The Truth About Birth Control and Weight Gain

Google “Birth control AND....” and one of the top 3 suggestions, unsurprisingly, is weight gain. Weight gain has long been a belief and fear of women seeking contraception, partially due to its development history.

When first formulated, contraceptives had larger dosages of hormones, which often resulted in weight change. Today there are a great variety of contraceptive options in formulation, delivery and much lower dosage of hormones, yet the belief in weight gain as a potential side effect persists.

Controversy over birth control and weight gain exists today because of the numerous research studies that claim that weight gain is not a common side effect, challenging the overwhelming number of anecdotes from women claiming (what they consider to be) significant upticks on the scale.

So, why is there disagreement, leading us to question the claims from research, doctors and the pharmaceutical companies? This is an important question to answer, since weight gain is a frequent reason for discontinuation of birth control among female users, seemingly overwhelming the rationale for seeking out contraception in the first place!

Before understanding the mechanisms of the hormones in contraceptive methods—estrogen and progesterone—it may be helpful to take a journey back in time to when these hormones surged, at puberty. Experience varies at puberty, but most women experience a widening and thickening of the hips and thighs and an enlargement of the breasts. This is due not only to surges in estrogen as the ovaries begin to mature and release eggs, but also due to surges in growth and thyroid hormones.

However, it is estrogen that brings about the most obvious changes in physical appearance for a female. Estrogen also brings about an increase in metabolic rate that occurs during puberty because women are now producing eggs, and estrogen is one part of that process, like fuel for an engine. The timing of puberty, genetics, food intake and level of physical activity in which a female is engaging during puberty all combine and lead to some girls becoming leaner as they grow, and others taking on a more curvy appearance.

Now lets jump ahead several years to menopause. Women typically experience weight gain, especially around the abdomen as estrogen levels drop back to pre-pubertal levels. Why then would estrogen cause weight gain? Without estrogen at the levels of fertility years, women have a greater tendency to deposit any excess fat in the abdomen, and without producing eggs and menstruating, metabolic rate will decrease slightly, along with the rate of many other physiologic processes with age. It seems like estrogen just can’t win, doesn’t it? It’s blamed for weight gain when added in while on birth control, and blamed for weight gain when it drops during menopause!

Now, what about progesterone? When an egg is matured and released, the follicle, or bed in which the eggs matured turns into a structure called the corpus luteum, which produces progesterone. You may have noticed that when you’re not taking contraceptives, your weight rises and falls throughout the cycle in a typically predictable pattern. This is largely driven by water retention. Estrogen acts on receptors in the kidneys, causing them to retain water. Progesterone has the opposite effect, actually acting slightly as a diuretic. Right before the period, if no pregnancy occurs, progesterone will rapidly drop off, causing a rebound effect of increased water retention, weight gain and bloating, before the period arrives.

Hormonal contraceptives smooth out the fluctuations in either one or both of these hormones, depending on whether you are on a progesterone only method or combined estrogen and progesterone. To suppress ovulation, progesterone must always be present. Since it is released to prepare the uterus for pregnancy, it suppresses the maturing of another egg, convincing the brain that the uterus is “busy” and cannot support another pregnancy. This makes pregnancy highly unlikely, unless dosages are missed or irregular.

Estrogen and progesterone affect a variety of endocrine functions, so it would be silly to suspect that adding extra exogenous hormones to your body would not have some side effects.

Theoretically, the estrogen in birth control would cause increased water retention, potentially causing weight gain. However, some women experience no change in weight, and some even lose! As far as progesterone is concerned, since it decreases water retention, it stands to reason that progesterone only methods should result in weight loss.

However, this isn’t what women report experiencing, particularly on the DEPO-provera injectable. What is going on here? Simply put, any time we adjust the levels of any hormones that affect water retention, the body responds in an unpredictable way, just like when we eat something different, engage in new physical activities, or travel to a different climate. That is why some doctors and other health professionals suggest giving a new hormonal contraceptive at least 3 cycles to “level out” before panicking about weight gain and other side effects. Unfortunately, too many doctors may shrug off a woman’s concerns about weight gain and birth control, attributing it to other factors. As it stands, they have the research on their side.

