Effexor is an excellent medication for treating depression
, and it is safely used by many people around the world. That being said, there are some side effects associated with taking the medication. One of the most common side effects is some weight gain, so I think that it is not unlikely that the weight gain you have noticed is from the Effexor.
Importantly, Effexor doesn't produce weight gain primarily by causing the body to handle foods differently. Rather, it works by stimulating the appetite centers in the brain, causing you to tend to eat more than you normally would. This is a helpful insight, because it means that, if you are aware of this tendency to have more appetite on the medication, you can probably in part control the weight gain by paying close attention to what you are eating.
You should also talk to your primary care doctor
or your psychiatrist
, whichever is prescribing the medication for you. They will be able to confirm whether or not, in your case, the Effexor is the most likely cause of your weight gain. If the weight gain is unacceptable to you, you could explore options with your doctor like changing the medication or the dose of the medication.