But - you gained 50 lbs when you were previously at this nirvana mental and physical healthy state, no? That leads me to believe that you were in neither, otherwise this magic number you seek would have prevented any recidivism. I.e., you woulda had your shyte so tightly together that nothing would have moved it off mark.
So what i think your t is saying, develop healthy body and mind practices where you are NOW, with no other goal than a healthy practice. Then you would be guarded - girded? - against a med change that causes weight gain, for instance, and be conscious and aware and calm enough to do what it takes to nip it in the bud.
For instance - more water, less pop is a good health practice. You are successful every day that happens NOW. You dont have to wait for the future. More such healthy practices will get you where you want to be.