Also, it really depends on how you want to look at this.
The best answer to this is either SHAQ or Eddy Curry depending on how you want to define this. Shaq was damn near 400lbs from rumored reports during that late 90's-Early 200's run, but not

his entire career.
Eddy Curry on the other hand seemed like he was always out of shape, but did have a productive career. He had 6 solid seasons in double figures in PPG and was almost selected to an all-star game when he was on the knicks.
edit: I guess you can also throw older Charles Barkley in this convo as well. We need rules, thread is too open.