Please do not be so close minded. Everyone experiences things- especially mental illness, differently. I have always struggled with mental illness, you could say I am high functioning (research this before spewing uneducated opinions!). Personally if anything phycologists have taken my symptoms more severely because I upkeep such a healthy lifestyle and (was) still struggling. I am on SSRI's now and they have absolutely helped, maybe you are not getting the right treatment if you are saying "What I'm saying is if you're depressed enough to take antidepressants you wouldn't even think about staying in shape" you realise they are supposed to help you right? what do you think the point of them is if not to lull symptoms such as a lack of motivation?
Anyways I suppose you struck a nerve with me because it's always been very personal to me that no matter the effort I put into preventing my major depressive episodes I could not prevent them.
Free yourself from your mind! You can work out, you really can do whatever you want unless you are wheelchair-bound. You are very privileged having been able to have access to the support to get anti-depressants and to be criticising others on the internet on the first place.
#lovewins I wish the best for you OP and overcoming an unhealthy lifestyle