That is a tough one because even if you bought all the right foods, he could go out and head to the nearest fast food or whatever it is he loves to eat.
I don't think there is anything you can do since he is a grown man but I understand what you are saying--you have worked hard and you do not want to lose him again to his health issues.
Take the car keys away but not tell him???!!!!!
The Bomb: 08/05 H moves out: 06/2006 H moves back: 01/07 & Out again: 01/07 H moves back: 03/08 & Out again: 04/08 H moves back: 05/09 & Out again: 07/09 Divorced 08-12 Kids: 22, 20, 19