Evidence that birth control pill causes weight gain a little light on data

Though today’s oral contraceptives are less likely to cause weight gain because of a lower estrogen dose, many young women are still hesitant to use the pill for fear of packing on extra pounds. Nearly one-third of women on birth control pills stop using them within a few months because of undesirable side-effects, especially perceived weight gain. One of the latest studies to tackle the issue of whether birth control can cause weight gain was a 2008 meta-analysis of 47 studies conducted by Cochrane Reviews. Its conclusion: “The evidence was not strong enough to be sure that these methods did not cause some weight gain.” In other words, the authors don’t have strong evidence for or against the theory. A more recent study found no association between oral contraceptives and weight gain, but it was conducted on rhesus monkeys — used because they supposedly have reproductive systems quite analogous to ours.

“Whether on oral contraceptives or not, women during their child-bearing years gain an average ten pounds a decade,” director of the Center for Interdisciplinary Research in Women’s Health Dr. Abbey Berenson tells the Los Angeles Times. Further, many teens and young women on the pill are also transitioning into a different lifestyle, such as college, a new relationship or marriage, which may lead to diet or exercise modifications that can also lead to weight changes.

ACSH's Dr. Gilbert Ross wonders if in the case of young women who smoke, taking their doctor’s advice to quit before getting on the pill in order to reduce their risk of adverse side effects may also act as a confounder because smoking cessation may lead to weight gain. “My advice: while most women do not actually experience real weight gain on the pill, if you notice a weight change, whatever the underlying physiology may be, you should discuss it with your physician. Oral contraceptives are very safe and effective, but there are many birth control options. Using comprehensive safe sex practices is very important, because unintended pregnancy is also a serious health concern.”