(NaturalNews) Some hormonal birth control methods may increase the risk of diabetes in overweight but otherwise healthy women, according to a study conducted by researchers from the University of Southern California and published in the journal Contraception.
The researchers divided a group of obese women into three groups. The first group consisted of women who were using any non-hormonal birth control method, including condoms, sterilization (male or female) or the copper intrauterine device (IUD). The second two groups consisted of women using long-acting reversible contraception (LARC) based around the hormone progestin. Women one group used a progestin-releasing IUD; women in the other group used a progestin-releasing device that was implanted under their skin.
The study did not include women who were using other progestin-based birth control methods such as pills, rings or injections. It also did not include women using birth control based on hormones other than progestin.
Progestin is a synthetic version of the female sex hormone progesterone, which plays a critical role in pregnancy. Progestin is one of the hormones used in hormone replacement therapy (HRT), which was once widely used to treat the symptoms of menopause until it was shown to increase women's risk of heart disease, cancer and early death. Progestin injections have also been linked to failure of fertility treatments.
The researchers found that all the birth control methods included in the study were effective, and that none of the participants experienced changes in weight, cholesterol levels or blood pressure between the beginning and end of the study.
Women with the skin implant experienced a 10 percent increase in fasting blood-glucose levels over the course of six months; however, while women with the progestin-releasing IUD experienced a five percent increase. Conversely, fasting blood glucose levels actually decreased by two percent in the control group. Insulin sensitivity also decreased in both LARC progestin groups in comparison with the control group. Both of these changes indicate an increased risk of developing diabetes. The effect is particularly striking since there was no increase in other diabetes risk factors, such as weight.
The findings support the results of a prior study conducted by the same researchers, which found that obese women who received a progestin shot every three months also had an elevated diabetes risk.
"Overall, we're finding that methods such as the progestin injection and the progestin skin implant, which both have higher circulating progestin, may have an increased risk for metabolic changes," researcher Penina Segall-Gutierrez said.
Segall-Gutierrez noted that the researchers' focus on obese women is especially important.
"Contraceptive studies often only look at normal-weight women," she said. "Studies such as this are necessary because, today, one-third of women in the U.S. are overweight and one-third are obese. All women, including overweight and obese women, need to have access to safe and effective contraception."
Obese women are already advised not to use estrogen-based hormonal contraception, because these drugs are known to increase the risk of blood clots, which can be especially dangerous for those with already compromised cardiovascular health.