He should just retire as soon as possible, leave it at that. The only possible way he has gained so much weight over the years without it being his fault has to be Hashimoto's disease expanding at an alarming rate. I had that and gained 20 pounds, but looked normal, not athletic anymore. He has gained about 45-50 lbs, that isn't the disease.
The other plausible thing would be involuntary steroid usage in the mid 90s. Upon leaving the place where it happened, he became susceptible to losing muscle mass if he would ever stop constant training regimen. In 2006 he started letting himself go and has progressively worked less in the off season.