There are a few different types of birth control. A small number of these can have weight gain as a possible side effect. This means that it does not happen to everyone who uses that method.
Have a look at the sexandu page on different birth control methods. They list how they work as well as any possible side effects like weight gain.
I would just recommend talking with your health care provider about what method would work for you. They would be able to see what side effects you are concerned about, your medical history and what preference you have in how it is used.
Also have a look at the Options for Sexual Health website for different Birth Control Options. They specialize in birth control and have clinics around BC.
They also have the Sex Sense line on 1-800-SEX-SENSE if you would prefer talking with someone directly about your personal situation and any concerns you may have around birth control.
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