The Oral Contraceptive Pill (OCP)
The Oral Contraceptive Pill (OCP) or birth control pill belongs to a class of birth control compounds called hormonal contraceptives. The basic science behind them is to interrupt the normal release of hormones in the female that lead to ovulation, or the release of an egg. If there is no egg released, no fertilization can occur. OCPs may also make periods milder, more regular and help control some conditions such as endometriosis. The overwhelming majority of women in the United States use OCPs at some point in their lives. Recently, a large-scale survey of women in America indicates that about 82 percent have used OCPs at some time between age 15 and 44 and at any given time about 20 percent of the women in this age range are using OCPs. Between 20 and 60 percent of women will discontinue using OCPs because of side effects such as headaches, mood changes, and weight gain. Many hormonal contraceptives list weight change as a side effect. This point of this article is to discuss OCPs and weight gain.
Weight gain - what the research says: There is a decent body of research suggesting most women will experience little to no weight gain from OCPs when compared to women using no hormonal control or other methods. Several such studies are described here:
- A study using adolescents evaluated weight gain in OCPs users compared with those receiving depot medroxyprogesterone acetate (Depo-Provera®). It found no significant increase in the weight of OCP users, but those using the depot injection, however, did see some significant weight change. Weight gain and depot is discussed later.
- In the O'Connell study mentioned above, no weight gain was attributed to OCPs or NuvaRing® for a period of three months.3
- The majority of OCP users in a study designed to find out why women quit using OCPs did not gain weight. Around 20% of the participants in this study gained weight, but more than 75% either lost weight or experienced no change.2
- Another study of adolescents grouped users by starting weight. Participants were then separated into groups using Depo, OCPs, or no hormonal contraceptives, but were also grouped into either non-obese or obese categories. In this study, OCP use was associated with no weight gain in the obese category and a smaller increase in the healthy weight category than non-hormone users. In fact, the non-obese and obese girls not using hormones gained more weight (7 to 8 pounds in a year and a half) than either group of OCP users. Obese OCP users gained less than a half-pound and non-obese OCP users gained 6 lbs in the same period.
The bottom line is that a large number of recent studies provide little evidence that using an OCP causes weight gain in either obese or non-obese women.
What about Depo?
Depot Medroxyprogesterone acetate is a different method of hormonal contraceptive. Users receive an injection every three months and take no pills. Several studies have shown a significant increase in body weight for users, which seems to be worse for heavier women in stark contrast to OCPs. One older study from 1995 compared groups of women using three types of contraceptive hormones and found negligible changes in body weight. Thus, there may be a select group of women who have an easier time gaining weight than the average depot user. This group may represent women who are heavier at the start of depot use.
In a study comparing OCP users with Depot, the majority gained less than 5% of their original weight. A much larger number of users of Depot gained >10% of their starting weight. It appears that women who use birth control pills will experience minimal or no weight gain due to the pill and those who use Depot may be at greater risk of gaining weight. But remember - you can always prevent weight gain or lose weight by increasing your activity level (daily steps, short walks, exercise, etc.) and eating fewer calories.