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DMPA and weight gain: Science considers link
The next patient in your exam room is a 17-year-old female who uses the contraceptive injection depot medroxyprogesterone acetate (DMPA) for birth control. She has been using the method for about a year. She tells you she has gained about 10 pounds since initiating the method. What is your next move?
Findings from a new study indicate that women using DMPA gained an average of 11 pounds and increased their body fat by 3.4 % over three years.1 The amount of weight gain was dependent on the length of time DMPA was used, as the rate of weight gain slowed over time, data suggest.
Clinicians should tell women that there is an increased risk with weight gain while using DMPA, says Abbey Berenson, MD, professor in the Department of Obstetrics and Gynecology and director of the Center for Interdisciplinary Research in Women's Health at the University of Texas Medical Branch in Galveston. However, not all women who use this method will gain weight, and it is a highly effective method of birth control, notes Berenson, who serves as lead author of the research.
"Unfortunately, it is difficult to predict who will gain weight and who will not," she says. "At this time, the best advice we can give is to monitor [patients'] weight and, if they experience significant weight gain during the first six months, they may want to consider using another method."
Weight gain is common in many women who use DMPA; however, this effect is not consistent for all women, state authors of Contraceptive Technology.2 Counsel on weight gain prior to method initiation. Weight gain is commonly cited as a reason for discontinuation of DMPA, with 12%-19% stopping use for this reason.3
Review the research
To perform the study, researchers followed 703 women in two age categories: ages 16-24, and 25-33, using DMPA, a combined oral contraceptive (OC), or nonhormonal methods (bilateral tubal ligation, condom, or abstinence) for three years. DMPA users who discontinued use of the injection and selected another form of birth control were followed for up to two additional years to examine the reversibility of the observed changes. Throughout the study, researchers compared changes in body weight and composition and analyzed the influence of age, race, caloric intake, and exercise among the study population.
When researchers compared all three groups, DMPA users were more than twice as likely as women using OC or nonhormonal methods to become obese over the next three years. Over 36 months, DMPA users increased their weight (+5.1 kg), body fat (+4.1 kg), percent body fat (+3.4%), and central-to-peripheral fat ratio (+0.1) more than Pill and nonhormonal method users (P < 0.01).
Women using oral contraception did not gain more weight than those using a nonhormonal form of birth control. However, the study found that their body fat increased slightly while their lean body mass decreased. Researchers said this was less likely among those women who exercised regularly and consumed a healthy diet that included increased protein intake.
After discontinuation of DMPA, some decrease in body weight and fat (0.42 kg in six months) occurred when nonhormonal methods were used, researchers report. In comparison, those who used the combined pill formulation after DMPA discontinuation gained 0.43 kg in six months.1
What causes gain?
Previous research indicates that DMPA is associated with significant weight gain compared with an oral contraceptive or no contraceptive.4 In a study that looked at adolescent girls initiating DMPA, OC, or no hormonal contraceptive method, scientists found a significant relationship between baseline obesity status and subsequent weight gain.4 Teens who were obese (body mass index kg/m2 30 or above) prior to use of DMPA gained significantly more weight than obese girls starting the Pill or no contraceptive method. In addition, obese adolescents using DMPA gained more weight than did nonobese adolescents using DMPA, OC, or no hormonal contraception method.4
Some researchers have hypothesized that the relationship between DMPA and weight gain may lie in behavioral eating or exercise; however, the link might be found at the metabolic level, suggests Andrea Bonny, MD, assistant professor of pediatrics at Case Western Reserve University School of Medicine and MetroHealth Medical Center in Cleveland. Bonny and fellow researchers are looking at this question, with research findings tentatively scheduled for release in the next year. "My personal guess is at this point is that something is happening metabolically at the level of the fat cell," she says, "and what is driving that, I don't know if we're entirely clear on, whether it's driven by the lack of estrogen or a direct effect of progesterone."