Does Nexplanon Cause Weight Gain?
Weight gain is listed as a potential adverse effect of Nexplanon, but the best available evidence shows that clinically significant weight gain does not consistently occur with the etonogestrel implant when compared to non-hormonal contraception. 1
Evidence from Guidelines
The American Academy of Pediatrics acknowledges that weight gain is among the reported adverse effects of the etonogestrel implant, though these effects are "not common" compared to the primary side effect of irregular bleeding. 1 However, this guideline also emphasizes that adult data suggest women with obesity are not more likely to have significant weight gain with progestin-only contraceptives like implants. 1
Evidence from Clinical Research
Most Recent High-Quality Study (2019)
The strongest evidence comes from a 2019 study specifically examining adolescents and young adults using Nexplanon over a mean follow-up of 24.5 months. 2 This study found:
- Mean weight change for ENG users was +3.6 kg versus +3.1 kg for matched controls (P = 0.43) - not statistically significant 2
- Mean BMI change was +1.3 in cases versus +1.0 in controls (P = 0.204) - not statistically significant 2
- Only 3 out of 43 patients (6.3%) who removed the implant early cited weight gain as the primary reason 2
Supporting Evidence from Body Composition Studies
A 2017 prospective cohort study measuring actual body composition (not just weight) found no significant differences in weight or body composition changes between ENG implant users, LNG-IUS users, and copper IUD users over 12 months. 3 This is particularly important because it measured fat mass and lean mass directly, not just total weight.
A 2013 study from the Contraceptive CHOICE Project showed that while unadjusted models suggested weight gain with the ENG implant, adjusted models found no difference in weight gain when compared to copper IUD users. 4 The mean weight change was 2.1 kg for ENG users versus 0.2 kg for copper IUD users, but this difference disappeared after adjustment for confounders. 4
Important Racial Considerations
Black race was consistently identified as a significant predictor of weight gain among contraceptive users, independent of the contraceptive method used. 4, 3 This means that Black women may experience more weight gain regardless of whether they use hormonal or non-hormonal contraception, making it difficult to attribute weight changes solely to the implant. 4
Clinical Context and Variability
The 2014 Nigerian study showed broad individual variability in weight changes with Nexplanon use: 5
- 38.6% of women lost weight or had no net weight change 5
- 61.4% gained weight, but amounts varied widely (most gained only 1-5 kg) 5
- Initial body weight was the most significant predictor of final body weight (83.5% predictive value) 5
Practical Counseling Points
When counseling patients about Nexplanon and weight:
- Inform patients that weight gain is a reported side effect, but controlled studies show no consistent, clinically significant difference compared to non-hormonal contraception 4, 3, 2
- Emphasize that individual responses vary widely - some women gain weight, some lose weight, and many experience no change 5
- Explain that any weight changes are likely influenced more by baseline weight, race, age, and lifestyle factors than by the implant itself 5, 4, 3
- Note that concerns about weight gain should be balanced against Nexplanon's exceptional efficacy (0.05% failure rate) and high continuation rate (84% at 1 year) 1
Common Pitfall to Avoid
Do not dismiss patient concerns about weight gain simply because studies show no significant average difference. Individual patients may experience weight changes, and these concerns are valid reasons for shared decision-making about contraceptive choice. However, the evidence supports reassuring patients that most women using Nexplanon do not experience clinically significant weight gain attributable to the device itself. 4, 3, 2