I would definitely try losing the weight first. Have you tracked your eating, calculating at least the calories? If you're regularly eating well over what you can burn in a day, then obviously one must eliminate some foods, preferably high calorie low nutrition foods. Sometimes we think we're not eating much (or that many calories), but we sometimes are. Even habitually.

I know people like to explore all kinds of diets, but I really do recommend at least initially getting a clear idea of what you really eat.

If interested, there are good websites for calculating how many calories are needed for weight loss, or even maintenance. They take daily activity level, age, gender, and starting weight in mind. One is at Calorie Calculator I don't recommend "extreme" weight loss calorie intake. That is usually not easy enough to sustain and leads to failure.

There are great calorie counter sites available for free. I, personally, recommend MyFitnessPal. Their free option is more than useful enough for me. They also have an app with a free option. Google them or a similar, if interested.

If a bona fide attempt to diet (over at least a first month) yields less than a 3 lb loss, then I guess I would talk seriously with your psychiatrist about medications that are more weight friendly. By "bona fide", I mean actually eating few enough calories to be in the usual weight loss range. You may also want to talk with your therapist about any possible psych obstacles that prevent effective dieting. Again, if it is truly determined that the medications are the only obstacles, then surely a medication change should likely be considered. I'm just concerned that sometimes people put all of the blame on medications, when there are indeed other factors that play into weight gain.