The Real Truth About Weight Gain and Contraception

Here’s the down-low on how different methods of contraception impact weight gain.

January 21, 2013  |  

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Come post-holiday season, many of us feel a little outside our comfort zone weight-wise, and we look at all kinds of factors: diet, exercise, sleep, supplements, meditation, hypnosis, psychotherapy, even surgery that might help us tip the scales a little less.

For many women, one question that inevitably comes up is whether contraception is making weight management harder. Modern Western women spend almost 40 years trying not to get pregnant. We have close to 400 fertile cycles out of which we want to get pregnant maybe once or twice or four times or not at all. That’s a lot of women spending a lot of time engaged in some kind of contraception, and consequently rumors abound about contraceptives and weight gain. What’s real?

The real scoop includes some bad news: Normal healthy women gain weight during their fertile years with or without contraception. At age 20, American women weigh on average 125-130 pounds. By age 55, the average is closer to 165, a total gain of 35 pounds. (Weight gain during the teen years is even more rapid, an average of 30 pounds in six years. Even long-distance runners tend to gain over time.) The net-net is that any time a woman is contracepting is a time she is also likely to be gaining weight, regardless of any effects from contraception. This is borne out in the fact that in all clinical trials of contraceptives some percentage of women complains of weight gain, and consequently, virtually all contraceptives subsequently list weight gain as a possible side-effect. Only after the fact, as data accumulate, are researchers able to tease apart normal weight gain from possible effects of contraceptive hormones.

This means that as a woman trying to figure out what is best for your body, it can be challenging to sort out reality from hype or haze. The best research compares women with and without a given method over a span of months or years, but research like that can be hard to find. The kind of information that spreads the fastest and furthest is stories. Anxiety, in particular, is contagious, which makes scary stories particularly viral.

Sometimes we forget the big picture: Pregnancy and childbearing have such big effects on our bodies that with rare but noteworthy exceptions the most significant health question related to any contraceptive is– how well does it work? Many women don’t realize how often most contraceptives fail with “human factors” built into the equation. On the Pill, 1 in 12 women gets pregnant each year; relying on condoms alone, that rate is 1 in 8. (For no contraception the annual rate is 85%; abstinence commitments may cut that 85% rate by about half.) With a long-acting method like an implant or IUD, the pregnancy rate drops to 1 in 500 or less. If you are concerned about managing weight for health or lifestyle reasons, efficacy should be a primary consideration in choosing among contraceptive options.

Independent of the question of efficacy, the best research available suggests that most contraceptives have little effect on weight, with a few important exceptions. Here is the lay of the land.  

IUD’s: The copper IUD is in the top category for efficacy (99%+) and at the same time is a completely non-hormonal method. This means that, despite some challenges in insertion and adjustment, it is the gold standard for women who want no artificial hormones. Its only effect on weight is through reducing unintended pregnancies. Hormonal IUDs boost contraceptive effectiveness (and also decrease menstrual symptoms) by releasing a mostly local micro-dose of a progestin, Levonorgestrel. When it comes to weight gain or loss, though, the difference appears minimal. One study showed slightly more gain in hormonal IUD than copper IUD users, but a longer study found that women with hormonal IUDs gained slightly less weight than women with no hormonal contraceptive. Other research reported modest weight loss for women on both kinds of IUD. Since the differences appear small and inconsistent, don’t assume either IUD will prevent normal weight changes.