I would say to write out any resistances etc to what this medication is doing to your body. Because if it is in fact something you see that you do require, then for example I'd write out why it's best to yes, stick with the medicine, and to accept the temporary consequences/side effects that it entails for starters so that you are clear that you require this and what it is doing to you, and then from there I think you can more easily/directly make a decision as to lose the excess weight and such. Because not being clear in one's relationship to medicine, or anything, can increase the effects, or here the side effects, so would be for example worsening the situation by attaining more weight than one would get if they were not participating within the mind.
Other than that, I'm personally a fan of the simple things. Like walking, eating healthy - to stay fit/healthy. I have not tried diet plans or supplements for appetite control/weight loss. Something like appetite control sounds like something that again, you could write out, to see if you're eating as the mind as opposed to eating as the physical. Because the physical's nutrional needs are certainly different to the mind's nutrional (or lackthereof) needs!