Harrison Forbes, expert guest on national TV news shows when the topic is animal behavior and pets, has trained dogs for movies and police forces, written the book “Dog Talk” and is developing a pet-talk radio show. The Atlanta Journal-Constitution caught up with him this week to talk about a growing problem among American pets that reflects a similar problem among their owners, pet obesity.

Q: Why should we care if our dogs are fat? What’s the problem?

A: It’s very similar to some ailments people have if you have a fat dog. It shortens their life tremendously and you are setting yourself up for a lot of medical bills. Extra weight on dogs can lead to diabetes, heart problems, joint problems. You are doing your dog a disservice.

Q: If you have a fat dog, what do you do to start slimming it down? What’s the regimen?

A: We are 100 percent responsible for what goes into our pet’s dish. As owners, we have to take responsibility if they get fat, and we need to cut the food and up the exercise. With dogs, they can gain and lose weight pretty quickly. (So start the new regimen and adjust in two weeks or so after checking results.)

Q: And as dogs age?

A: It’s a little counterintuitive. An owner thinks Barney has been a good dog and lived a good life and now he can get fat and lie in front of the fireplace. In truth, he needs to slim down more than ever. It helps tremendously with arthritis (and other illnesses). It’s better to be 2 pounds under what you think he should weigh than 2 pounds over.

And pet nutrition has come so far in the last 10 or 15 years. (Pet food is more nutritious and packed with calories), but some owners still fill up the bowl and let the animal eat out of it all day long. That’s the flip side of super-nutritious food.

Look at your dog, and if you don’t see a slight taper after his rib cage, then your dog is overweight.

And people underestimate the amount of exercise a dog may need. They go for a quarter-mile walk around the block and that barely fits the needs some dogs have. Some dogs can run miles alongside a bicycle, and that’s good for them.