Contraception: Do the pill and other combined hormonal contraceptives cause weight gain?

Weight gain has not been conclusively proven to be an adverse effect of using the contraceptive pill, patch or ring. Many women have a problem with weight gain as time goes by, whether or not they use hormonal contraception.

Combined hormonal contraceptives include the oral contraceptive pill (also called OCP or simply "the pill"), the contraceptive patch and the contraceptive vaginal ring. They are called combined contraceptives because they include two forms of hormones: an oestrogen and a progestin. There are also pills with only one hormone in them (often called "mini pill"). For many women, hormonal contraceptives are a very convenient form of birth control, because no preparation is necessary around the time of having sex and the contraception is under the woman's control. You can read about how hormonal contraceptives work here.

The pill is the most widely used form of birth control in many countries. But one of the more common reasons women report for stopping using the pill is that they believe it has been causing them to gain weight. Because women have reported both weight gain and weight loss while using these contraceptives in clinical trials, possible weight gain and weight loss are listed as adverse effects on the product information of hormonal contraceptives. However, the issue of whether or not contraceptives can truly cause weight gain is controversial. The reason for this is explained below.

The controversy on weight gain and hormonal contraceptives

Weight gain is often caused by one of the following factors:

• Fluid retention or bloating
• Increased muscle (because muscle is heavier than other tissue)
• Deposits of fat

There are several ways that hormonal contraceptives could theoretically cause weight gain, but none have been proven. Oestrogen used in hormonal contraceptives could hypothetically lead to fluid retention and increased fat. Combined contraceptives could affect women's appetites, which might make them eat more. Some hormones could increase muscle mass, but this is most unlikely to be an effect of contraceptives.

The main reason why it is assumed that hormonal contraceptives lead to weight gain is that some women (and men) tend to gain weight over time, regardless of whether or not they use hormonal contraceptives. To be sure about whether or not contraceptives are adding to the problem, trials would need to have groups of women not using hormonal contraceptives to compare their weight over time with similar women who were using hormonal contraceptives.

However, although there are many trials of hormonal contraceptives, because these contraceptives are so effective, they are usually compared only to other hormonal contraceptives, not to dummy tablets (placebos) or other forms of contraception. What is more, women in trials of contraceptive methods are not routinely weighed before and after they start using the contraceptives. That means that researchers in the trials may be recording when a woman says she stopped taking the contraceptive because of weight gain, but there is no way of being certain that more weight was being gained in one group or another.

To try to resolve this controversy, researchers from the Cochrane Collaboration looked for and analysed trials on hormonal contraceptives that measured weight.

The results from trials: no strong evidence of a link between contraceptive use and weight gain

The Cochrane researchers could only find 3 trials with around 1,250 women that compared combined hormonal contraceptives with placebos while also measuring the impact on weight. One of these trials was done more than 30 years ago on a higher dose contraceptive than would be used today. None of the trials found a definite link between hormonal contraceptives and weight gain. But these few trials were not big enough to be able to provide a definite answer.

The researchers also found another 41 trials where weight gain was measured, and different hormonal contraceptives were compared with each other. Because there are so many different types of hormonal contraceptives, even this number of trials was not enough to provide evidence about every type of contraceptive. And these were not ideal trials for answering the question for many other reasons. However, the researchers concluded that there was no strong evidence of an effect on weight gain in these trials either.

Further, weight gain was not higher in the groups with higher doses of hormones. If weight gain was definitely an adverse effect of hormone use, then you would expect higher doses to lead to more weight gain. Although the fact that they did not is not enough to disprove the theory of weight gain from hormonal contraceptives, it does make a genuine link less likely.

The researchers concluded that it seems very unlikely that hormonal contraceptives cause a major gain in weight. If that were true, then that would have been apparent from the research that has already been done. However, this conclusion does not rule out that individual people may gain weight.

If you are using a hormonal contraceptive and you believe it might be responsible for weight gain, one of your options is to talk with a doctor about trying a different type of hormonal contraceptive. There are many brands and combinations, including very low dose options. There are also other, non-hormonal contraceptive options to consider, with different advantages and disadvantages compared to hormonal contraceptives.


Author: German Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)