The Pill & Weight Gain: The Link

One of the side effects of taking the pill for many women is that they can gain weight, sometimes excessively. Women who opt against the oral, daily contraceptive pill and opt for a single birth control shot are often affected even more with weight gain. Now, researchers at the University of Texas Medical Branch in the US have identified women who are likely to gain weight while using the depot medroxyprogesterone acetate, commonly known as Depo-Provera or the birth control shot.

Dispelling the myth that all women who use the birth control shot will gain weight, the researchers found that users whose weight increased by 5 percent within the first six months of use, called “early gainers,” are at risk of continued, excessive weight gain. While 75 percent of users gained little or no weight, the early gainers averaged weight gain of 24 pounds over three years, the researchers claim.

The Pill & Weight Gain: Greater Health Risks

Commenting on the weight gain experienced by many women using the birth control shot, Dr. Abbey Berenson, said, “Weight gain is linked to increased abdominal fat, a known component of metabolic syndrome, which raises the risk of obesity-related conditions such as cardiovascular disease, stroke and diabetes.”

Depot medroxyprogesterone acetate (DMPA) is an injected contraceptive administered to patients every three months. According to the American College of Obstetricians and Gynaecologists, more than 2 million American women use DMPA, including approximately 400,000 teens.

DMPA is relatively inexpensive compared with some other forms of birth control, has a low failure rate and doesn’t need to be administered daily, which contributes to the contraceptive’s popularity.

The researchers recommend that doctors closely monitor weight at each three-month follow-up visit and suggest a different contraception method to patients who gain significant weight within the first six months of use.

Researchers found that early gainers exhibited three major risk factors: A body mass index under 30, having children before starting and a self-reported increase in appetite after six months of use.

The study, which appears in the August issue of Obstetrics and Genecology, followed 240 women ages 16-33 who used the contraceptive shot for up to three years. Researchers looked at several potential predictors of weight gain, including age, race, baseline obesity prior to using the shot, lifestyle variables such as smoking and exercise level, and weight gain at six months.

They found that those who had gained more than 5 percent of their body weight within six months, or after just two injections of DMPA, continued to gain significant weight during the next 30 months.

While previous studies have associated birth control-related weight gain with a higher BMI, Berenson’s study suggests that a lower BMI - under 30 - is more predictive.

“The amount of contraceptive administered to a woman does not change based on weight, as occurs with some medications,” Berenson said.

“The drug may be more concentrated in the tissue of a woman with a BMI under 30 and may contribute to excessive weight gain, but more research is needed.”

The biological mechanism of contraceptive shot related weight gain is still unknown, but researchers note that possible mechanisms include glucocorticoid-like activity, how the body breaks down simple carbohydrates such as glucose, and DMPA-associated interference with insulin action.

Previous findings seem to argue against the theory that weight gain could be due to the drug’s perceived effects on increased caloric intake and decreased energy expenditure, but ongoing research is needed to confirm or discount varying possible explanations.

This study builds upon UTMB research released earlier this year that found DMPA users gain significant weight not seen among women using oral or nonhormonal contraception.