What The Research Says

Without spending all day reading the research on hormonal contraceptives and weight gain, here are the key findings from several randomized control trials, surveys and systematic reviews:

• Combined hormonal therapy: A Cochrane database study in 2011 that included 49 trials found that evidence was “insufficient” to determine the effect of combination contraceptives on weight, but “no large effect” was evident. Only four studies had a placebo group comparison, making it difficult to definitely attribute any weight gain seen to the contraceptives. Other studies have found similar non-significant or “minimal” weight gain, whether combination oral or in patch form.

• Progesterone-alone (oral): inconclusive at best, with either no, or average, weight gains of five pounds in most studies up to 12 months.

• Progesterone injectable: this is where the strongest evidence for weight gain is found, still amid conflicting results. A 2009 study of Depo-Provera (Depo-medroxyprogesterone) reported that shot users gained an average of 11 pounds in three years, yet offered no conclusive explanation as to why.

So overall, the research does not support weight gain among birth control users.

Let's Take A Closer Look

Now, lets get to the problems with applying population-based findings to individual women. All research is going to be based on statistics and the masses, not the individual. This is true for any drug reaction or interaction. How many people do you know are allergic to peanuts? Probably not many, yet those who do may have dangerous responses to them. Would it be fair to say on a jar of peanuts that they cause anaphylactic shock? No, because no one would eat them! But, is it true statement? Of course...for some. This is the heart of the confusion around birth control.

For starters, the data available that supports a lack of weight gain may come mostly from women who have been on birth control long term because they didn’t experience weight gain, and researchers aren’t hearing from the women who discontinued or gave up due to weight fluctuations.

Second, lets be fair and look at the statistics on weight gain throughout our age. The majority of adult women gain weight over the years, so a 28-year-old woman may pinpoint the beginning of her weight gain after college, around say age 23, when she also started using birth control. She may unfairly attribute her weight gain over the years to her birth control use. Another plausible reason for gradual weight gain on birth control is if women (or men!) adjust their food intake, eating more with their partner and being less active in favor of spending time with them, while at the same time. So, the more gradual the weight gain, the more difficult it can be to isolate birth control as the causative agent.

Finally, what is considered a significant weight gain may vary greatly from study to study and person to person. A study may find that an average weight gain of five pounds in three months is not “statistically significant.” But this may be a dramatic gain to a woman who is particularly weight-conscious. It is also important to remember that if a study reports a “mean” gain of five pounds over a period of time, that means that many people experienced less and many people experienced more.

Now, who do you think, of those people, are going online and reporting their weight fluctuations with birth control? Bingo. The ones who gained. Just like with anything else, whether a restaurant or another service, the least satisfied among us are usually the most vocal.

Some women's bodies will have larger reactions to the adjustments in hormone levels and will take longer to normalize. Or they may never normalize, and a new medication need be tried. There are many different formulations of synthetic hormones, so that one prescription of progesterone or estrogen may not behave in your body the same way as another.

If you experience a rapid weight gain in the first few days or weeks of birth control, give it at least three months, tracking to see that your other behaviors that affect your weight aren’t also potentially to blame. If you are uncomfortable, or your weight does not level out, you could talk to your doctor and try a different formulation, or consider alternative forms of contraception. There’s no reason to be uncomfortable, especially when it comes to your health and well being, but there is reason to think rationally about what these hormones are doing in your body, instead of panicking or feeling out of control if the scale ticks upward.

What Should You Do?

To summarize, the research is inconclusive, but there is enough evidence to say that most women do not experience much weight change on the majority of contraceptive forms. There are problems with the research, as we discussed. At the same time, the anecdotes about weight gain with birth control, especially when they occur rapidly, are not necessarily wrong, but they may scaring women out of using contraceptives.

If you are currently thinking about going on hormone contraceptives and this is a major sticking point in whether or not you should use them, consider all the information in this article and explore all the available birth control options so that you can make a rational decision as to which is the one that’s right for you.

For more on this topic, check out this article from Dr. Brooke Kalanick who discusses the effects birth control may have on women with certain hormone issues/irregularities like Hashimoto's and PCOS.

As you can see, while much of the available research doesn’t show a correlation between taking the Pill gaining weight, the effect it may have on your body depends on your unique hormone mix. Other things that can have an effect on your hormones and help you manage your weight include a smart training program and sound nutrition habits.