Planned Parenthood Federation of America and Society of Family Planning Briefing Explores New and Existing Research on Contraceptive Use and Obesity
Studies from Society of Family Planning Fellows Provide a Growing Understanding of Safety and Effectiveness of Contraceptive Use among Obese Women and Whether Use of Some Methods Are Likely to Cause Weight Gain among Some Women
February 23, 2012 — Obesity and unintended pregnancy are among this country’s top public health concerns, and the two issues are more frequently intersecting in the realm of women’s health. A group of Planned Parenthood Federation of America and Society of Family Planning physician researchers presented new research on the topics today during a web-based media briefing.
According to data from the National Health and Nutrition Examination Survey, 34 percent of U.S. women between the ages of 20 and 39 are considered obese. A majority of those women will use contraception at some point in their lives, yet few large studies include sufficient numbers of overweight and obese participants to allow for accurate conclusions about this population. As a result, questions remain surrounding the outcomes, efficacy and safety of some birth control methods among obese women.
“A good deal more research needs to be done on the effects of obesity on a variety of medications and medical devices, including birth control,” said Planned Parenthood Federation of America Vice President of External Medical Affairs Dr. Vanessa Cullins. “But a growing body of new and existing researching is emerging to help providers better advise significantly overweight women in selecting the contraceptive methods that are best for them,” added Cullins, who helped present and interpret research on birth control use among obese women during a media briefing held today by Planned Parenthood Federation of America and the Society of Family Planning. The event covered research that was recently completed by Society of Family Planning fellows and is scheduled to be published later this year. The briefing also provided a summary review and interpretation of previously published research on the topic of obesity and birth control.
Among the new findings presented were
· a study that found the levels of pregnancy-prevention hormones varied significantly between obese and normal weight women using the Implanon implant
· research that found young women who gained significant weight after receiving the Depo-Provera contraceptive shot had higher levels of certain fat metabolism enzymes in their fat cells even before they started using the method
“Women want accurate reproductive health information, and those with weight concerns are no different,” said Dr. Melissa Gilliam, board president of the Society of Family Planning and professor of obstetrics and gynecology and pediatrics at the University of Chicago. “They want to know whether certain contraceptive methods are less effective for them, if there are health risks, and whether some methods are likely to make them gain weight.”
In her study, “Pharmacokinetics of Etonogestrel Contraceptive Implant in Obese Women,” Dr. Gilliam and colleagues at the University of Chicago studied the pharmacokinetics of the Implanon contraceptive implant in obese women. Implanon is a highly effective, progestin-only hormonal device that is typically implanted in a woman’s arm and can provide protection against pregnancy for up to three years. Clinical trials for the device excluded women who weighed more than 130 percent of ideal body weight, however. Gilliam’s study measured the active ingredient etonogestrel in obese women during various intervals and found that concentration of the hormone were lower for obese women at all time points compared to established rates for normal weight women.
“These findings shouldn’t be interpreted as showing that Implanon is ineffective at preventing pregnancy in obese women since we did not consider secondary mechanisms by which the implant might prevent pregnancy,” said Gilliam. “But it is a first step in understanding how this method behaves in significantly overweight women.”
In her study, “Biological Behavior of Adipocytes in Adolescents on Depot Medroxyprogesterone Acetate (DMPA): Is It Related to Weight Gain?,” Dr. Andrea Bonny, a Society of Family Planning fellow and an assistant professor of pediatrics with the Division of Adolescent Medicine at Nationwide Children’s Hospital, looked at whether the level of expression of hormone receptors or key fat metabolism enzymes in the fat cells of female teenagers made them more likely to gain weight when using the Depo-Provera (DMPA) contraceptive shot.
“While only a minority of teens gain weight as a result of using the Depo-Provera contraceptive shot, researchers have known for a while that some patients, approximately 25 percent, will gain a significant amount of weight while using Depo-Provera. But currently, we have no reliable method of identifying those girls who might gain weight prior to starting Depo-Provera,” said Bonny. “While our study was small, we were able to show that the young women who gained the most weight had higher levels of expression of certain fat metabolism enzymes in their fat cells even before they started using Depo-Provera. In the future, this discovery could help us identify young women at risk for significant weight gain on depo provera so that they can be counseled appropriately about their contraceptive options. In addition, our findings may help future efforts to prevent weight gain.”
During her presentation, Dr. Alison Edelman, associate professor with the Department of Obstetrics and Gynecology at Oregon Health & Science University, reviewed two of her previous studies looking at birth control pills and body weight. In “Impact of Obesity on Oral Contraceptives Pharmacokinetics and Hypothalamic-Pituitary-Ovarian Activity” Edelman and her colleagues looked at whether drug levels differed between normal weight and obese women taking low-dose combined oral contraceptives and if this in turn, increased the possibility of ovulation. The study did find differences in drug levels – especially at the beginning of pill use and after the seven-day hormone-free interval (period week). Theoretically, obese women may be at greater risk for pill failure during these time periods; however, Dr. Edelman noted that large epidemiological studies have found only slight differences in oral contraceptive failure rates between obese and normal-weight women. She cautioned that: “Although some studies do show a slight reduction in contraceptive effectiveness among obese women, these differences are not sufficient enough to overcome the overwhelming benefits achieved by women finding the method that works best them.”
In a second study, “Combined Oral Contraceptives and Body Weight: Do Oral Contraceptives Cause Weight Gain? A Primate Model,” Edelman wanted to study the impact of birth control on weight in obese versus normal weight subjects. She found that birth control pills where not associated with weight gain in female primates who were given the contraceptive method, and in fact caused a decrease in body weight among obese female primates.
“Weight changes are difficult to track in humans due to all sorts of external confounding factors. This study helps us see the effect of birth control pills on weight in a controlled environment using a model very similar metabolically and reproductively to women,” Edelman said. “It suggests that obese women could experience a weight-related benefit from oral contraceptives as their method of birth control, and it also adds to the wealth of data showing that oral contraceptives do not cause weight gain.”
To hear and see the media briefing link here. The briefing will be available until March 8, 2012.