The pill may not make you ill, specialists say, as each woman responds differently to its hormonal effects

Since its creation in 1960, the birth control pill has been used by 85 percent of all women at least once in their life.

But women often respond differently to the pill, making it difficult to assess whether the pill always leads to side effects like weight gain, said Radhika Rible, assistant clinical professor of obstetrics and gynecology at UCLA. The pill contains synthetic forms of the hormones estrogen and progesterone, which work to suppress the release of other hormones responsible for initiating the process of ovulation. Sarah, a third-year physiological science student whose last name has been omitted for medical privacy, was certain she would gain weight while taking the pill after talking about its effects with friends and family.

But she was more concerned with clearing up her acne and being able to regulate her menstrual cycle, two benefits sometimes experienced by pill users.

Researchers and doctors are familiar with estrogen’s ability to suppress androgen hormones, which are found in trace amounts in women and are sometimes responsible for acne, Rible said. But the explanation for weight gain is more mysterious.

A 2010 UCLA study by Nancy Grossman Barr, an assistant professor of family medicine, showed the pill is unlikely to increase weight independent of lifestyle choices. But the hormones estrogen and progestin may alter mood and appetite changes and therefore indirectly alter weight, Rible said. Hormones may also cause some women to retain more fluid, leading to an increase in water weight, she added.

Regardless, most weight gain is minimal, Rible said. Although Sarah gained about five pounds, she also goes to the gym regularly and maintains an active lifestyle.

Some women do not experience side effects even after being on the pill for years, Rible said. Nicole McIntyre, for instance, spent four years on the pill without putting on any weight. She went on the pill because she was hoping to find a cure for her painful menstrual cramps, which sometimes kept her out of classes in high school.

Women who do experience side effects like weight gain can try out different dosages until they find one that minimizes or eliminates side effects, Rible said. Various forms of the pill do not show significant differences in the intensity of some symptoms, including breast tenderness, mood changes and nausea, according to Grossman’s study.

McIntyre plans on sticking to her pill regimen to reduce her cramps, but Sarah ended hers after finding out that it raised her blood pressure to dangerous levels. While she also lost the associated weight, she said having high blood pressure was a better reason to quit than being able to lose a few pounds.