose weight (note some of the studies above *did* find effects of weight loss), no matter what the effect size or what the n, we will never detect this effect.

    That does not mean it does not exist.

    Weight gain is tied with mood changes as the third most common reason women discontinue taking oral contraception (, after spotting and nausea. That's an awful lotta anecdotes, right there. Seems like there must be some reason all of these women are experiencing the same side effect -- like, maybe it's not all in their heads.

  • FiSH says:

    N, actually your reasoning is wrong in a couple respects. Statistically, even if half the women gained weight and half did not, it would likely be signitificant overall (unless half actually lost weight which has not been suggested either anecdotally or by scientific study). The only possibility is that it is a relatively small percentage of women gain weight and that this effect is overwhelmed by the non-effect in the majority of individuals. I don't mean to belittle this circumstance for those women for which this actually occurs, but it is still most likely that the majority of individuals that attribute weight gain to the drug do so out of mistaken causality. People believe in, and attibute casaulity to, lots of things that aren't true. There was a great study (by Dorothy Einon I believe) back in the 70s looking at PMS symptoms. When women thought they were on a PMS study they attributed a number of symptoms to PMS, but when they thought they were on a cancer study they did not. This is the whole reason that anecdotal reasoning is problematic, and I think the more important point in Sci's post.

  • n says:

    Please re-read my post. My reasoning is not wrong; I described the exact situation you put forth -- equal numbers of women losing and gaining. The potential for weight loss is indeed supported anecdotally, and by scientific evidence, including one study that was linked in this post.

  • Joan says:

    Sci, thanks for writing this article. This is easily one of the most useful articles I've read this year. I was not aware about this.
    My best regards,
    Joan, creator of Como vender en internet.

  • SN says:

    Sci, I'm not sure about your comment about progesterone-only methods. I had been told by an obgyn that the hormonal IUD does not cause weight gain, so I did a search. (And, because I can't help but throw in my useless anecdotal evidence: I have a hormonal IUD and haven't gained an ounce.) According to a recently published study of studies, even progesterone-only methods only have been demonstrated to have a small effect on weight gain, and this is even smaller for IUD's. So, I wouldn't be so quick to cast the weight gain blame on progesterone-only methods. Just a thought!

    Here is the pubmed link:

  • [...] 50 BILLIONTH TIME. Birth control pills (the estrogen and estrogen/progesterone combination pills). Do. Not. Make. You. [...]

  • "Say, you got a nice blog article.Really thank you! Really Cool."

  • pg says:

    n - you're wrong. What you'd see in that case wouldn't be a lack of any change but you'd see two overlapping bell curves. Researchers don't just look at the median value, they analyze the data to see how those values are obtained. If there were a subset of people who gained additional weight due to the pill and a corresponding subset of people who lost weight then we'd see a few things compared to the placebo - a greater spread, a lower coefficient of correlation, multiple peaks of data, etc.

  • Monika aggarwal says:

    i didn't aware about this, thanks to u share with us this article.

  • weight gain says:

    One can lose weight by taking smaller doses as well along with progestins that are different to testerone. Substances that don’t contain desogestrel, norgestimate, or drospirenone usually don’t stimulate the sense of hunger.

  • Health says:

    Im getting off mine too. Weight gain has been consistent and no matter how much I exercise or eat right (and I eat little to no carbs and eat mostly lean meats and whole fruits and veggies), the weight continues to gain. At this point my birth control is the only explanation. Ive been on it for the past 12 years and will miss the benefits but this weight issue is out of control.

  • mannie says:

    I haven't been able to solve my problem with weight. This morning, that I broke, 2 teeth might hold a solution to the problem. No eating, no weight gain.

  • Mellisa says:

    Can you please assist, last year December 2013 I started taking birth control pills (Trigestral) and now am on my third pack which I opened friday 31 Jan 2014.

    Most people say they experience weight gain while on birth control but in my case its completely the opposite, I have lost weight tremendously and am not happy about it.

    When I read the leaflet which comes with the pill pack it says that some of the side effects includes Weight gain or loss (and I have experienced loss of weight which am not happy about)

    All I need to know is will this bad side effect fade and how long will it take for it to fade and will I get back on my normal body weight, am normally a size 30 and now am like a 26 -28.

    Also opened a topic here:

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