I don't think exercise is the issue, we go on long hikes on my days off and even tho I work 10-9 my roommates son is home and we have a huge back yard where my dog and my roommates dog run a play pretty much all day.

I spoke to a vet and they said that it seems normal. Some dogs when they hit age two they settle down a little bit and choose to eat once a day. Either that or he is showing his anger that I am leaving him in the morning. She said he could be rebelling against me going to work and that is why he is only eating when I get home. She said that either way its not a big deal as long as he doesn't stop eating at night.