Not eating regularly can definitely affect a person.
Has he ever been checked for hypoglycemia?
No, but I find it hard to think he has that:
Symptoms of hypoglycemia include
hunger (he's hardly ever hungry, hence only one meal a day)
nervousness and shakiness (not really)
perspiration (nothing more than usual)
dizziness or light-headedness (no)
sleepiness (no, in fact he has trouble sleeping)
confusion (no, except the normal confusion that comes with being a man... :) )
difficulty speaking (no, but again except what normally comes with being a man... :) )
feeling anxious or weak (no)