This may be a long shot but it could be linked to an allergic reaction. Lots of dogs suffer from allergies and we may never know because unfortunately they cannot tell us. Has your dog been on any type of medicine or antibiotic that contains steroids? In some cases, steroids has been found to effect dogs in many different ways, including tricking their brains into thinking they're hungry. If your dog does truly believe he's hungry, he may result to eating poop.