Weight Change and Hormonal Contraception: Fact and Fiction

Mags E Beksinska; Jenni A Smit; Franco Guidozzi

Disclosures

Expert Rev of Obstet Gynecol. 2011;6(1):45-56. 

In This Article

Limitations in Existing Research

Weight gain and contraceptive use research faces many inherent obstacles. In adolescents and young women we can anticipate weight gain as part of normal growth. Adult women also generally gain weight over the years.[77] A control group of nonusers of hormonal contraception is therefore essential in a study looking at weight change, yet few studies have included this group. Few placebo randomized controlled trials are available, and this is in part due to the complex and ethical issues that present in a trial of this nature.[14]

Because weight gain can cause discontinuation (perceived or real), many women may leave a trial or be lost to follow-up and this could bias the results, as women remaining in follow-up may not experience this side effect or are willing to accept some weight gain. Follow-up of adolescents may be challenging as contraceptive discontinuation rates are high. In one study of adolescents, almost half (46%) of COC users and over one-third (37%) of DMPA users had discontinued the study by 18 months.[26] In a more recent study that included a mix of adolescents and young women using COCs or DMPA with a mean age of 24 years, 73% of women did not complete the 3-year study for a number of reasons.[18] Although many were lost to follow-up, 19% wanted a different method of contraception. This indicates the importance of following-up women beyond discontinuation, not only to collect reasons for method discontinuation but also to monitor weight changes. This would give us a better picture of reversal of weight gain, in particular in users of DMPA.

Reporting weight gain has also differed across studies. Reporting of mean weight change may not be useful when women's weight can decrease, increase or remain stable. It is important to report the percent change of weight from baseline, and in addition present more detail on subgroups of different baseline weights and the proportion of women gaining and losing weight. Broad classification of what is normal, overweight and obese has varied between studies, with different cut-offs for BMI used to define weight groups. In some cases these groups are collapsed and normal and overweight individuals are combined, or overweight and obese individuals are combined. The proportion of adolescents in the obese category has often been small, thus making it difficult to draw conclusions.

A further limitation is the lack of evidence on newer hormonal methods, or those not as widely available. For example, there is minimal information on weight changes in NET-EN and POP users, although these methods have been available for many years.

It is surprising that so little is mentioned about dieting in studies investigating weight change. Data from the National Longitudinal Study of Adolescent Health (Add Health) in the USA found that approximately half of female adolescents in this survey were currently trying to lose weight.[78] One study reporting on the dieting habits of hormonal contraceptive users asked women if they had dieted since their last visit. In this study approximately 10% of women were dieting between visits across all study groups.[28]

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