This is what the old man did with those same instructions.
That the doctor did not necessarily know what the old man's body was telling him and that was; to say screw the doctor and eat whatever the hell you want. If you were as old as he was, he only had so many days left, and why torture himself with such a ridiculously restricted diet. He decided that he was gonna eat whatever the hell he wanted to eat, regardless as to its affect on how long he was going to live.
He said that if his diet worked just fine for the last seven years. What was the sense in him starving himself for a few more years and to make the doctor happy.
Why in the hell should he stop just for a few more years of painful living. He died of a massive heart attack at age 72, twelve years after bypass surgery.
I am now 78 years old and actually feel better than I did when I was trying to eat off the doctor's menu. I did, however, managed to cut out most of the grease and fat involved in eating pork of any kind. I still managed to take most of the VA drugs prescribed by the VA doctors that's supposed to keep me living a little bit longer. I guess there is still some wisdom in those young doctor’s minds. That they know more about my old body than I do. The old man figured that their diet wasn't working any better than his's diet plan.
I'm not saying that the old man knows better than the doctors do. That the old man's diet plans of eating, whatever you want when you want, increases my lifespan.
I have always considered doctors of any profession, shape or form. Doctors are nothing more than the world's biggest and legal drug pushers. And a lot of them I believe are taking kickbacks from pharmaceutical manufacture.
Years ago after realizing that the VA psych pills were actually causing more problems in my way of thinking than the PTSD did.
I started flushing, the psych pills down the toilet and lying to the shrinks about how well his medication was working. I soon realize that I was far better off, not taking the shrink pills. I now tell the shrinks I will no longer take their prescribed psychological medications that only made my symptoms worse.
It was right about then that I realize the United States government through the VA was using me for nothing more than a pharmaceutical lab rat, in their attempt to figure out which chemical/pill were best for THEM.

Just my two centavos.
Take it as propaganda from my 78 year-old brain.