Whether or not birth control causes weight gain is a topic of gigantic controversy in the health literature. More than 50 percent of women think that it does, and up to 20 percent change their pill or go off of the pill because of this belief (here, here, here, here, here, here, here and here.).

Yet most researchers don’t believe these women!!

Really, they don’t. It is possible that they are right to do so. Most studies indicate there isn’t much of a statistical effect on weight maintenance in the long term at all.

Nonetheless, even if there is not a statisitcal significance for the population as a whole, individual women can and often do suffer from weight gain when on the pill. Whilemany call weight gain a “myth,” I do not. I simply know too much about the biochemical theory and have talked to too many women about their experiences to do so.

My book “Birth Control Unlocked” can help you find a form of birth control that will work best for your body and my book “Weight Loss Unlocked” can help you healthfully bring your weight back into balance.

The means by which weight gain happens, I believe, are multi-fold, and I’ll go through all of them below. First, a quick primer on birth control will get us set up to understand how it all fits together.

How birth control works

Almost all forms of birth control contain hormones. There are a few that do not. Prophylactics such as condoms are obvious exceptions, as are the methods of tubal ligation — getting your “tubes tied” — and the Fertility Awareness Method, which basically helps you chart your fertility cycle so you know when to avoid unprotected sex in order to avoid pregnancy. The final and most popular form of non-hormonal birth control is the copper IUD. The copper IUD is expensive, however, and it comes with risks of copper toxicity as well as side effects of cramping and heavy bleeding.

Most women therefore end up on hormonal birth control. The way that it works is quite simple: the body cannot ovulate if there is progesterone in the bloodstream. Therefore, all hormonal birth control options contain some form of synthetic progesterone. Some of them have estrogen added into the mix because some women need it in order to achieve the best possible hormone balance. These options are most popular in pill form, but can they also be found in the form of a patch, an injection, an implant, a vaginal insert, or an IUD.

Why weight gain is not quite as much of a problem as it used to be

Back when the birth control pill was first invented in the 1960s, there was nearly 1000 times as much progesterone and estrogen in the pills as there are now. This is an extraordinary comparison. Back then, all of the side effects including weight gain were much more severe and much more common, simply because the amount of hormones were that much higher.

Moreover, many women today experience a “normalization” after starting on the pill. There may be an initial period of weight gain, but after three months of use the symptoms lessen. Biochemically, this makes some sense, as the pituitary gland learns to accomodate the exogenous hormones.

Finally, as I stated before, even though most women think birth control causes weight gain, statistically, it doesn’t really seem to. Meta-analyses of dozens of investigations have concluded that hormonal birth control does not significantly affect body weight or composition, at least not without statistical significance (here).

Why weight gain is still a concern today

Even while most women do not experience weight gain while on the pill – and especially if they find the “right fit” for them – some still do. Moreover, certain formulations of birth control may be more antagonistic to maintaining a healthy weight than others. For example, in one study, Depo-Provera users gained ten pounds on average over the course of 18 months.

So far as I can tell, there are three ways exogenous (exo = “from the outside”) hormones can influence your weight:

1) By increasing appetite,

2) By causing water retention, and

3) By increasing the rate of fat deposition

What does science have to say about each of these categories?

1) Appetite increase

Contrary to what you might otherwise guess – and to that which is broadly opined on the internet – estrogen is an appetite suppressant.  How is not totally understood, though it is widely thought that estrogen spontaneously decreases calorie intake by increasing the potency of the satiating actions of some gut peptides, especially cholecystokinin. The more cholescytokinin produced by the gut, the more full the brain feels. Moreover, estradiol stimulates anorexigenic (stop eating) POMC/CART activity and inhibits orexigenic (keep eating) NPY/AgRP neurons.

Estrogen appears to boost all of of these things, in both rodents and humans. Rats that have had their ovaries removed, for example, spontaneously eat more and gain weight. When injected with estradiol, their normal feeding and weight behaviors are restored.

Progesterone on the other hand appears to stimulate appetite. This is the case with rodents as well as with humans. First it blocks estrogen’s satiating effects, since estrogen and progesterone often act as counter-balances to the body. It also stimulates appetite all its own.  This could be why you want ALL THE DESSERT as it gets close to your period.

For the record, testosterone increases appetite, too – which is relevant for women who have PCOS or elevated testosterone levels. It also tends to promote fat storage in the abdomen rather than in “female fat” areas like the hips and thighs. Minimizing testosterone levels by minimizing stress and overcoming insulin resistance is a great way to help lose weight and regulate food cravings.

