wont eat

Question
Recently, by recommendation from the vet, we switched our dog's food to fish and potato. He was eating it and loving it and then all of a sudden now he won't eat it. The only time he eats is when he is eating human food. We tried putting some of our food mixed in with his food, but he licks it all off and spits it out. He makes a huge mess doing this as well.
Here are some of the reasons I was thinking this was happening and if you could let me know if any of these are right or if there is another reason..
-he's not getting enough walks and therefore his stomach is staying full so he isn't hungry
-he has been eating human food too much (he gets into the garbage a lot) and so he has higher expectations now
-he's getting older (he's about 5 1/2) so his stomach can't handle it
-my boyfriend thinks it's got to do with the fact that we just recently took down the baby gates that were blocking him from the kitchen because he just jumped over them or always got in somehow and ate everything anyway, but I don't see how that could be relevant

I was thinking of trying something like tuna juice in his food so that it would soak it up and he wouldn't be able to lick it off and so if he wants the tuna juice he's got to eat the food. Would this be a good idea?
Thanks a bunch.

Answer
Most of your ideas may be part of the problem.  Is he overweight?  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them.  Each dog is different.  Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx

The worst thing you can do is to bribe a dog with rich foods into eating more than it needs. Instead, Put down the dish with what the dog should eat, and give it 15 minutes to eat. Then take it up. Do not give it anything to eat until its next scheduled meal. In a few days, it should be eating what it needs. Continue to check its ribs and adjust the food as needed. This is not easy. I had a Shepherd go 3 days on a few nibbles. I was a wreck, but she was fine. It is almost unknown for a healthy dog not to eat what it needs. Unfortunately, in too many cases, it is less than the package says, and less than the owner thinks the dog should have. Many dogs are quite good at holding out for tastier chow. Like kids, sometimes it calls for tough love.

He really needs to be eating his dog chow and very little else.  The dog chow change was to work around allergies?  If so, much of your human food may contain the same allergens.  Many foods are hard on a dogs liver and pancreas.  

If he is stealing food when you aren't around, you may need to crate him.  A mousetrap is very effective in making a dog leave something alone.  Most dogs will stay away from anywhere they were surprised by a snap.  The best part is that it is not you that is correcting the dog.  It works whether you are around or not.  The mousetrap is very patient and is always on task as long as you reset it.

Better than mousetraps when you aren't around is the crate.  Other dogs may not be as bad as the young Labs I am plagued with.  Still your house and dog will be much safer with the dog in a crate when you are away.  The dog may be happier in its den than loose in the house.  It relaxes, it feels safe in its den.  It rests, the body slows down reducing the need for water and relieving its self.  Dogs that have been crated all along do very well.  Many of them will rest in their crates even when the door is open.  I think the plastic ones give the dog more of a safe, enclosed den feeling.  They are harder for dogs to open too.  Metal ones can be put in a corner or covered with something the dog can't pull in and chew.  Select a crate just big enough for the full grown dog to stretch out in.

Leave it some toys.  Perhaps a Kong filled with peanut butter.  Don't leave anything in the crate the dog might chew up.  It will do fine without even any bedding.  You will come home to a safe dog and a house you can enjoy.

A dog that has not been crated since it was little, make take some work. Start out just putting its toys and treats in the crate.  Praise it for going in.  If you have been able to trust it with any bedding, put that in the crate. Feed it in the crate.  This is also an easy way to maintain order at feeding time for more than one dog.