Conversation so far:
Who was apart of the casting for the movie?
With the help of producers Alexandra Milchan and Robert Salerno, Schaefer cast Jared Leto as Mark David Chapman.
During filming what was some obstacles if any?
Gaining the weight, he said, was tougher than dieting himself into skeletal shape for his role as drug addict.
Who had to gain weight?
Jared Leto as Mark David Chapman.
Did he feel emotions about having to gain weight?
he said, was tougher than dieting himself into skeletal shape.

Question: Did he loose the weight after the filming was done?
Self-contained rewrite: Did Jared Leto loose the weight after the filming for Chapter 27 was done?