Hirschberg, 2012. Click to zoom.

2) Water retention

Formulations of the pill that have high quantities of estrogen and progesterone or that are especially high in estrogen may cause water retention.

Estrogen causes tissues to reabsorb sodium, which increases sodium levels in the body’s fluids. Elevated sodium causes water weight, because the body balances the extra sodium with extra water. The more sodium you have floating around in intercellular space, the more water your body is going to send to that space.

Estrogen can puff you up a whole pant size based on water weight alone.

3) Fat deposition

THIS IS WHERE THE WHOLE ISSUE GETS INTERESTING.

Again, estrogen is commonly blamed for the birth control problem. This is somewhat fair. Estrogen promotes fat storage, and particularly in the female areas of the buttocks, hips, thighs, and breasts.

However – the true villain in this story is a certain class of progesterone.

Not all hormones are created equal. One major component of this whole discussion I’ve so far glossed over is the fact that the “hormones” in birth control pills are not actually natural female hormones. They are synthesizsed in laboratories, normally out of plant proteins. Yams are a favored estrogenic contributor to birth control pills, used to synthesize the most popular form of estrogen, “ethinyl estradiol.”

So hormones are synthesized in labs, and not all of them are created equal. There are eight classes of “progestins.” They can be broken down into three broad categories: progestational, estrogenic, and androgenic. Those which act more like male hormones in the body are androgenic.

Research suggests that older varieties of the pill that used more androgenic progestins caused the greatest weight gain. Newer formulations with less androgenic progestins may cause less weight gain according to several studies, such as here, here, here,here and here.

Some more androgenic varieties – ones you might want to avoid, are levonorgestrel and norgestrel. It’s worth noting that levonorgestrel is the most commonly proscribed progestin worldwide.

The three least androgenic forms of progestin and the ones you may want to keep an eye out for if weight gain is a problem are norgestimate, desogestrel, and drospirenone. (But drospirenone has its own risks – read about them here and how they almost killed me here.)

Androgenic progestins like levonorgestrel are still in use for a few reasons. One is that they simply are not a problem for weight gain for the majority of people. Another is that these specific progestins are better at mitigating the risks of estrogen-containing pills than other progestins. They provide better balance. Better balance appears to decrease the risk for vascular thromboembolism and stroke – which is why androgenic progestins are the progestin of choice in most countries. Whichever kind of progestin is right for you is your and your doctor’s own decision.

In sum

To sum up my research:

-Pills high in progesterone – or that do not have estrogen at all – may increase appetite and therefore cause weight gain at least in the short term

-High quantity pills may cause water retention

-Pills high in “androgenic” progestins appears to cause more weight gain than others (norgestimate, desogestrel, and drospirenone)

So does the birth control pill cause weight gain?

In the majority of women, the birth control pill does not cause weight gain, especially if she is on the pill for more than three months. However, studies are conducted on hundreds if not thousands or tens of thousands of women at a time, so even if the average experience is to maintain a steady weight, there will be women who are not average and who do not maintain a steady weight.

Weight gain is listed as a side effect for birth control for a reason. It doesn’t happen to everyone but it does happen to some. Androgenic pills may cause the most weight gain, and water weight and appetite can also come into play. In order to best navigate these options and minimize the side effects you experience on the pill, aside from purchasing my book on the topic, continue reading on this topic in the next installment, How to go on birth control without gaining weight.

More on weight loss for women!

This kind of insight and information is super rare to find online. Rarely do websites that talk about hormones go this in depth into personal experiences and deal with the possibilities of side effects and how to mitigate them (Women to women, or webmd, anyone?). Fortunately, I am one of the few researchers interested in them, and from a paleo perspective!

And many kickass paleo authors are, too!

As luck would have it, 20+ of my favorite paleo weight loss revolutionaries… Diane Sanfilippo, Chris Kresser, Dr Sara Gottfried, me… are getting together for the next three weeks and sharing all their new tricks and tips and their own particular insights (I give a talk on birth control that contains information much like this!)… in a series of FREE talks.

While the event is going on, it’s 100% free. It’s a summit on weight loss, for women only.

Check it out and find more sweet info like this, if you’re into this sort of thing, @ http://forwomenonly2014.com.

Whoopah!

And if you’re interested in a great resource that you can read and benefit from today, check out my excellent book on women’s weight loss “Weight Loss Unlocked” here.