A depressed person’s view is completely warped from reality. One of the key parts of cognitive behavioral therapy is slowly training yourself out of horribly inaccurate views about yourself and the world.
I get depressed (I take SSRIs, too) because we live in 2021 and I see people taking advantage of each other on a daily basis, killing each other over things that don't matter. I have a front row seat to watching some of the world's greatest minds argue over semantics. That's the real world. That's realistic.
Whether you take that to nihilism is something else. I know the pit of despair depression you are talking about but it is a spectrum.
The flipside is my struggle with weight.
I (ill-advisedly and not entirely purposefully) was off of my SSRIs for about a week while I was already mildly depressed about my weight gain.
I was much more depressed about it in that week, and I definitely feel like this was because I was forced to deal with the reality of the situation, whereas on my SSRIs I was more easily able to push it out of my mind. There are times when your depression is driven by tough reality (for me, that diet, exercise and un-ending hard work are needed for weight loss), and the only way to become happy in spite of this is either commit to the work or choose to ignore it.
When it comes to your weight, it's not about pushing the thought of your weight gain out of your head. It's about combating the lies that you are telling yourself about your weight gain: that it means you are lazy, unlovable, disgusting, etc. The way you be happy in spite of your weight gain is not to either commit to the work or choose to ignore it (although for peoples health it's definitely good to commit to the work) but is rather to not view your weight gain as a statement of your self. You are not your problems, you are not your weight.