Last updated on Jul 7th, 2020 at 01:49 pm

It’s true, your genetic make-up may cause you to gain weight on certain forms of birth control. So what can you do?

“For years, women have said that birth control causes them to gain weight but many doctors failed to take them seriously,” says Aaron Lazorwitz, MD, assistant professor of Obstetrics/Gynaecology and Family Planning at the University of Colorado School of Medicine.

Now we have looked at the genetics and found that the way genes interact with some hormones in birth control could help explain why some women gain more weight than others.”

Genes, weight gain and contraceptives

The University of Colorado School of Medicine study specifically looked at the etonogestrel contraceptive implant.

The rod-like implant, considered one of the most effective birth control methods, is inserted under the skin and contains etonogestrel a kind of progestin that inhibits ovulation.

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The researchers reviewed medical records to calculate weight changes from the insertion of the implant to the time when the women enrolled in the study.

Out of 276 ethnically diverse subjects, they found a median weight change of +3,2 kg weight gained over an average of 27 months of use. The majority (73,9%) of subjects experienced weight gain.


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Who is most likely to be affected?

Drawing on pharmacogenomics, the study of how genes affect a person’s response to drugs, Lazorwitz and his colleagues found that genetic variants in oestrogen receptor 1 (ESR1) among some study participants were associated with clinically significant weight gain.

Women who had two copies of the ESR1 rs9340799 variant on average gained over 13,6 kilograms while using the contraceptive implant when compared to all other women in the study.

For now, there is no way to predict who might be impacted.

The study focused on the etonogestrel contraceptive implant, but it is possible that other birth control drugs could have similar interactions with genes that lead to weight gain.

“It is imperative to better understand how individual genetic variation may influence a woman’s risk of adverse weight gain while using exogenous steroid hormone medications,” Lazorwitz said.

What are the alternatives?

Health care providers can offer counselling about potential weight gain or suggest other forms of birth control like copper IUDs which have no hormones.

“As our understanding of pharmacogenomics in women’s health expands, we can develop individualsed counselling that may reduce the incidence of hormone-related adverse effects, improve patient satisfaction, and help prevent future health risks associated with weight gain,” says Lazorwitz.

Source: University of Colorado Anschutz Medical Campus via

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