comment: Your title and explanation of your view really are at odds with each other.
  First 
  
  I've read and heard multiple testimonies about how working out helped someone through depression or provided a gateway to other productive habits and ultimately a better life.
  
  This can be true,
  
  However, I propose that you will not start working out when you are at your lowest.
  
  And this can so be true. 
  You can be depressed, and not be at your lowest point. And being at your lowest point might look very different from person to person. And just because you are better than your absolute lowest point, does not mean you are "overcoming it"
  So you may be not at your worst, and still very depressed, and getting yourself out of your home and working out may help you to continue to get a better mental health.