As mammals, dogs process foods in a way that is somewhat similar to the way we do. Sugar, in the form of glucose, is carried to all of the body’s cells via blood. Your dog may not directly be ingesting sweets, but glucose can come from carbohydrates since carbs consist of long chains of glucose, which breaks down quickly in the body and can raise blood sugar levels.
Colleen Paige -- author of The Good Behavior Book for Dogs: The Most Annoying Dog Behaviors ... Solved! -- believes that dogs may get a sugar high that “can cause a dog to be hyper and unfocused.” She thinks that, in many cases in which dogs appear to be ill-mannered and uncooperative, the dog’s behavior could actually have been influenced by diet.
Similar to what we experience, dogs can suffer a sugar low after the high, causing dogs to become “sleepy, lethargic, moody and irritable,” says Paige. If your dog is not eating a high-quality food with good ingredients, your pet could experience a regular daily cycle of extreme highs and lows. Over time, problems like diabetes could result, given that the body has to work harder to process excess glucose.
Paige urges owners to steer clear of dog foods with excess sugar and carbs, not to mention preservatives, artificial coloring, artificial flavorings and other “no-no” ingredients, as she calls them.