This seems to be a case of Obsessive Compulsive Disorder, where his body produces excess adrenaline production - a stress hormone - and that forces him to focus on the "enemy" and potential dangers in life.
Excess adrenaline may be due to insulin resistance which is one of the causative factors in diabetes or a pre-diabetic condition, called popularly hypoglycemia. People with this condition can suffer from anxiety and nervousness and fastidiousness. Concentrating on details.
I suggest that the doctor test him for diabetes and if he is not diabetic, then he should be tested for hypoglycemia, which is a different kind of test. See:
Testing for Hypoglycemia
Obsessive Compulsive Disorder (OCD) and Nutrition at.
Since the hypoglycemic diet is a natural diet, he should not have any problems adopting this.