Brief Answer:
Detailed below.
Detailed Answer:
Hello!
Thank you for the query.
There might be few reasons of such symptoms, all associated with his diet and regular alcohol intake. 
This factors can cause 
pancreas inflammation, stones in bile ducts and stomach issues like 
peptic ulcer.
Pancreas and bile ducts issues usually give upper middle pain, which appears after a meal and radiates to the back. Nausea and 
vomiting is very often.
Peptic ulcer can give similar symptoms however the pain usually does not radiate to the back.
At his age, there is necessary to rule out cancer of the stomach, pancreas, liver and large intestine. That is why, even if he seems to be in great health he needs some tests.
It is necessary for him to have blood work, liver tests (AST,ALT,GGTP), amylase, urine amylase, abdominal 
ultrasound, gastroscopy and 
colonoscopy. For pancreas diagnostics, abdominal CT should be also considered.
Hope this will help. Feel free to ask further questions.
Regards.