The Question of Weight Gain and Contraception
For many individuals choosing a contraceptive method, potential side effects are a primary concern, with weight gain frequently topping the list [1.11.1]. Non-estrogen birth control options are often sought by those who cannot or should not take estrogen [1.3.3]. These methods include progestin-only contraceptives and the non-hormonal copper IUD. While the fear of gaining weight is a common reason for avoiding or discontinuing hormonal birth control, scientific evidence presents a nuanced picture that largely debunks this as a universal side effect, though some notable exceptions exist [1.2.1, 1.2.2].
Understanding Non-Estrogen Birth Control Methods
Non-estrogen options work by using the hormone progestin or no hormones at all. They are available in several forms:
- Progestin-Only Pills (Minipills): Oral contraceptives that contain only progestin and must be taken at the same time each day [1.4.3].
- The Contraceptive Injection (Depo-Provera): An injection of the progestin depot medroxyprogesterone acetate (DMPA) given every three months [1.6.5].
- The Contraceptive Implant (Nexplanon): A small, flexible rod inserted under the skin of the upper arm that releases a continuous low dose of progestin [1.10.1].
- Hormonal Intrauterine Devices (IUDs): Devices like Mirena and Kyleena are placed in the uterus and release a small amount of progestin locally [1.5.2, 1.8.4].
- Non-Hormonal Copper IUD (Paragard): A hormone-free IUD that uses copper to create an inflammatory reaction in the uterus that is toxic to sperm [1.5.4, 1.8.4].
The Scientific Evidence: A Method-by-Method Breakdown
The link between progestin-only contraceptives and weight gain is not uniform across all methods. Large-scale reviews and studies have found that while a strong association exists for one particular method, the evidence for others is weak or nonexistent.
The Birth Control Shot (Depo-Provera)
Of all non-estrogen methods, the Depo-Provera injection has the strongest and most consistent link to weight gain in research studies [1.2.4, 1.10.3]. A study with over 3,900 women showed that users gained an average of 5.4 pounds after one year, 8.1 pounds after two years, and 13.8 pounds after four years [1.6.2]. Another study found this weight gain was primarily due to an increase in body fat mass, not just water retention [1.6.4]. The mechanism may be related to progestin's potential to increase appetite or its glucocorticoid-like effects, which can alter how the body stores fat [1.2.2, 1.6.4]. However, not everyone experiences this; some individuals report no change or even weight loss [1.6.3].
Implants, IUDs, and Minipills
For most other progestin-only methods, the data does not show a significant causal link to weight gain. A major Cochrane review concluded there is little evidence that progestin-only contraceptives (excluding the shot) cause significant weight gain, with most studies showing an average gain of less than 4.4 pounds (2 kg) over 6 to 12 months, which was similar to weight gain in control groups not using hormonal methods [1.3.1, 1.7.3].
- The Implant (Nexplanon): While weight gain is listed as a potential side effect, research has not found a conclusive link. Studies show that users gained similar amounts of weight as non-users over the same period [1.10.1].
- Hormonal IUDs: Because the hormone in these IUDs acts locally in the uterus, very little is absorbed into the bloodstream. Studies show minimal weight gain, with one reporting an average of about 1.59 lbs after 12 months, concluding it could contribute to low levels of weight gain [1.5.5].
- Minipills: Progestin-only pills have not been shown to cause weight gain in major studies [1.7.2]. Any perceived change is often minor and not significantly different from natural weight fluctuations over time [1.7.1].
- Copper IUD: As a non-hormonal method, the copper IUD does not cause weight gain related to hormonal changes [1.5.1, 1.5.2, 1.5.4].
Comparison Table of Non-Estrogen Methods
| Method | Hormone | Reported Association with Weight Gain | Other Common Side Effects |
|---|---|---|---|
| Depo-Provera Shot | Progestin (DMPA) | Most likely to cause weight gain; average gain of 5.4 lbs in the first year [1.6.2]. | Irregular bleeding, headaches, bone density loss (with long-term use) [1.6.1, 1.4.2]. |
| Implant (Nexplanon) | Progestin (Etonogestrel) | Unlikely; studies show no significant difference compared to non-users [1.10.1]. | Irregular bleeding (most common), headaches, breast tenderness [1.10.2, 1.4.3]. |
| Hormonal IUD | Progestin (Levonorgestrel) | Unlikely; low hormonal dose acts locally. May contribute to very low-level gain [1.5.5]. | Irregular bleeding/spotting, lighter or no periods, cramps [1.8.1, 1.8.3]. |
| Minipill | Progestin (Norethindrone) | Unlikely; studies do not show a causal link [1.7.1, 1.7.2]. | Irregular bleeding, headaches, nausea, breast tenderness [1.4.1, 1.4.4]. |
| Copper IUD | None | No association with weight gain [1.5.1]. | Heavier, longer, and more painful periods, especially initially [1.8.2, 1.8.4]. |
Managing Weight Concerns
Weight gain is complex, and people tend to gain weight over time regardless of contraceptive use [1.3.1]. Lifestyle factors such as diet, exercise, stress, and age play a significant role [1.5.1, 1.9.1]. If you are concerned about weight gain while on birth control, experts recommend:
- Maintaining a balanced diet rich in fruits, vegetables, and lean proteins [1.9.2].
- Engaging in regular physical activity, aiming for at least 150 minutes of moderate activity per week [1.9.1].
- Staying hydrated and reducing intake of sugary drinks [1.9.1].
- Tracking your weight and symptoms before and after starting a new method to identify true changes.
- Speaking with your healthcare provider to discuss your concerns. They can help rule out other causes and suggest a different birth control method if needed [1.2.2].
Conclusion
In summary, the fear that all non-estrogen birth control causes significant weight gain is largely unfounded. With the exception of the Depo-Provera injection, most scientific evidence indicates that progestin-only methods like the implant, hormonal IUD, and minipill do not cause a significant increase in weight for the average user compared to natural weight fluctuations. The non-hormonal copper IUD has no impact on weight. Individual experiences can vary, and open communication with a healthcare provider is the best way to find a contraceptive method that aligns with your health needs and personal concerns.
For more detailed information from a leading authority on women's health, you can visit the American College of Obstetricians and Gynecologists (ACOG) [1.4.2].
