The birth control method most consistently linked to weight gain is the Depo-Provera shot (the injectable). Combined pills, the patch, the ring, and implants have not shown significant weight gain in clinical studies, despite their reputation. Here’s what the evidence actually says about each method.
The Depo-Provera Shot Stands Out
Depo-Provera, the injection you get every three months, is the only contraceptive with strong, repeated evidence of meaningful weight gain. In one study, users gained an average of 9.3 pounds in the first year and 15.8 pounds over two years. Compared to non-users, that worked out to roughly 6 extra pounds at one year and nearly 12 extra pounds at two years, differences that were statistically significant.
The shot delivers a high dose of a synthetic hormone called medroxyprogesterone acetate directly into your system, where it appears to increase appetite through a direct hormonal effect. Unlike a pill you take daily, the injection can’t be stopped mid-cycle if you notice changes. Once it’s in, you’re along for the ride until it wears off, typically about 12 weeks.
Not everyone gains the same amount. Some people on the shot lose weight, while others gain substantially more than the average. Two factors seem to raise the risk: starting at a higher body weight and being younger. Research on adolescent users found that teens who were already overweight when they started the shot were more likely to gain a significant amount during the first year. If you notice rapid weight gain in the first few months, that pattern tends to continue. Early gain is a useful signal for what to expect long-term.
Combined Pills, Patch, and Ring
The combination pill is the method most people worry about, but large reviews haven’t backed up that concern. A Cochrane review, the gold standard for evaluating medical evidence, looked at trials that compared combined oral contraceptives to a placebo or no birth control at all. The result: no evidence of a causal link between the pill and weight gain. Any changes users experienced were no different from what the placebo group saw.
The same holds for the patch and the vaginal ring, both of which deliver a similar combination of estrogen and progestin. The patch produces an average weight change of just 0.3 kilograms (about half a pound) over 13 cycles. The ring performs similarly or even slightly better. In one comparison, only 1.7% of ring users experienced weight gain over a year, compared to 4.5% of pill users.
So why do so many people swear they gained weight on the pill? A few things are likely happening. People often start the pill in their late teens or early twenties, a time when bodies are still changing and lifestyle shifts (college, new jobs, less activity) can independently cause weight gain. Water retention in the first month or two is also common and can feel like real weight gain, even though it typically resolves. When you’re paying close attention to your body because you just started a new medication, you’re more likely to attribute any change to it.
The Implant
The hormonal arm implant (sold as Nexplanon) releases a low, steady dose of a progestin called etonogestrel. Many people assume it causes weight gain because it’s progestin-only, like the shot. But the data tells a different story. In one controlled study, implant users and a control group had nearly identical weight changes at both one and three months, with no statistically significant difference between them.
A larger trial comparing the implant to the shot and the copper IUD over 18 months found that implant users gained an average of 2.4 kilograms (about 5.3 pounds). That was less than the shot group (3.5 kg) but slightly more than the copper IUD group (1.5 kg). The difference between the implant and the copper IUD was modest, and some of that gain likely reflects natural weight changes over a year and a half. The implant sits in a very different category from the shot when it comes to weight.
Hormonal IUDs
Hormonal IUDs like Mirena release progestin locally inside the uterus, which means very little hormone reaches the rest of your body compared to the shot or even the pill. Because the systemic exposure is so low, hormonal IUDs have not been strongly associated with weight gain in clinical research. Most users don’t experience changes beyond what would happen naturally over time. If weight is a primary concern, a hormonal IUD is one of the most effective options that also carries the least metabolic impact.
The Copper IUD as a Baseline
The copper IUD (Paragard) contains no hormones at all, which makes it a useful comparison point. In the large ECHO trial that followed nearly 8,000 women over 18 months, copper IUD users gained the least weight of any group: an average of 1.5 kilograms, or about 3.3 pounds. That gain likely reflects normal life changes rather than a contraceptive effect. When researchers compared the shot and the implant against the copper IUD, the shot group gained significantly more, while the implant group’s difference was smaller.
If you want to completely eliminate any hormonal influence on your weight, the copper IUD is the clearest option. The tradeoff is that it can cause heavier, crampier periods, especially in the first several months.
How to Think About Your Options
The pattern in the research is consistent: the Depo-Provera shot is the outlier. It reliably causes more weight gain than other methods, and the effect adds up over time. Combined methods (the pill, patch, and ring) don’t appear to cause weight gain beyond normal fluctuations. The implant falls somewhere in between, closer to no effect than to the shot. Hormonal and copper IUDs have the smallest impact.
If you’re already on the shot and noticing weight creeping up in the first three to six months, that’s worth paying attention to. Early weight gain on Depo-Provera tends to predict continued gain. Switching to a different method at that point can change the trajectory. If you’re choosing a method for the first time and weight is a concern, the evidence suggests that most options other than the shot are unlikely to cause significant changes.