Veterinarian Steve Thompson of Purdue University's Veterinary Teaching Hospital is tactful when he tells a pet owner an animal is overweight.

"I uses phrases like 'a little heavy,' " he says. "I try not to use the word 'fat.' " And he really, really tries to stay away from "obese."

Owners often don't take the news well and may not even believe him.

I'll be happy sometimes if an owner will agree that the dog just shouldn't gain weight," Thompson says.

Granger veterinarian Kari Hatch of Kryder Veterinary Clinic faces the same disbelief and denial from pet owners. The problem is, she says, so many pets these days are overweight that our perception of what's a healthy weight has been skewed.

"A lot of people think their fat dog is healthy and an in-shape dog is too thin," she says. But, "the majority of dogs we see by far are overweight," she adds. This goes for cats, too.

Even if the news is hard to take, the truth is that many American pets, like their owners, are too heavy.

The Association for Pet Obesity Prevention, a group of veterinarians concerned with weight problems in animals, estimates 45 percent of all pets in the United States are at least overweight, and that 25 percent are obese.

Hatch says she's heard 80 percent of dogs are overweight and she believes it.

Just as with humans, maintaining a healthy weight largely is a matter of paying attention to nutrition and exercise.

Is my pet fat?

Ideally, veterinarians should alert owners if a pet is overweight. But there are rules of thumb that owners can use to gauge weight, Thompson, the director of Purdue's Pet Wellness Clinic, says.

"You don't want to be able to see the ribs, but you do want to be able to feel them in both dogs and cats," he explains. That means if you run your fingers alongside your pet's ribs using slight pressure, you should be able to feel the ribs.

Also, if you're looking down on the animal from above, the area just below the rib cage should tuck in, giving the animal an appearance of a waist, Thompson says. If the area below the rib cage is wider than the rib cage, chances are, the animal is overweight.

From a side profile, an abdomen that hangs down or jiggles also indicates a weight problem in most cases.

How much food is right?

The guidelines above can help determine how much to feed a pet, says Thompson, who calls this method "feed to feel," referring to the goal of easily feeling an animal's ribs.

Pet food labels tend to be "generous" in recommended portions, Thompson says, and there are other issues to consider, especially metabolism.

"There is a variability in metabolism among pets," Thompson says. "It drops after spaying or neutering."

Thompson and Hatch both recommend measuring food precisely by finding a measuring cup or scoop that holds exactly how much food the pet needs.

To help an animal lose weight, Thompson recommends cutting back food by no more than 10 percent at a time. Giving an animal two scheduled feedings per day can help stave off hunger, he adds.

"I go pretty slow," he says. "We still allow treats because of the animal-humanbond, plus cutting treats almost never works. That's part of how people interact." But owners can choose smaller biscuits or cut treats in half.

And be careful of snacks, Hatch recommends. "Consider them as you would a candy bar for your kid," she says. "You wouldn't give your kid a handful of candy bars."If you share human food with pets, make sure it's healthy food and not junk food or fat from meat. If anything, Hatch recommends lean meat or chicken. Crunchy baby carrots and green beans are great because they have few calories and no carbs.

Also, owners should subtract extra calories from an animal's daily caloric needs.

Dog exercise

Dogs and cats have different exercise needs that trace back to the hunting methods of their wild ancestors.

Dog packs would expend a lot of energy and cover a lot of territory when hunting a big animal that would be shared among each member of the pack, Thompson says.

Though exercise needs for modern, domesticated dogs are different, they still need longer sessions of exercise than cats do.

"We want a dog and the owner to have 20 minutes of exercise two to three times a day," he says, though he'd prefer 40 minutes a day.

"I would like them walking, moving," during that time, Thompson adds. "I think the people that have fenced-in yards where the dog does all the exercise itself, a lot of those dogs aren't appropriately stimulated."

(Additionally, studies have shown it's better for a dog's bladder to take the dog out at least three times a day over twice a day, Thompson says.)

If a dog has been sedentary, it's important to ease the pooch gradually into exercise, Hatch stresses.

"A lot of people think dogs are perpetually fit," she says. "They'll take the first nice day and play ball or run for a long time and the dog gets injured. It's sort of like the 'Weekend Warrior' mentality in a person."

As well as walking, fetching can fulfill a dog's exercise needs during bad weather or at times an owner can't walk it

And if keeping a dog's weight regular isn't enough incentive to get it out for a walk, think about behavior, Thompson urges.

In studies of dogs with behavior problems, less-active lifestyles and confinement were linked with bad behavior, he says. Those include behavior problems, fear behavior, separation anxiety and destructive behaviors.

Exercising your cat

Yes, it can be done, Thompson says, explaining the evolution of it.

"Cats spend 20 to 22 hours a day resting," he says. "For a couple hours, they walk around and change bedding and napping sites." Must be nice.

Wild cats, including the ancestors to modern house cats, are visual hunters. They use a lot of their energy watching their prey attentively, sprint for a short distance after it, and then pounce.

So, following cat instinct, getting a cat to exercise is different from hooking it up to a leash and taking it for a walk (though some cats enjoy that).

"It's challenging to get cats to exercise, but one of the key things we work on is you can teach cats to fetch," Thompson says.

It's easiest to teach cats to fetch during the first two or three months of their lives, but it's not impossible to teach an adult cat.

Another way to stimulate a cat into exercising is with one of those feathers/toys attached to a string on a rod. "This is something where an owner doesn't have to do a lot of exercise," Thompson says.

Balls, flashlights and even crinkly paper can encourage cats to play.