Birth Control Shot Linked To Weight Gain

By Margarita Nahapetyan

The birth control shot, which appears to be the most popular contraceptive choice, especially among younger women, can lead to an extreme weight gain and a body fat increase, according to a study that appeared in the latest issue in the American Journal of Obstetrics & Gynecology.

Depot medroxyprogesterone acetate (DMPA), most commonly known as the birth control shot, is an injected form of birth control that is being administered to patients every three months. More than 2 million women in the United States, which includes almost 400,000 teenage girls, prefer this contraceptive method. The popularity of DMPA can be explained by its lower costs compared to other birth control forms, as well as by its low failure rates and the fact that there is no need to use it on a daily basis.

However, the scientists found that women who have been using DMPA, gained an average of extra 11 pounds and increased their body fat by 3.4 per cent over the three-year period of time, compared to those women who were taking oral contraceptives or used non-hormonal methods of birth control, the researchers at the University of Texas Medical Branch said. They strongly recommend that patients and their physicians should consider this new information when making a decision about choosing the most suitable form of contraception.

According to Dr. Abbey Berenson, professor in the Department of Obstetrics and Gynecology and director of the Center for Interdisciplinary Research in Women's Health at UTMB, and a main author of the research, the link between DMPA and an increased belly fat, which is a known risk factor for metabolic syndrome, leads to such conditions like cardiovascular disease, diabetes and stroke.

The scientists based their findings on the study that tracked 703 women in two age categories: 16 to 24 years, and 25 to 33 years, who were using DMPA, oral (desogestrel) or non-hormonal (bilateral tubal ligation, condom or abstinence) contraception for three years. Women who initially chose DMPA, but later stopped using this method and selected another form of contraception, were followed for about 2 more years. Throughout the whole duration of the experiment, the experts were recording any changes in the women's body weight and composition. Such factors as age, race, diet and exercise have been taken into consideration.

When later results of all the three groups were compared, it became clear that women who were using DMPA, were more than twice as likely to become obese over the period of three years, compared to users of oral or non-hormonal forms of birth control. However, the study found that the body fat of women who had used birth control methods other than DMPA, slightly increased while their lean body mass (muscle) went down. Researchers said this did not happen among the women who exercised on a regular basis and ate a healthy diet with high levels of proteins.

In Dr. Berenson's opinion, it is not clear yet as to why DMPA causes an increase in weight gain and body fat, and no link has been established between the use of DMPA and calories in a diet, fat consumption or amount of physical activity on body mass changes. The findings seem to contradict the existing theory that gaining weight could be happening due to the drug's perceived effects on an increased consumption of high-caloric diet and less physical activity, and the current research still continues its investigation in order to confirm or discount many possible explanations on this matter, the expert concluded.

The study was supported by the National Institute of Child Health & Human Development.