6 month Golden Eating habits

Question
Up till this week we were on a routine everyday!!  Up at 5 and outside then inside to be fed.  He used to eat his food within 5 mins and now seems to want nothing to do with it till he has to eat it.   This is the same at night as well.  I don't want to leave food out and let him graze, thats how they get fat.  Please help me understan the sudden change in behavior and how to get him back on track.

Answer
I had the exact same problem until two weeks ago after he got neutered. If you are planning, get him neutered soon. But when he didn't eat, i tried using dog food sauce.(found at petstores) If not, try mixing with wet dog food.(But careful, some dogs get diareaha)