Shivering, weakness, exhaustion sometimes (pancreatectomy)

Hi, my dad had a pancreatectomy a few years ago. Sometime he gets hit by a period of illness where he stays in bed for 24-48 hours. He spends a lot of time shivering, and complains about being cold. He also loses his apetite. Does anyone know why this might happen and how to avoid/remedy it?

 

I've a suspicion it has something to do with his fat/oils intake and possibly him not taking his creon.