Basically as long as you’re continuing whatever diet and exercise routine you’re on, they shouldn’t pose a problem. Everyone responds to them differently, but I didn’t notice any weight gain when I started antidepressants years ago, albeit I was running very diligently then and for a few years thereafter. I didn’t gain weight until the pandemic hit, and that wasn’t the antidepressants’ fault.
Not all kids of anti depressant cause weight gain. In fact some meds like Wellbutrin actually help in weight loss. Wellbutrin didn’t help my mood swings, I needed to have a different kind of prescription med; also, I am at a high dose due to my current life problems but haven’t gained any noticeable weight due to my current two different kinds of meds.
I would recommend you prioritize and work with your doc to find the correct antidepressant that helps you resolve your mood swings and other related issues. That will also help you feel better and in fact may help with sustaining your success with wt. loss and continue to keep you motivated through college.