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Gaining weight: Is it the birth control?

If those skinny jeans are feeling a bit too skinny, don’t assume your birth control is the cause.

by Jessica Morse, MD, MPH

It’s a very common story. A woman starts using hormonal birth control, finds herself gaining weight, and assumes the birth control is to blame. The tricky thing is that lots of research about hormonal birth control shows that, with one important exception, it’s probably not the birth control.

A note on personal experiences vs. the big picture

Before we lay out the evidence, we want to acknowledge the difference between looking at lots of women on average versus an individual woman. Research tells us about women on average, but not about specific women’s experiences. When we describe what happens for women on average, we are not dissing personal stories. (Bedsider has big love for personal stories!)

Here’s why the big picture is important: it sets our expectations. Being influenced by our expectations is a basic part of human nature. That’s why the placebo effect exists.

The big picture

Researchers have looked at whether hormonal birth control makes it more likely to get bloated or hungry. They’ve also looked at women’s weight changes over time when using specific birth control methods and compared them with women using methods with no hormones. With one exception, they’ve found no direct link between using hormonal birth control and gaining weight. Here are the details.

IUDs. There are two kinds of IUDs. One kind releases a low dose of progestin hormone (Mirena and Skyla) and the other kind has no hormones (ParaGard). Both kinds of IUDs mainly work inside the uterus, so there are minimal effects on the rest of the body. Studies show no difference in weight changes between women using hormonal IUDs and women using birth control without hormones.

The implant. The implant also releases a low dose of progestin hormone. Because the implant is relatively new, there are fewer studies about it. Early studies showed that about 5% of women using the implant got them removed due to concerns about weight gain. However, the weight changes don’t appear to be different between women using the implant and women using birth control without hormones.

The pill, the patch, and the ring. Birth control pills contain both an estrogen and progestin hormone, and are probably one of the most studied medicines on Earth. Many studies show that the pill does not cause weight gain, yet concern about weight gain is the main reason why women quit taking it. The ring and the patch are similar to the pill in terms of their ingredients and dose, so are not likely to cause weight gain, either.

That important exception

The shot. Most women don’t gain weight because of the shot, but some do. Interestingly, weight gain on the shot seems to be more common in young women who are already considered overweight. Additionally, the women prone to gaining weight because of the shot will usually notice a change within the first six months. If weight gain is absolutely not okay for you, the shot may not be the best choice.

The takeaway

Understanding all of the details that can affect weight—like diet, exercise, and genetics—can feel overwhelming. The tendency is for people to gain weight throughout their lives, so being a year older is more likely to cause weight gain than birth control. But like we said—this is on average and doesn’t take into account women’s personal experiences. If you think your birth control is affecting your weight in a way you don’t like, talk to your health care provider to find another effective method that works for you.

No matter what birth control you’re using, it’s important to get a daily cardiovascular workout. And no one says you have to leave the bedroom for that.

Jessica Morse is an ob/gyn at UNC where she works with residents providing a full spectrum of reproductive health care. Her main research interest is making sure women get the birth control they want, when they want it. She lives in Durham, NC, with her husband and silly 5-year-old son, where they spend weekends hiking, hanging out at playgrounds, and exploring the Bull City.

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