Medical Professionals Weigh in on Weight and Birth Control

Americans are bigger than ever. More than 70 percent of U.S. citizens older than 19 are overweight or obese, as are more than 20 percent of 12 to 19 year olds, according to the Centers for Disease Control and Prevention.

This trend in weight has even entered the conversation about sexual health, as some people question whether popular contraceptives are as effective on overweight or obese women.

ATTN: got an answer to that question.

A 28 day pack of birth control pills.

First, we should define the general criteria for overweight and obese, which is largely based on the body mass index. BMI numbers are determined by a formula using height and weight. The CDC offers a basic online calculator to help you figure it out.

The National Heart Lung and Blood Institute in the U.S. Department of Health and Human Services also offers a chart.

The National Heart Lung and Blood Institute's Body Mass Index chart.

A BMI between 25 to 30 is considered overweight and a BMI greater than 30 is considered obese, according to the CDC. However, BMI is a general guideline or indicator and "not diagnostic of the body fatness or health of an individual," and critics say it's an outdated way to determine a healthy weight.

With the BMI caveat, is birth control actually less effective for overweight or obese women?

ATTN: talked to health professionals about body weight and birth control to find out. The answer is 'probably not, but maybe.'

A study by Federal Food and Drug Administration researchers published in 2015 found that obese women taking combined oral contraceptives may have a higher risk of pregnancy, compared to non-obese women, but more studies are needed.

A birth control pill.

Birth control pills may be less effective for obese women who have undergone weight loss surgeries, specifically because their bodies absorb less. "In obese women who elect to have surgical weight reduction, restrictive surgery as in banding should be ok, but with gastric bypass and procedures that interfere with absorption, it could be a problem," Anne Moore, an advanced practice registered nurse and a doctor of nursing practice, told ATTN:.

However she said there is a lack of "compelling data" that says birth control methods are less likely to work on overweight or obese women overall.

"It's certainly been an urban myth, but the data hasn't really borne out that there's much of a reason for concern," said Moore. However, she also noted that most of the studies on hormonal birth control have excluded women who are greater than 130 percent of their medically ideal body weight.

Dr. Aparna Sridhar, an assistant professor of obstetrics and gynecology at the University of California, Los Angeles, told ATTN: via email that there is "insufficient evidence" on the topic, but that daily hormonal birth control pills may be less effective on women who are overweight.

"Overall, overweight and obese women appear to be at a similar or slightly higher risk of pregnancy compared to normal weight woman," said Sridhar. "There is no specific BMI that is established by scientific evidence at which the pills will be less effective."


She added that there may be some additional risks with hormonal birth control for obese women, but they are minimal.

"There is theoretical concern of higher risk of clots in legs or lungs in obese women who use birth control pills containing estrogen and progestin (combined hormonal contraceptives)," she said. However, she said this theoretical risk doesn't outweigh the real benefits of preventing unwanted pregnancies.

For obese women, both experts recommended IUDs or implants, as they're often the most effective and eliminate the human error component of taking birth control pills at the same time every day. Moore encouraged all women to get more information about birth control methods, and make the best choice for them.

"I hope that these options are well-known to everyone and we lay out the full menu so women can be empowered," she said.

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